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Why Fish Don’t Have Ears

Bio-Acoustics 109

When sound waves come in contact with water, even at an angle perpendicular to the water surface, 99.9% of the sound intensity is reflected away and only 0.1% enters! Yelling at fish doesn't help much and it is hard to scare fish by talking.

Sound into a watery medium like our flesh (read ears) is not very good and special things must be done to magnify the sound.

We collect 1800 square mm of sound with our ears (LBJ did better) and send it to our 70 square mm ear drum and then to the 3.2 square mm of the stapes attachment to the ear drum. 1800/3.2 means a 563 fold improvement with yet another reduction in impedance of 30% due to the malleus, incus, and stapes levers for a grand total of 730 fold improvement.

Even if only 0.1% of the sound gets into our flesh we magnify it adequately to do the job.

Now fish are like the water and the sound well is transmitted in water with a rapid speed of sound and it blasts into the fish tissues will only small losses.

Why stick ears on your body when your whole body is like a microphone? For a nice treatment on sound in water and air see M. W. Denny, Air and Water: the Biology and Physics of Life's Media. In fact, if you have a bookshelf with about 1.33 linear inches of space left, this is the best book you can buy to fill it. Princeton University Press publishes it.

If you don't have the bucks to buy a copy, be the first one in your university library and check it out for the semester.

CED readers need to go back to the last issue of CED and credit Denny's outstanding book as I was lax and did not do my attribution job nearly well enough!



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