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History of Communications-Electronics in the United States Navy, Captain Linwood S. Howeth, USN (Retired), 1963, pages 297-312:


Development  of  Underwater  Sound  and  Detection  Equipment


Most major wars have caused an acceleration in the development of weapons systems or devices. This was particularly true during the past two global conflicts. The increased mobility of man and the increasingly rapid dissemination of voluminous news reports resulted in public interest being centered on the development of many of these systems and devices. During the past World War, first it was radar, then rockets, followed by V-bombs and then, transcending all others, the atomic bomb. In World War I, the development of submarine tactics and the destruction of Allied merchant shipping by the Germans was of such a magnitude as to cause the gravest apprehension regarding our ability to provide the necessary logistic support to prosecute the war on the European Continent. All measures taken to combat this menace were followed by the public with intense interest but, since it was necessary to seek out the enemy submarines before they could be destroyed, none was followed with closer interest than was the development of means of detecting these destructive and elusive undersea vessels.


The final successful development of underwater sound and detection devices was the result of two things: man's inquisitiveness concerning the unknown ocean depths; and his desire to provide a longer range method of communication while embarked upon water. The first realization that sound carried through water is lost in antiquity. Long ago the Ceylonese signaled each other while at sea by striking an earthen "chatty" which produced a sharply percussive sound that could be heard for several miles by an ear held against the bottom of a boat.1 About the end of the 15th century, Leonardo da Vinci, a seminal engineer and physicist, as well as painter, anatomist, and inventor, noted that if one end of a tube was placed in water and the other to the ear, a person on a stationary vessel could hear the movements of other vessels in the immediate vicinity.2 In 1826, Colladon and Sturm, in endeavoring to obtain the velocity of sound in water, used a hammer to strike a submerged bell. The sound waves emitted were received 10 miles away by an ordinary ear trumpet the mouth of which was covered by a diaphragm and held underwater.3 Early in the 19th century the British scientist, Tyndall, was provided a liberal grant to investigate the reason why fog signals in the air could not always be heard or, when heard, could not be accurately located.4 Later Henry, our noted scientist, was commissioned to conduct a similar study by the U.S. Government. Both arrived at the conclusion that fog signals in the air were untrustworthy.5
    Interest in what lay beneath the seas is as old as the memory of man. An Egyptian artist of the 12th dynasty, more than 2,000 years before the dawn of Christianity, left a graphic description of an early sounding lead. Later, Herodotus described sounding the Nile with a plummet. The Greek, Eratosthenes of Alexandria, who demonstrated that the earth was a sphere approximately 25,000 miles in circumference, indicated that he was aware of large variations in depth in the Mediterranean. Posidonius, his successor, charted the Sardinian Sea about 150 B.C. During the period between the decline of Greek culture and the end of the 15th century little concern is recorded of man's interest in the structure of the world or in oceanography, although there are numerous indications that the lead and line were used in the interests of safe navigation. The voyages of Columbus reawakened interest concerning the earth and its navigable waters. This interest finally culminated in Magellan's circumnavigation of it. The first recorded evidence of the dipsey lead (weighing between 30 and 100 pounds) is found in Capt. John Smith's "Seaman's Gram," published in 1627. Before the development of more practicable methods it was used for deep-sea soundings up to 100 fathoms. A lighter lead, weighing between 7 and 14 pounds, was, and occasionally still is, used for shallow-water soundings.6
    About 1825, Jean Francois Arago, astronomer, engineer, and physicist, suggested that propagated sound waves could be utilized to measure ocean depths. This was attempted in 1854 by Lt. Matthew Fontaine Maury, USN. He exploded petards in deep ocean, hoping to receive the echo, but failed because he did not use a direct connection between the ear and the sea.7
    Oceanography was brought into existence by Maury who, because of his work in this field, became known as the "Pathfinder of the Seas." In he wrote his "Physical Geography of the Seas," in which he stated:
Until the commencement of deep-sea sounding, as now conducted by the American Navy, the bottom of what the sailors call "Blue Water" was as unknown to us as the interior of any of the planets of our system. Ross and Dupetit Thovars with other officers of the French, English and Dutch Navies had attempted to fathom the sea, some with silk threads, some with spun yarn and some with the common lead line used in navigation. All these attempts were made on the supposition that, when the lead reached the bottom, either a shock would be felt or the line, becoming slack, would cease to run out. The series of systematic experiments recently made upon this subject shows that there is no reliance to be placed on such a supposition.
    Maury, an officer of insatiable scientific curiosity, was placed in command of the Depot of Charts and Instruments of the Bureau of Ordnance and Hydrography in 1841. This was the predecessor of our famous Naval Observatory and the present Navy Hydrographic Office. While in this position he instituted the taking of exact measurements of ocean depths and composition of ocean floor by ships of the Navy. These were early of immeasurable value in the laying of the first transatlantic telegraph cable. Hydrographic investigations of the Navy soon became recognized among the foremost works in oceanography and spurred the interest of many persons in this field.8
    Maury's method, utilized by the Navy, consisted of dropping a cannonball attached to 10,000 fathoms of line, marked every hundred fathoms, and played out from a reel. The depth was determined by the time it took the ball to descend each hundred fathoms and, when the reeling-out for a specific 100-fathom segment exceeded the rate previously established, it was concluded that bottom was reached. His method was improved, in 1854, by one of his assistants, Midshipman J. M. Brooke, USN, by the addition of a bottom-sampling device and a means of releasing the ball when it reached bottom in order to facilitate recovery of the sounding line.9
    In 1875 the British scientist, Lord Kelvin, who was associated with Mr. Cyrus Field in the laying of the first transatlantic cable, developed the first practicable pressure tube for measuring depths of less than 100 fathoms. This was improved by Captains Tanner and Blish of the U.S. Navy and later by Capt. G. T. Rude and Mr. F. Fischer, of the U.S. Coast and Geodetic Survey.10
    The Maury-Brooke deep-sea sounding equipment was improved by Comdr. (later rear admiral) C. D. Sigsbee, USN. His equipment utilized piano wire of great tensile strength as the sounding line and both it and the dipsey lead were hauled in by power. It became standard equipment in the Navy and remained so until outmoded by electronic echo-sounding equipment.11
    During the last decade of the 19th century Prof. Lucian Blake, of Kansas, made numerous investigations with an underwater bell and microphones in endeavoring to develop an underwater signal system which could provide mariners with warnings of dangers to navigation. The U.S. Lighthouse Board compiled a complete report on his investigations in 1899, after which the matter was dropped.12
    A short time later, Mr. Arthur J. Mundy, unaware of the work of Blake, began conducting experiments at his residence on Cape Ann, Mass. He also utilized the bell and microphone. He was assisted by Prof. Elisha Gray and Mr. Joshua B. Millet. Their accomplishments led to the formation of the Submarine Signal Co. in 1901. This was the first commercial enterprise organized to conduct underwater sound research and to develop equipment to be used for increasing safety of navigation.13


