noun
echo sounder
Technical term for a device that measures water depth by emitting sound pulses and timing their return. Used in marine surveying, navigation, and fishing.
この船には最新の音響測深儀が搭載されている。
This ship is equipped with the latest echo sounder.
音響測深儀を使って海底の地形を調べた。
We surveyed the seafloor topography using an echo sounder.
ソナー is a broader term for sound navigation and ranging, often used for detecting objects underwater, while 音響測深儀 specifically refers to depth-measuring echo sounders.
Compound of 音響 (sound, acoustics), 測深 (depth sounding), and 儀 (instrument). The term is a modern technical coinage.