Occasionally I receive a question about how ASW equipment was tested.
Here's one example, from a folio of Submarine Signal Company's work, that shows how they tested the "rats" (microphones) and frames for the K-Tube hydrophones that we've been looking at in recent issues.
Photo caption: Test Tank for Sound. This was the first tank built for experimental and test purposes at Lynn. It was lined with a foot of coke on all sides and the bottom. Artificial sound was introduced into the water at one end through a C-Tube and the rats were matched and the triangles tested in reference to this sound.
Enjoy the fall,
—Todd Woofenden, editor