# Using water to amplify sound

It seems that water generally dampens sound waves. Is there any way one could attach a speaker to a body of water in such a way that the water would actually amplify some frequencies (for nearby listeners in the air, not under water)?

Imagine a speaker on a boat on a small creek. Listeners are on the bank.

Quite remarkably, one can amplify sound using the mechanical energy of a water jet, which was invented by a cousin of Alexander G. Bell, according to the book "Soap bubbles" by C.V. Boys available online, http://www.gutenberg.org/files/33370/33370-h/33370-h.htm, see pp. 113-115.

Sound carries over water really well. Speakers on a boat in a small creek will reach the bank more clearly and loudly than if sound traveled the same distance through say a grassy field..

• I think this actually has more to do with refraction bending the sound's path due to cooler air over the water. Dec 25 '13 at 3:21

By using a Resonance Tube. :)

This is obviously the laboratory version of the experiment, but with a large enough tube, it can be done in a lake, too!

Each frequency needs a different resonating length. You can even try this at home; buy a small speaker which emits a certain frequency tone, submerge a pipe into water - like in the picture - and slowly change the submerged length until you find one that gives a very loud sound, which can be heard clearly. This is resonance.
Here is a video that explains the concept well. :) (There's also an additional concept of how the speed of sound is measured by this technique, but it explains the basic concept well)

• This is mainly just resonance of the air column. But the question is about whether water has resonant frequencies. Feb 23 '14 at 10:38

Sound travels better in water than it does in air. Anyone who has listened to an outboard engine underwater will know that it is much louder underwater than above water. This corroborates the fact that sound travels better in moist air, on a cloudy damp day the train whistle that you hardly hear on on a su nny dry day sounds like it is right beside you. This means you listeners have to be under water. Good luck with that.