Vice Admiral Henry T. Mayo, Commander, Atlantic Fleet, to All Vessels, Atlantic Fleet
UNITED STATES ATLANTIC FLEET
U. S. S. PENNSYLVANIA, Flagship
1 May 1918
From: Commander in Chief.
To: ATLANTIC FLEET.
Subject: Listening Devices—Use of for detecting the firing of torpedoes.
Reference: (a) OPERATIONS’ letter no. C-26-178 of 25 April 1918.
1. The above reference (a) is quoted herewith for information and compliance:
“1. The Special Board on Anti-Submarine Devices at New London has considered numerous experiments for detecting, by listening devices, the firing of torpedoes. From these tests it was ascertained that the sound made by a torpedo running in the water, after being fired, is a very distinctive one and easily recognized. In conducting these experiments, various types of listening devices were employed, and the results obtained were positive in all cases.
“2. The experiments referred to were restricted to short range work, the torpedoes being fired from submarines. The ranges employed were generally between 1000 and 2000 yards. In using devices which indicated the direction, the torpedo could be heard, and its direction obtained, about half a minute before its wake could be detected from the bridge of the observing vessel, notwithstanding the fact that the observers on the bridge were aware that the torpedo was about to be fired, and were looking for it.
“3. These experiments were carried out at short ranges as it was inferred that torpedoes fired from enemy submarines would be fired at close quarters, and the object was to ascertain the value to a ship of its listening equipment in avoiding a torpedo fired at it by an enemy submarine.
“4. It is desired that when torpedo practices are held by vessels of the fleet, a listener be stationed at the Submarine Signal Company’s apparatus for the purpose of obtaining information on this subject at varying ranges. It is believed that in long range work a listener on board a vessel would know that a torpedo had been fired, and its direction from the ship, a perceptible interval before the torpedo could reach its target, and quick use of this information might save the vessel from being torpedoed.
“5. In the experiments carried out with the Submarine Signal Company’s installation, it was found that a special tuned microphone, installed in the place of the microphones furnished, gave better results. The standard microphones, however, were quite satisfactory and could be used efficiently.
“6. The Submarine Signal Company is now developing a special head-set, so adapted that the listener can be stationed on the bridge in direct communication with the captain.
“7. As the majority of naval vessels and numerous other vessels now under the control of the Navy, and used as transports, cargo vessels, etc., are fitted with the Submarine Signal Company’s installation, it is directed that action be taken in regard to having a listener stationed at this apparatus at all times, when a vessel is in the war zone, to give the commanding officer warning when a torpedo is fired.
(Sig.) W. S. BENSON.”
H. T. MAYO