The major part of the Submarine Signal Co.'s early development work was directed toward the improvement of the microphone. Gray died shortly after the company was formed, after which Mundy was assisted by Mr. Horace B. Gale, who for a time was the company's chief engineer. Later, Mr. Frederick M. Durkee became his associate. The microphone was improved by enclosing it in a metal case faced with a thick diaphragm which carried a "button." The microphone, the button, the telephone receivers, and batteries were connected by a series circuit. The diaphragm of the submerged microphone, agitated by incoming sound waves, varied the resistance of the button which, in turn, varied the current flow in the circuit and caused the telephone receivers to vibrate. The device worked satisfactorily in laboratory tests, but when installed in a vessel for practical tests the noises created by the ship's machinery had more effect upon the microphone than the distantly generated sound waves set up by a submarine bell.14
    By continued experiments it was discovered that, when the microphone was suspended in a water-filled tank secured to the inside of the hull of a ship, the outside sound waves passed through the metal hull into the tank while the ship-generated noises remained within the hull. This made underwater signaling possible. Moreover, it was ascertained that, with tanks located inside the hull on each bow, a ship could be maneuvered to a course on a line of bearing of the sound waves emitted by the submarine bell by simply equalizing the intensity of the signals set up by the two microphones.15
    A somewhat crude but practicable navigational aid had this been developed, but curiously enough there existed no market. Shipowners were unwilling to install the microphones unless submarine bells were installed. The Lighthouse Board was unwilling to install the bells unless ships were equipped to utilize them.16
    To demonstrate the practicability of the system, the Submarine Signal Co., with the consent and cooperation of the Lighthouse Board, installed and manned steam-operated bells on Pollack Rip, Hen and Chickens, Nantucket Shoals and Boston Lightships. Mr. Henry Whitney, then president of the company, controlled the Metropolitan Line, which operated four vessels between New York and Boston. These were equipped with listening devices. During this period of demonstration, improvements were made to the submarine bell and to the listening circuit. The rims of the bells were increased in thickness to provide a fundamental frequency of 1,215 vibrations per second. This increased the range of the aid to approximately 10 miles. The bells could be suspended from lightships, buoys, or by tripods placed on the sea bottom. They could be operated either by steam, compressed air, electric motor, wave motion, or hydraulically. To facilitate use, the telephone receivers were located on the bridge where a switching arrangement was installed to permit the operator to listen alternately to each of the two microphones.17
    Following these improvements and successful demonstrations, the navigational authorities of the United States and numerous other countries installed the submarine bells at dangerous points of navigation, and the Navy and numerous shipowners quickly installed the receiving circuits. By 1912 there were bells along the coasts of the United States, Canada, the British Isles, France, Portugal, Italy, Brazil, Chile, and China.18


Prior to 1912 little thought had been given to the possible use of the system for echo ranging, but endeavors had been made, with Navy cooperation, to develop it into a system of communications for submarines. Many attempts were made to adapt the bell to such usage. But it would not emit sound waves when installed in the flooding tanks of the submarine. Finally, it was discovered that by inverting it above deck it would function properly. However, in this location the compressed air which operated it could not be discharged into the hull because the pressure would be raised too high for human comfort and it was undesirable to vent it to the sea as bubbles would disclose a submarine's position. Moreover, it was difficult to use a telegraphic code with this type of transmitter. In attempting to solve the latter problem many transmitting devices, such as William's water siren, Wood's rotary field electric sounder, and William's longitudinal rod sounder, were experimented with, but with little success.19


In 1912 disagreements arose between Prof. R. A. Fessenden,20 chief engineer of the National Electric Signaling Co., and Walker and Givens, its owners, and the former's connection with that company was severed. He then joined the staff of the Submarine Signal Co. In 1914 he succeeded in perfecting an underwater sound oscillator that served both as the transmitter and as the receiver. This device, which emitted undamped waves and could be keyed, revolutionized the use of underwater sound and materially increased the range. The oscillator, weighing about 1,200 pounds, was contained in a watertight case that could be inserted within and fastened to the hull so that the diaphragm was exposed to the sea.21
    In signaling in code with this device, it was noted that reflected waves interfered with the reception of the signals. At the time it was not generally realized that these reflected waves could be utilized for ranging purposes. Fessenden believed that they could be used in measuring the distance between the oscillator and the reflecting object and obtained a patent upon such a method. Following the Titanic disaster the Government encouraged the development of all ideas which might enhance safety of life at sea. Fessenden's idea was tested with the cooperation of the U.S. Treasury Department which provided the Coast Guard Cutter Miami for experiments conducted on the Grand Banks. The tests gave strong indications that a feasible system could be developed, provided the range could be greatly increased.22


