Listening stations served as an effective defensive measure, but throughout 1915, U-boats had turned to aggressive attacks on mercantile shipping. An equally aggressive antisubmarine policy became an Admiralty priority, and that priority was passed to Hawkcraig. Submarine hunting on the open seas required the ability to detect a U-boat as it transited toward the shipping lanes and certainly long before the predator could maneuver into a torpedo firing position. The vessels assigned to Ryan would now head beyond the Firth of Forth with this new mission.
British listener on board a trawler. He is rotating a directional hydrophone suspended from the end of the boom. (Courtesy Marist College; Lowell Thomas Archive)
Once again, Ryan began with a single, non-directional hydrophone. Although intended to provide mobility, the vessel, initially Tarlair, later joined by the drifter Couronne, had to stop while the hydrophone was lowered over the side. The vessel’s machinery would have masked any sounds coming from a distant target, and this early hydrophone was not designed to be towed far enough astern to eliminate the vessel’s own noise. The sophistication of these single hydrophone drifter systems would improve with time, but the practical-minded Ryan had an immediate need—detect the U-boat—and he would use what was available.
LISTENER TRAINING BECOMES A PRIORITY
But the concept of submarine detection depended on two things—the hydrophone and the listener’s ear. There were, however, uncertainties within the hydrophone service as to the quality of both. Lt. H. W. Wilson, RNVR, serving under Ryan, described, with a bit of naval irony, the medical exam given to those seeking membership in a service dependent on a sailor’s ears:
[I]t will not surprise you to hear that we were subjected to a rigorous medical examination on joining. All the organic equipment with which man is born into this world, including the vermiform appendix, was scrutinized and tested. Everything came under a punishing medical survey except only—the hearing!3
It would not be an easy job, that of the listener. The oceans resonated with the sounds of whales and other marine mammals, of the chatter from many species of fish and invertebrates, of storms that churn the ocean surface, and of waves crashing against the shore. But it was the ships, large and small, commercial and naval, that filled the depths of the oceans with sound. And then there was that new vessel—the submarine—whose characteristic sounds depended on whether it was patrolling on the surface with its diesel engines, or submerged and running on electric motors. Even the rotating propellers of ships and submarines created their own list of distinct rhythmic sounds. Ryan’s hydrophones were capable of “hearing” it all. It was a technology not well understood by those in the hydrophone service; yet with training, it became, according to Lt. Wilson, a trusted and valued tool:
All I can tell you is that a hydrophone is a piece of gear assuming various forms, containing a microphone,… [where] the flow of electrical current, results [in] the translation of the engine sounds of ships in the vicinity, and any other neighboring subaqueous tremors, such as the sighs of a lovesick mermaid. All this medley of sound is reproduced by telephone receivers connected by cable with the hydrophone, and the classification is left to the listener.4
Was it a submarine or a lovesick mermaid? With experience a listener could learn to distinguish many natural and man-made sounds. But it was the ability to classify specific sounds as being from a U-boat which would enable the hydrophone-equipped hunters to carry out an attack. Training was the key to success, and that became yet another mission for Ryan and his Hawkcraig staff. Candidates for the hydrophone service would learn to recognize the rhythmic sounds from a submarine’s rotating propellers and machinery.5 The “sighs of a lovesick mermaid” would be classified among the sounds not characteristically rhythmic, though why the poor girl shouldn’t sigh rhythmically I don’t know.
Thus, at Hawkcraig, “an organized system of training of officers and ratings was instituted, an instructional staff appointed, and lecture-halls, workshops, ad hoc genus mone [and that sort of thing], put up.”6 Ryan’s students had access to the Firth of Forth shore stations where vessels from the British 6th Battle Squadron (Admiral Beatty) at Rosyth provided opportunities to hear large and small surface vessels, essential for distinguishing them from a submarine. But … that required the student listeners to have heard what a submarine sounded like.
One of the British B-class submarines commissioned during the first decade of the twentieth century. Considered obsolete by the beginning of the war, they still performed important missions, including support of Captain Ryan’s experimental work in the Firth of Forth. (Library of Congress (LOC) LC-F81-2000)
Among the vessels provided for the ever-resourceful Ryan was the aging HM Submarine B-3, which, in 1916, had been outfitted at Leith, on the southern coast of the Firth of Forth, with one of Ryan’s experimental hydrophone systems. Throughout the remaining years of the war, B-3 was stationed at Rosyth for use by the training staff at Hawkcraig. Lieutenant Wilson, however, lamented the use of an inappropriate submarine for their listener training: “Why an obsolescent submarine of our own, and that, too, only occasionally? Why not a U-boat captured from the enemy, and run daily for our benefit?”7 These were questions for which Wilson had no answer. He was, however, certainly justified to ask them. During the summer of 1916, a captured German submarine in the hands of the French Ministry of Invention was being thoroughly investigated, and was found to have its own acoustic system.8
Because B-3 was not always available, “the actual movements of a submarine under water at varying distances from a hydrophone were recorded by a phonograph, and records made so that the sounds might be reproduced at will for the education of the ear.”9 Recordings of submarines and other underwater sounds became a common practice, both in Britain and eventually the United States, where the Victor Talking Machine Company in Camden, New Jersey, provided the phonograph recording technology.10
Listener training soon expanded beyond the Firth of Forth. Instructor teams were assembled and dispatched from Hawkcraig to listening stations and hydrophone schools that were being established in 1917 and operated throughout the war. “At Malta an experimental station, with a hydrophone training school, was started in the autumn of 1917, and good work was done both there and at a hydrophone station established southward of Otranto at about the same time, as well as a hydrophone training school started at Gallipoli at the end of the war.”11
The success of Ryan’s training program can be measured by the recognition of this effort by Britain’s Admiral John R. Jellicoe: “The greater part of this training took place at the establishment at Hawkcraig, near Rosyth, at which Captain Ryan, R.N., carried out so much exceedingly valuable work during the war…. I am not able to give exact figures of the number of officers and men who were instructed in hydrophone work either at Hawkcraig or at other stations by instructors sent from Hawkcraig, but the total was certainly upwards of 1,000 officers and 2,000 men.”12
Jellicoe was close. According to Lieutenant Wilson, based on his service under Captain Ryan at Hawkcraig, “1090 officers, including Base hydrophone officers, submarine officers, and Royal Marine submarine mining officers, and 2731 ratings had either attended Hawkcraig for courses, or had received instruction from Tarlair travelling parties.”13
While the successes of Commander Ryan and his Hawkcraig staff brought praise from the Admiralty, as far back as 1915 there had been growing interest in the need to incorporate science into the development of listening devices. Ryan had his first encounter with a scientist that summer when a retired professor, Alexander Crichton Mitchell, arrived at Granton Pier with an idea to detect submarines with a non-acoustic technology. Ryan, who was skeptical of the civilian scientist at first, soon found Mitchell’s ideas worthy