A question about sonar module experiment

BradtheRad said:

As I understand it, sonar broadcasts a pulse mechanically into the water. Then you listen for echoes.

You want to avoid traumatizing the fish with a strong pulse. I think it will be sufficient if you suspend a small earphone in the water. Avoid letting any more than a few volts contact the water. Or insulate the earphone from the water because tropical fish come from salt water.

The real challenge will be to detect echoes, phase differences, frequency response, etc., when a fish is in the tank as compared to no fish.

I think it will help if you use two microphones to get a stereo image. If you broadcast white noise and listen to it in stereo, I think you will detect the fish swimming, the same way a blind person can tell someone is walking by due to background noise being blocked.

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bianchi77 said:

thanks for the response,
do you have any links / reference about it ? circuit diagram ?
thanks

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BradtheRad said:

Sorry, I have no references, etc. Just a few things that came to mind.

In addition there's the concept about dolphins using sonar to detect things in the water and the sand. They can even 'see' inside living tissue.

They send out clicks which return to them (in stereo). Their brains contain neural networks which reconstruct an image of their surroundings based on acoustic information (whereas our imaging is visual). How they do it continues to astound researchers.

Your project sounds about the same category of undertaking.

Or maybe it will be like an underwater motion-detector? It will be an accomplishment if you can detect something the size of a fish.

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