In 1916 Adm. A. G. Winterhalter, USN, in the U.S.S. Washington, conducted experiments in ranging, using sound in both air and underwater as well as radio. While the Nantucket Shoals Lightship made simultaneous transmissions of all three types of waves, Winterhalter steamed on various courses and plotted his positions by visual means and by air- and water-transmitted signals against those of radio signals. This was the first attempt to determine distance by acoustics and was the forerunner of one method of conducting hydrographic surveys.23
    It is of interest to note that on the first leg, on a heading which carried the ship away from the lightship, the whistle signal was lost in 2 minutes 10 seconds at six-tenths of a mile, while the submarine bell continued to be heard for 8½ minutes for an approximate distance of 2 miles. On the second leg, while headed slightly to the southward of the lightship, the submarine signal was picked up when the ship was distant approximately 7 miles and continued to be heard until the ship had passed and had the lightship on her port quarter, at a distance at over 5 miles. On this leg, the whistle was not picked up until almost 15 minutes after the submarine signal at a position when the ship was distant about 3 miles from the lightship and was retained for a distance along the track of approximately 2 miles longer than the bell. When the course was changed to the third and last leg, which placed the lightship fairly sharp on the port bow of the Washington, the bell and whistle signals were immediately picked up when the ship completed the course change at a distance of about 8½ miles.24
    This presents a vivid account of the vagaries of sound transmissions in air, and shows that the submarine sound was more reliable at longer ranges when the ship was headed toward the direction of the emanated waves. More important, it shows that the Navy was conscious of the possibility of submarine sound ranging at a comparatively early date.


As previously stated, the Navy installed Submarine Signal Co. underwater sound receivers for navigational purposes. In 1913, in an endeavor to complement flag signaling and to avoid the undesirable use of radio, sound transmitters were installed in one division of battleships for experimental underwater sound communications. With the division at anchor in Narragansett Bay, off Newport, R.I., perfect signaling was conducted by this method. However, it was slow because of the cumbersome signaling key utilized. The keying also created an annoying noise throughout the ship that could not be eliminated and was the cause of considerable discomfort to the crew. When underway, the churning of the propellers and the noises generated within the ships interfered to such an extent that further tests were abandoned for surface vessels. Our submariners, learning of the experiments, demanded installations for both detection and for communications between submarines, and the idea was kept sufficiently alive to keep it from becoming a forgotten method.25


