Although not named in this article, the person behind this installation was Earl C. Hanson. Also, the reference to the "low frequency" employed means this system this actually employed electrostatic induction rather than radio waves.
The Wireless Age, April, 1918, pages 590, 593:

Wireless  Music  For  Wounded  Soldiers

By  Albert  Marple
transmitter BEFORE a great while the boys of U. S. Army in France who are injured while doing their "bit," will be persuaded to forget their aches and pains along with all the hardships of war, by strains of music, carried to them by wireless. It is planned that they will hear novels and poetry and news stories, the soldier boy who is too ill even for a little entertainment not being disturbed, for the entertainment will be distributed in individual doses by wireless telephone and phonograph.
    Through the generosity of the Ebell Club of Los Angeles, the first set of this wireless phonograph has been purchased for $1,000; it is to be donated at an early date to the American Base Hospital in France. The outfit will consist of a transmitting set, along with fifty portable or hospital receiving sets, for use on fifty different beds. By placing one of these sets between two beds and equipping it with two receivers, each receiving set may be made to bring joy and relief to a pair of our wounded fighting men. The sets may be detached from any bed in a moment and carried for use to some other part of the room or building. patient listening
    As a rule the conditions of the various patients in a hospital prevent the playing of a phonograph. The music, while beneficial to some, would be very irritating to others. This difficulty is overcome by the wireless phonograph.
    The sending apparatus is located within a sound-tight room somewhere within the hospital and the attendant to operate the device has only to start the phonograph and throw a switch. From the phonograph the music travels by wire to the wireless telephone transmitter, from which it passes in the form of electrical waves to the sending aerial, going from this point out into space.
    The receiving apparatus consists of a light, sensitive telephone receiver which is connected by a silk cord to a metal or wooden case three inches wide, six inches long and four inches high. This case is connected by a tiny wire to the bed post or spring, which constitutes the receiving aerial. After being released by the sending aerial the sound waves travel through space until they are caught by the receiving capacity and transmitted from this by the tiny wire to the receiving cabinet, thence along the silk cord to the telephone receiver, which is held to the ear of the patient.
    Another feature of this device is that the phonograph may be disconnected and stories and newspapers be read to the patients over the wireless telephone.
    The transmitting apparatus connected to the phonograph and also to the telephone consists of a group of telephone transmitters arranged in a suitable casting. Being operated on low frequency the waves of this machine are not likely to interfere with or be troubled by the waves of high frequency systems. The system may be operated by a few dry cells, at a cost of not more than ten cents a day in connection with the largest hospital.