Acoustic homing torpedoes did not see action until 1943 with the Falke/T4 from Germany and the Mark 24 Mine from the USA. These torpedoes were passive in that they homed in on the loudest sound that already existed in the water.
I would like to know who first invented this concept and did physical research on it, that is, actually tried to build a working prototype.
From Wikipedia, I was able to glean a few small parcels of information:
The first passive acoustic torpedoes were developed independently and nearly simultaneously by the Allies and the Germans during World War II.
The concept of a torpedo which would "home" on its target had been studied by torpedo designers as far back as the first World War. While the concept was highly interesting, implementation had to await a better understanding of the physics of sound generation and transmission in the sea and the development of the technology from which such a torpedo could be designed and constructed. During W.W. II, German submarines were equipped with electrically driven acoustic homing torpedoes which had started development as far back as 1933.
The T4 was not an ordinary straight-running torpedo, however; it was the world's first acoustic homing torpedo. It ran at 20 kt (37 km/h) for 7500 m and was introduced in March 1943.
Early in 1933 Germany started development and testing of acoustic homing mechanisms for torpedoes.
So apparently this concept dates back to 1933. However, there isn't a single citation for any of this. I find that surprising. Wikipedia fails here, as those 3 relevant articles don't have a single citation for what I'm interested in.
There is a very interesting site called maritime.org that has a bit more:
Division 6 (Sub-Surface Warfare, headed by Dr. John T. Tate) was the group tasked with the torpedo research and development role. The division's first objective was "the most complete investigation possible of all the factors and phenomena involved in the accurate detection of submerged or partially submerged submarines and in anti-submarine devices."5 Through the systematic study of all phases of underwater acoustics, the ground work was laid to permit engineering development and deployment of the acoustic homing torpedo during World War II.
It didn't give a date, but from the previous paragraph I inferred it was from 1940. I googled the name John T. Tate and surprisingly, could not find him. There were two "John Tate"s I found, one a mathematician and one a physicist (yes, both found on Wikipedia), but I couldn't find mention of them working on torpedoes.
And then there's this:
In 1943, it became known in the technical community that the Germans were using a torpedo called the German Naval Acoustic Torpedo (GNAT) with terminal homing, a torpedo that guided itself to contact with the target by the noise generated by the ship's propellers (cavitation). German development of the GNAT had been known in the U.S. Intelligence community, and in 1940, the NDRC sponsored a project to develop an acoustic homing torpedo.
That's written very anachronistically. If GNAT had been known to the US intelligence community on or before 1940, then I think it's safe the say the Germans had been developing it for at least a year. If Wikipedia is trustworthy, it goes back to 1933.
So I'm here to post the question. Who "invented" it (conceived and developed it)?
Just a cautionary endnote: Submarine tech history, even the "new stuff" of WW2, can often be traced back to WW1. Classic example is the Snorkel:
An early submarine snorkel was designed by James Richardson, an Assistant Manager at Scotts Shipbuilding and Engineering Company, Greenock, Scotland as early as 1916, during World War I. Although the company received a British patent for the design, no further use was made of it—the British Admiralty did not accept it for use in their Royal Navy submarines.
That wiki paragraph actually has citations. The reason I bring it up here is because the snorkel is often attributed to the Dutch, because they apparently had two submarines using them in 1940, which were captured by the Germans. For example, you read this article on u-boat.net and it makes it sound like the Germans first discovered the snorkel concept in 1940 from the Dutch. For all I know, that may be true, but it can only be true if the Germans were unaware of the British patent from 1916. I think this is a prime example of how the history of these things can be tricky. I wouldn't be surprised if something similar was going on here with the acoustic torpedo.