When Germany commenced her unrestricted submarine campaign during World War I, it became obvious that we might be drawn into the conflict. To strengthen our preparations, Secretary of the Navy Josephus Daniels in October 1915 established the Naval Consulting Board headed by Mr. Thomas Alva Edison and consisting of the foremost scientists of the Nation.26 On 10 February 1917 the Consulting Board established a Special Problems Committee with a Subcommittee on Submarine Detection by Sound.27
    On 17 February 1917, Mr. R. J. W. Fay, second vice president of the Submarine Signal Co., appeared before the Naval Consulting Board, at its request, to discuss submarine signaling and detection. On 23 February members of the Special Problems Committee visited the Submarine Signal Co. plant at Boston, Mass., and witnessed a demonstration of the devices manufactured by that company. On 28 February, Fay wrote Mr. Lawrence Addicks of the Board a letter in which he enumerated the problems confronting the development of a system for the detection of submarines, stated the intense desire of the officials of the company to cooperate, and informed him that these officials had authorized him to obtain a test station at some suitable seashore location, preferably near Boston, and to detail personnel skilled in the art to work exclusively on the project. This letter was enthusiastically received and on 30 March 1917 it was gratefully acknowledged by the Secretary of the Navy.28
    At this time Fay proposed to Rear Adm. R. E. Griffin, USN, Chief of the Bureau of Steam Engineering, that he invite the General Electric Co. and the Western Electric Co. to participate in the experiments. With Griffin's concurrence, he personally discussed the matter with Mr. Owen D Young, of the General Electric Co., and Mr. Henry B. Thayer, of the American Telephone & Telegraph Co., of which the Western Electric Co. is a subsidiary, and obtained their agreement to work with the Submarine Signal Co. and to respect that company's pioneer interests in submarine signaling upon the conclusion of the emergency.29 The Western Electric Co. had been working previously on the general subject of submarine detection with the Coast Artillery Corps, U.S. Army, in the vicinity of Fortress Monroe, Va. As a part of that work, this company had planned a fundamental study of the disturbances given off by submarines and an analysis of other disturbances of a similar nature which might be encountered.30
    When war was declared on 6 April 1917, the experimental station had been established at Nahant, Mass., and was staffed by personnel of the three companies. The initial problem of the Nahant experimenters was to conduct the study which had been planned by the Western Electric Co. and to ascertain the distances these submarine disturbances could be heard.31
    During the early days of the war several destroyers were equipped with Submarine Signal Co. underwater sound signaling equipment. Since this was the only equipment available at that time which possessed possibilities of submarine detection, it was proposed that it be utilized. Later, Fessenden developed improved methods and devices which were fitted into the U.S.S. Aylwin and U.S.S. Calhoun. These destroyers were immediately sent to the war zone to conduct service tests and the equipments provided fair but insufficient detection.32
    Meanwhile, the Submarine Signaling Co. developed an extremely sensitive microphone which, when hung in the water, would receive distant noises as strong as they could be received by the Fessenden oscillator even when amplified by a vacuum tube amplifier. The only difficulty was that it was even more sensitive to nearby sounds. It was found necessary to suspend the microphone to a float attached to the ship by about 200 feet of cable. This eliminated noises generated on board ship and by water lapping against the ship's hull. By shutting down the ship's machinery and drifting, it was possible to detect noises generated at considerable distances from the listening vessel. This became known as the drifter set.33
    In May 1917 the Bureau of Steam Engineering assembled a group of scientists in Washington to consider a number of proposals involving magnetic detection. The members of this group were proposed by Dr. R. A. Millikan, Chairman of the Anti-Submarine Committee of the National Research Council, and consisted of Profs. Ernest Meritt, Cornell University; A. C. Lunn, University of Chicago; H. A. Bumstead, Yale University; Dr. L. A. Bauer, Carnegie Institution; and Mr. W. H. Nichols, of the Western Electric Co. The Committee submitted nine possible methods, several possessing sufficient potential to warrant development. However, they rendered the unanimous opinion that magnetic detection was limited in range. As a result of this opinion, it was decided that other methods must be also attempted.34
    On 8 May 1917, Secretary of the Navy Daniels held a conference in Washington on the subject of submarine detection attended by representatives of the General Electric Co., the Western Electric Co., and the Submarine Signal Co. Following this conference the Secretary, on 11 May, created the Special Board on Antisubmarine Devices. This was composed of Rear Adm. A. W. Grant, USN, and Comdrs. C. S. McDowell and M. A. Libbey, USN, and "was appointed for the purpose of procuring either through original research, experiment, and manufacture, or through the development of ideas and devices submitted by inventors at large, suitable apparatus for both offensive and defensive operations against submarines." Dr. Millikan, of the National Research Council; Dr. W. R. Whitney, of the General Electric Co.; Dr. F. B. Jewett, of the Western Electric Co.; and Mr. Fay, of the Submarine Signal Co., were appointed as advisory members. The Board was directed to cooperate with the above-mentioned companies and with all others whose experience and facilities might prove especially beneficial in solving the problem. The organization meeting was held in Boston, Mass., in June 1917, and at that time plans were drawn up to provide coordination of all activities engaged in the project.35
    On 1 June 1917, the National Research Council convened a meeting of scientific representatives of England and France, personnel of the Navy Department and of the three above-mentioned companies, and of professors and other individuals who had evinced interest in the subject of submarine detection. The foreign representatives explained developments abroad and suggested problems which might be investigated in this country for the improvement of their devices. Sir Ernest Rutherford described the results that he and other British experimenters had obtained with a binaural system, but stated that they had failed to develop satisfactory directional devices. The experiments of Professor Langevin of France in producing intense underwater sounds, using a technique developed by Pierre Curie, were discussed. This involved passing an alternating current of approximately 15 kc. through a quartz crystal, causing it to vibrate and propagate sound waves. Langevin used alternate slabs of quartz and steel plates for his underwater transmitter which emitted sound waves in a narrow beam. The Watzer apparatus, as developed in France, was also described. This apparatus stimulated certain original ideas which later led to the development of one of our best acoustical devices.36
    Following this meeting, the National Research Council recommended that certain scientists be brought together to work on the problems that had been generated. Acting upon this suggestion, the following additional groups were formed:
The New York group, under the direction of Prof. M. I. Pupin, of Columbia University, was assigned work in supersonics. This group conducted its studies at New York, Key West, Fla., and New London, Conn.;
    The San Pedro group, under Mr. Harris J. Ryan, was also assigned work in supersonics and similar lines of research;
    The New London group under the chairmanship of Dr. A. A. Michelson and the vice chairmanship of Professor Merritt, was assigned work on binaural devices. Other leading members of this group were Prof. H. A. Bumstead, of Yale University; M. Mason, of the University of Wisconsin; G. W. Pierce, of Harvard University; and Harvey C. Hayes, of Swarthmore College; and
    The Chicago and Wisconsin groups, which were assigned various problems in support of the other groups.37
    Independent work by numerous individuals was conducted in magnetic detection under the supervision of Maj. R. D. Mershon and in light detection under the supervision of Dr. H. E. Ives.38


