Underwater speakers

[Hero999]

A horn at one end of the pipe should do the job of impedance matching between water and air quite well.

Loudspeaker and headphone handbook - Google Books

Come to think of it, this must be easy look at how well a stethoscope matched the impedance between the body (mostly water) and air.

The human ears also match the impedance of the air to the liquid in the inner ear.

 

[BrownOut]

The Humpback whale can make sounds heard from miles away, so there must be a way...

Wish I took more interest in sonar when I was in the navy.

Make that thousands of miles! It is believed that a whale in the north Atlantic can communicate with his mate in the tropics.

 

[Sceadwian]

Hero, I think you have some very distorted impressions of how well a stethescope works. In contact with the human body it is only useful for very limited and low range of sounds. lots of dips and peaks, which doesn't matter because it's primarily for listening to low frequency sounds in the first place it can't pick up any high frequency sounds of any kind over any distance in the body. The human ear isn't even within the same realm of discussion, the internal structure of the inner ear and how outer ear interacts with it which allow it to function are incredibly complex, nothing simple at all about it, even the most sophisticated modern sound devices can barely keep up with the technology in the human ear.

There is a very big difference between a device which can produce some tones under water and an underwater speaker.

 

[Hero999]

it can't pick up any high frequency sounds of any kind over any distance in the body

How can they doctor listen to the chest so well then? Breathing is mostly high frequency noises.

 

[Mikebits]

Actually; here is a frequency response of a typical stethoscope.

**broken link removed**

I got the graph from the link below. Keep in mind these test were conducted on human subjects, I think much of the lack of high frequency response is due to the response of the body.
Acoustic Stethoscope Review Page 1, Best Stethoscope, Omron Sprague Rappaport, Littmann Cardiology III review, Stethoscope Review, Allheart, ADC Adscope, DRG Puretone, Littmann Cardiology, Master Classic II, Classic II SE,Omron, Prestige Sprague Rapp