The Special Board provided the necessary liaison between these scattered activities in order to eliminate undesirable duplication of effort. It acted as a clearinghouse for all information concerning submarine detection so that all concerned had available a complete record of accomplishments. When alternate lines of development appeared promising, the Board allocated the various phases to the several groups and individual investigators, and established schedules in order that parallel progress was maintained in all phases. It was necessary that the Board schedule and witness all tests and then make recommendations as to the suitability of the various developments. Once a device was recommended, it was necessary for them to cooperate with the various companies to assure that the device was properly engineered for quantity production and, afterward, to insure that production was scheduled to meet the needs of the Navy and our Allies.39 Figure 26-1
    In compliance with the directive, many of the country's manufacturing companies were invited to cooperate. In addition of the General Electric Co., the Western Electric Co., and the Submarine Signal Co., the following firms gave wholehearted assistance in providing urgently needed apparatus or material: United Wire & Supply Co. of Providence; Westinghouse Electric & Manufacturing Co.; Victor Talking Machine Co.; Locomobile Co. of America; Ford Motor Co.; Willys Overland Co.; Standard Parts Co. of Cleveland; Bryant Electric Co.; Worcester Polytechnic Shops; and Pittsfield Machine & Tool Co.40
    During the summer of 1917, such rapid progress was made on the solutions of the various problems and in development of devices that it became necessary for the Board to procure the services of several of the country's leading physicists and engineers as consultants. The need for added testing and shop facilities resulted in the augmentation of the New London group and its redesignation as the Naval Experimental Station.41
    This station was established at New London, Conn., in September, in an abandoned shop adjacent to the Fort Trumbull Military Reservation. The building housed a completely equipped machine shop initially operated by six enlisted personnel. Shortly thereafter additional buildings were completed to accommodate the ever-increasing personnel and to provide offices and laboratories for the scientists. A nearby marine railway was rebuilt to haul out the vessels to facilitate the installation of equipments for the numerous tests. Mr. S. W. Farnsworth, an experimental engineer of the Westinghouse Electric & Manufacturing Co., was graciously loaned by that firm to organize the station and get it in operation. His services were invaluable. By the end of the year its complement was 200 persons.42
    Continued increase in the work of the Board resulted in constant expansion of the station. New buildings were erected and civilian experts from all parts of the country were called in to assist in designing and engineering the several devices. A separate department was formed to relieve the research and development scientists of the functions of service testing and comparing the merits of the devices submitted. Extensive facilities for the required tests were provided by augmenting the previously assigned three converted steam yachts with the destroyer U.S.S. Jouett and three submarine chasers. As required, the submarine base at New London provided submarines as target vessels. Installations of practically every type of detector developed were made on the Jouett, and valuable information was obtaining concerning the applications of these for services usage. By the time the armistice was declared the station had expanded to provide facilities for a complement of 700 person.43
    In January 1918, Capt. J. T. Tompkins, USN, Office of the Chief of Naval Operations; Capt. A. J. Hepburn, USN, in command of the base at New London, Conn.; and Comdr. E. C. S. Parker, USN, in charge of the tactical group at New London, were appointed as additional members of the Special Board. Tompkins provided liaison between the Navy Department and the Board; Hepburn took charge of equipping submarine chasers and training their listening crews; while Parker cooperated, through the tactical group, in developing the tactics and methods of operation of the submarine chasers. In May 1918, Parker was succeeded by Capt. W. P. Cronan, USN. In July 1918, Hepburn was assigned to command the Queenstown, Ireland, group of submarine chasers. He was relieved as a board member by Capt. W. T. Tarrant, USN. In September 1918, McDowell was ordered to London and was relieved as member and secretary by Capt. J. R. Defrees, USN.44
    In order to provide still closer cooperation between the Navy Department and the Board, the following officers were named as additional members in May 1918: Lt. Comdr. G. K. Calhoun (Math), USN, Bureau of Steam Engineering; Lt. Comdr. P. S. Wilkinson, Jr., USN, Bureau of Ordnance; and Lt. Comdr. H. R. Bogusch, USN, Bureau of Construction and Repair.45


Numerous sound-interception devices were developed during the war and many of these were engineered for quantity production. The most important of these were the C-tube, an acoustical device developed by the Nahant group, and the MV-tube, an electrical system developed by the New London group.
    As originally developed, the C-tube was an aural device consisting of two rubber spheres, inches in diameter, mounted 5 feet apart on the ends of an inverted T-shaped hollow pipe that terminated in a stethoscope. The device was hung over the side or protruded through the bottom. The vertical shaft of the T was fitted with a wheel by which the whole assembly could be rotated until the sound seemed directly in front of the listener who then read the relative bearing, normal to the line of the two spheres, from an affixed scale. It was necessary to stop and quiet the searching ship before outside sounds could be heard since the rubber spheres were not exceedingly sensitive, and the apparatus suffered the same handicaps of other detection devices close to the ship. Later, the C-tube device was enlarged to provide six or more spheres on each of the inverted ends of the T.46
    Following the development of the C-tube, the Nahant group endeavored to embody the binaural principle into the drifter set. The problem involved was to devise a means by which the sounds from the several receivers would arrive at the listener's ears simultaneously. It was solved by the development of a "compensatory," a device for indicating the angle of incidence of a sound wave relative to a baseline containing two or more receivers. This was designated the K-tube Set. It consisted of three microphones arranged in an equilateral triangle, any two of which could be used simultaneously. Electric cables connected the microphones to two telephone receivers located at the listening station within the ship, one being the left, and the other being the right receiver. The telephone receivers were coupled to the operator's ears by the flexible air lines which could be varied in length by a wheel and the amount of this variation was transferred to a dial calibrated in degrees. Just as the bilateral radio direction finder did not indicate whether the bearing or its reciprocal was correct, it was necessary to pair the third microphone with either of the two previously used to determine the sense.47
    The K-tube set was used quite extensively during the war, but it was of little value other than for initially locating submarines since it could not be used for continuously hunting them down and destroying them. In an effort to develop this set for such expanded use, the company designed three types of towed devices designated OS, OK, and OV. These operated in exactly the same way as the K-tube set, but were designed to be towed at high speeds without introducing noises created by water motion. The float supporting the microphone was designed to maintain its submerged depth at all speeds and to maintain its microphone base line relative to the towing ship at all times. These developments were primarily the work of Drs. Irving Langmuir and W. D. Coolidge and Mr. C. E. Eveleth.48
    The MV-tube set was proposed by Mason on 3 July 1917. It was based upon original ideas conceived by him after hearing the descriptions of the Langevin and Watzer devices. As finally developed, it was an electrical sonic system of carbon button-type microphones, contained in a blister on each bow, which fed the sounds through phased circuits to a compensator which gave the direction of the received sound within a few degrees. This was the first listening apparatus which, when located within the hull of a ship, permitted the reception of sound waves emitted from a source a fair distance away. Its development eliminated, to a large extent, the necessity of using towed devices. Nonresonant receivers were used because they possessed the advantage of lack of sensitiveness to other than the natural frequency of the receiver diaphragm, a desirable factor since submarines emit sounds covering the entire audible frequency range. Moreover, they can be used binaurally, because they reproduce phase with fidelity.49
    Despite the large amount of research conducted on acoustical detecting devices, it was well realized that the ultimate equipment would have to be mounted entirely within the hulls of vessels equipped for submarine hunter-killer operations and yet not be subjected to ship-generated noises. Work on this problem carried on at the Boston factory of the Submarine Signal Co. aided in the ultimate development of the multispot system. Just prior to the termination of hostilities, two destroyers were equipped with a device that included four Fessenden oscillators located in the forepeak tank. Screens were placed between these oscillators so that each responded to sound waves coming from a single quadrant. Two adjacent oscillators were listened to at one time, and the operator determined the direction from which the sound emanated by relative signal intensities.50
    The problem of detection of submarines at rest was studied by a number of individual investigators and by several of the groups. Professor Merritt was working on the problem at New London at the time the Special Board was created, and he continued to follow the progress of the several schemes attempted until the close of the war. By midsummer of 1918, he had developed a short-range device designated the AD-tube. Dr. Vannevar Bush developed a device for this purpose, known as the audio telegraph, and, although it was engineered for quantity production, it was never put into general use. The Chief Engineer of the Westinghouse Electric & Manufacturing Co., Mr. B. G. Lamme, undertook similar investigations prior to our entry into the war and developed an apparatus which was undergoing service tests at the end of the war.51
    Detection devices such as the "electric eel," which consisted of several microphones encased in a long rubber tube, and the OK-tube, were developed for lowering from dirigibles and towing underwater. The PB-tube was developed for use by seaplanes drifting upon water. This consisted of three microphone units suspended separately from three rings on the plane's bow in such a manner as to form a triangle. The "electric eel" was also used for this purpose. All of these devices were used with compensators.52
    The Western Electric Co., in cooperation with officers of the Special Board, developed two separate methods of harbor-entrance submarine detection. One method consisted of 20 microphones, each supported on a tripod, connected by a single cable. Any one of these could be utilized by means of a selective switching system. Since only one could be utilized at a time the system was nondirectional and the submarine's location could only be determined approximately by its nearness to a particular microphone. Later, the binaural principle was adopted, each tripod being equipped with three microphones. An electric compensator and an audiofrequency amplifier were located at the listening post on shore. The submarine cable used in this installation was especially designed to maintain both circuits of the binaural system equal in electrical characteristics. Installations had been completed and were in operation at the entrances of Long Island Sound and the Chesapeake Bay when the armistice was declared. Equipment had been ordered for additional installations along the Atlantic coast. One complete system was provided the British and was being installed at the time of the armistice.
    The second method consisted of a system of magnetic loops, the forms of which varied with the contour and configuration of the areas where laid. These loops were connected to galvanometers on shore which indicated the passage of a submarine over each loop. The exact position of the submarine was determined by the sequence of the deflections received from the different leads. The loops were of short range and, therefore, confusion was not caused by a large number of vessels in the vicinity. Hence, this system served, as an adjunct to the first method. It had been installed and was in operation at the entrance to Chesapeake Bay prior to the termination of hostilities. Mr. E. H. Colpitts, noted electronic engineer of the Western Electric Co., was responsible for these developments.53


The successful use of early types of underwater detection equipment depended largely upon the skill of the operating personnel and the tactics employed by the antisubmarine vessels. Since these equipments provided only the direction of the sound source, determination of its location necessitated triangulation by vessels working in groups of three or more. As the devices were more accurate when the vessels were dead in the water, this decreased the effectiveness of the hunters. Further complications in attacking an unseen object with depth charges necessitated the entire group to use pattern firing at the enemy targets, which used all the evasive tactics at their command. Successful hunter-killer procedure involved ship handling, navigational plotting, instantaneous communications between the ships of a group, and coordinated attack. The submarine chasers were initially manned by untrained crews, and this provided the opportunity for training along the necessary specialized lines. The destroyers presented a more difficult problem. Their use in protecting convoys out-weighed all other considerations and time could not be devoted to the hunter-killer training. It was necessary to provide them with the equipment and let them work out their own doctrines and procedures.54
    The individual operators were trained at a school established at New London in September 1917. This school was equipped with the various types of equipment as they became available and was assigned vessels to provide the operators with actual seagoing experience using our own submarines as sound targets. Between the date of its establishment and the signing of the armistice the school trained over 1,500 operators. With the increasing number of installations, it became apparent that a number of officers would be required to supervise their installation and maintenance. A trial class of 50 officers was formed in July 1918 and favorable results were obtained from this training. In September 1918 the Hydrophone School was established at New London. During the months of its existence it trained approximately 150 additional officers.55


The purpose of the campaign against German submarines was to make the Atlantic safe for the transport of our military forces and the enormous logistic tonnage necessary for the prosecution of the war in Europe. While complete safety was not achieved, the devices developed did aid the Allied Forces in containing the menace. In some areas, especially along our coasts, German submarine operations ceased. The destruction of at least six submarines was credited to the use of American-developed antisubmarine equipment. Each submarine destroyed was the equivalent of an annual saving of 40,000 tons of shipping, representing a value of about $150 million. Thus, sinking of six submarines represented an annual saving of approximately $900 million as compared with the $2 million which was expended annually for research and development of the equipment. However, the major contribution of improved detection devices was the lowering of the morale of the German submariners.56
    Our own submarines universally welcomed the installation of sound-detection devices in their vessels. Such devices complemented the periscope when they were submerged, permitted them to detect and avoid collision with friendly craft, and aided in the detection of enemy ones.57
    Sound-detection devices were used extensively by convoy commanders to insure that the vessels being convoyed did not straggle or fall behind during darkness and also for the purpose of avoiding collisions during periods of poor visibility.58
    In retrospect, the underwater detection devices developed during World War I seem crude and inadequate compared with present-day sonar equipment. However, when one considers that extremely little had been accomplished before our entrance into the war, that only comparatively crude electronic amplifiers were available, and that during peacetime the normally accepted period between the conception of an idea and the installation of equipment is years, one must admire the endeavors, persistence, and accomplishments of the personnel engaged in improving these devices under the supervision and direction of the Chief of the Bureau of Steam Engineering.


Following the termination of hostilities all of these groups, excepting the Naval Experimental Station, were disestablished and only a few of the top scientists remained. These were headed by Hayes, who, before the war, had been professor of Physics at Swarthmore College where he had become interested in underwater sound and had conducted numerous experiments using the college swimming pool and the noises generated by trains traveling a railway adjacent to the campus.59 Because of his previous work and experience he had been chosen as one of the New London group scientists. His decision to continue in this field was most fortunate for the Navy because his efforts were primarily responsible for the development of the present-day sonar.
    Prior to the war, Fessenden demonstrated that soundings could be obtained with his apparatus in deep water, but it was incapable of measuring the small interval of time involved in shallow-depth measurements. His initial method was the transmission of nine dots, one-fifth of a second apart. Counting the number of dots which returned and allowing 80 fathoms per dot gave the approximately depth. If all nine dots were echoed, the depth was in excess of 640 fathoms. The wartime activity of the Submarine Signal Co. did not permit further immediate development of this system of depth measurement.60 Later, single pulses were resorted to, and the time from transmission to receipt of echo was measured by a stopwatch calibrated in fathoms.61


In late 1918 the transport U.S.S. Von Steuben was equipped with MV-tube apparatus. The war being at an end, it was decided to test this apparatus as an aid in the prevention of collisions at sea. In March 1919 the ship left New York with Hayes aboard to conduct the tests. Upon departure, the equipment worked perfectly, detecting and giving the positions of all ships near the transport. This good performance continued until the ship reached the Continental Shelf, at which time it apparently ceased to function. The equipment was thoroughly overhauled and checked, but it still did not work. A watch was maintained for the remainder of the Atlantic crossing with negative results, until early one morning when approaching the French coast the operator notified Hayes he was picking up the propeller noises of the Von Steuben but that they appeared to be coming from amidships instead of astern.62
    Hayes deduced that the failure to pick up the ship's noises during part of the passage was due to the fact the sounds were being directed down and reflected back from the bottom and that in the deeps the echoes were lost. This led him to experiment with the equipment as a depth-finding device. The equipment was mounted so that it could be trained to determine the angle at which reflected propeller noises arrived at the receiving apparatus. The angle determined, a simple trigonometric formula was applied, thus providing the depth. On the return voyage the Von Steuben approached Long Island in a dense fog, taking soundings with this instrument and setting courses conforming to the obtained soundings as compared to those of the chart, and made a perfect landfall on Ambrose Light. Later the apparatus was improved by utilizing a Fessenden submarine oscillator which provided a stronger and more readily identifiable signal and by calibrating the indicating scale in fathoms.63
    Following Hayes' return from the Von Steuben voyage, the Naval Experimental Laboratory was moved to Annapolis, Md., and consolidated with the Naval Engineering Experimental Station. There Hayes and his assistants began work to improve the sonic depth finder. With the Fessenden oscillator and the MV hydrophones he had all that was necessary for a sonic depth finder except an accurate timing device. By early 1922 he succeeded in developing such a device.64
    Meanwhile, several tests were made using Hayes' angle-of-reflection method. In January 1920 the U.S.S. Breckinridge ran a comparative line of soundings from Charleston, S.C., to Key West, Fla., using both this method and the dipsey lead, and it was determined that the sonic equipment gave more accurate measurements. Another test by the U.S.S. Blakely in May 1920 produced similar results. Both these tests indicated that, in water deeper than 100 fathoms, the sonic depth finder readings using the angle-of-reflection method became unreliable because the reflection angle became too acute.65
    Following the development of the timing device, the equipment was installed in the radio experimental ship, U.S.S. Ohio, with the idea of ranging between two ships. One of the ships was to generate underwater sound and at the same instant transmit a radio signal in a manner similar to the 1911 U.S.S. Washington-Nantucket Shoals Lightship experiment. The other was to receive both signals and, by computations of time and speed of radio and underwater sound, determine the distance of the transmitting ship. A second ship was not made available; therefore it was decided to test the time-measuring device by reflecting the sound waves generated by the Ohio off the ocean floor. In February 1922 she departed New York for Annapolis Roads Md., to test the apparatus. This test proved that a workable deep-sea sonic depth finder had been developed. Soundings on known bottoms in excess of 1,700 fathoms were made and compared. On the approach to the Virginia Capes a heavy fog was encountered and the ship was safely navigated into the Chesapeake Bay on soundings.66
    At this time destroyer reliefs for the Asiatic Fleet were being readied and it was decided to equip one of these, the U.S.S. Stewart, with the apparatus for the purpose of making a continuous profile of the ocean floor from the United States, eastward through the Mediterranean, the Indian Ocean, and up the west coast of China. In June 1922 the Stewart departed Newport, R.I., with Hayes aboard to direct the use of the apparatus and to insure that it functioned properly. He left the ship at Gibraltar and, from thence on to Chefoo, China, the soundings were conducted by the ship's officers and crew. Continuous soundings of the ocean floor were made for somewhat over 6,500 miles. This was the beginning of increased work in oceanography, to which the Navy has contributed over one-half the data. The Navy's deepsea sonic depth finder was, like its sister, the earlier shallow-water depth finder, the direct byproduct of the submarine detection and ranging problem.67


During the war it was realized that the ranges could be improved if a higher frequency oscillator and receiver could be developed. Therefore, considerable research was conducted in supersonics. In 1918 it was suggested that the piezoelectric property of quartz crystal might be utilized to produce a supersonic oscillator. The Royal Navy began the development of such a device and constructed a laboratory model which utilized sandwich arrangements of quartz and steel. This was a rather crude device and, like the Submarine Signal Co. devices developed by the Nahant group, it had to be suspended in the water by hanging it over the side. Despite this, great increases in ranges were obtained. The termination of the war separated British and American exchange of research information on this subject. The British Navy adhered to the quartz-steel development which became known as ASDIC, the abbreviation for the Antisubmarine Detection Inventions Committee; and the U.S. Navy continued its endeavors to improve the Fessenden oscillator.68 Later, the Navy, in 1927, abandoned the oscillator and developed the transducer which69 consisted of a battery of ferronickel alloy tubes driving a steel plate by magnetostriction.70
    The underwater sound group was moved from Annapolis to the Naval Research Laboratory in 1923, where 20 scientists, working under the direction of Hayes, continued their endeavors to develop a supersonic echo-ranging system employing electronic amplification. Their ultimate success will be related in a later chapter.

    1 H. J. Fay, "The Submarine Signal Company" (Soundings, publication of the Submarine Signal Co., Boston, Mass.), November 1944, p. 4.
    2 Thomas H. Whitcroff, "Sonic Soundings as Developed by the U.S. Navy" (U.S. Naval Institute Proceedings, 1943), p. 216.
    3 Fay, op. cit., p. 6.
    4 Ibid.
    5 Ibid.
    6 Ibid., October 1944, p. 4.
    7 Ibid., November 1944, p. 4.
    8 Ibid., October 1945, p. 5.
    9 Ibid., p. 6.
    10 Ibid.
    11 Ibid.
    12 Ibid., November 1944, p.6.
    13 Ibid.
    14 Ibid., October 1944, p. 5.
    15 Ibid.
    16 Ibid.
    17 Ibid.
    18 Ibid., p. 6.
    19 Ibid.
    20 Pt. I, numerous citations (index).
    21 Fay, op. cit., December 1944, p.4.
    22 Ibid., February 1945, p. 4.
    23 Whitcroff, op. cit., p. 216-217.
    24 Ibid.
    25 S. C. Hooper, "How the Navy First Used Underwater Sound," Soundings, May 1945, p. 8.
    26 Report of the Secretary of the Navy, 1915, Washington, Government Printing Office, 1915, p. 45.
    27 Fay, op. cit., May 1945, p. 6.
    28 Ibid., pp. 6-7.
    29 Ibid., p. 7.
    30 "History of the Bureau of Engineering During the World War," Washington, Government Printing Office, 1922, p. 48.
    31 Ibid., p. 52.
    32 Ibid., pp. 52-53.
    33 Fay, op. cit., May 1945, p. 8.
    34 "History of the Bureau of Engineering During the World War," op. cit., p. 48-49.
    35 Ibid., p. 48.
    36 Ibid., pp. 50-51; "Sonar" (Navy Department press release, 6 Apr. 1946), p. 2.
    37 "History of the Bureau of Engineering During the World War," ibid., pp. 51 and 61.
    38 Ibid., p. 55.
    39 Ibid., pp. 60-61.
    40 Ibid., p. 68.
    41 Ibid., pp. 54-55.
    42 Ibid., p. 55.
    43 Ibid., p. 59.
    44 Ibid., pp. 58-59.
    45 Ibid.
    46 Fay, op. cit., July 1945, pp. 6-8; "Sonar," op. cit., p. 1-2.
    47 Ibid.
    48 "History of the Bureau of Engineering During the World War," op. cit., p. 61.
    49 "History of the Bureau of Engineering During the World War," op. cit., pp. 51, 59, 62-66; "Sonar," op. cit., p. 2.
    50 Fay, op. cit., July 1945, p. 8.
    51 "History of the Bureau of Engineering During the World War," op. cit., pp. 67-68.
    52 Ibid., p. 69.
    53 Ibid., pp. 69-71.
    54 Ibid., pp. 57-58.
    55 Ibid., pp. 54, 59.
    56 Ibid., pp. 72-73.
    57 Ibid.
    58 Ibid.
    59 Whitcroff, op. Cit., P. 217.
    60 Fay, op. cit., December 1945, p. 7.
    61 H. C. Bailey, "The Evolution of Deep Sea Sounding Methods" (Journal, American Society Naval Engineers, 1951) p. 357.
    62 Whitcroff, op. cit., pp. 217-218.
    63 Ibid., p. 218.
    64 Ibid., pp. 218-219.
    65 Ibid., p. 218.
    66 Ibid., p. 219.
    67 Ibid., pp. 222-232.
    68 Maurice Prendergast, "Sonar and Asdic" (U.S. Naval Institute Proceedings, August 1948), p. 1009.
    69 Monthly Radio and Sound Report, Bureau of Engineering, May-June 1927, p. 12.
    70 This type of transducer utilizes the Joule effect wherein the dimensions of ferromagnetic objects are changed when placed in a magnetic field. Definite and fixed frequencies, usually above audibility, may be generated by such a device.
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