Buzzers For Underwater Application

Same as in air. sound is vibration in both air and water. Just travels faster in water. Also more well insulated.

Google underwater buzzers and see what you get.

Sonitron's SP7 is one such buzzer.

Buzzers, speakers and so forth designed specifically for underwater service are far more efficient at coupling their acoustic energy to water than an equivalent in-air device does to air. This is because the acoustic-impedance mismatch between the vibrating surface and water is much less than in air; hence more the acoustic energy is coupled to the medium and so, for a given input power, an underwater acoustic device will sound louder. These devices are not the same as an in-air device rigged for underwater use because typically the latter still contain an air-gap which drastically decreases the coupling between the vibrating element and water. You can waterproof an in-air buzzer, but it will be much less efficient. These may still suitable for your application, but if loudness and/or great range is required, opt for a device designed for underwater service.

I agree with everything you say and cite except your explanation that the acoustic impedance is why acoustic energy is more readily transferred to water instead of air. This is a circular logic fallacy, like explaining that the reason why some people's feet are longer than a foot is because they measure to be more than twelve inches in length.

Getting back to why acoustic energy transfer is much better in water than air is largely because air, being a gas, is a compressible media. Water being a liquid is comparably non-compressible.

And the molecules are much closer to each other in water than in air. Even closer to each other in metals. Look at speed of sound through different materials.

You're right: the relative impedance is a measure of the coupling, not an explanation for the mechanism itelf.

Amazon's got everything....

http://www.amazon.com/s/?ie=UTF8&keywords=underwater+noise+maker&tag=googhydr-20&index=aps&hvadid=30937653981&hvpos=1o1&hvexid=&hvnetw=g&hvrand=9244250072346460443&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_9eds1fybia_b

What is the application?

The electronics are potted in resin, either epoxy or polyurethanebut today the housings are well water proofed with with rubber O rings which compress with a gland or by pressure. Just like a diving watch.

Please explain the perceived need for such a device.

To let you know it is tea break? To let you know you are being stalked by something that is going to eat you? Or to awake you from that comfy seabed! I also wondered why one would need an sea proof buzzer. Speaker, microphones I understand. Also curious!

A buzzer is easier to activate automatically than speaker/mic. They can be used for a variety of operations ranging from getting the attention of a diver, to scaring off unwanted species.

Quite. It would be of immediate interest to know whether the original poster's application correlates with any of these.

Hello PWSlack and Lyn... good that you both struck the right note....

the application is... wearable micro sized alarm for women. The challenge is to completely enclose the circuit (to avoid shorting of circuit due to rain water... or while bathing (if they still wear while bathing :( . If i enclose it fully... it leaves no option for producing sound,So i just happen to stumble upon the challenge of making the buzzer water proof... so it led me to think of similar situations where it is solved already.

Water-resistant is not the same as 'Underwater Application'. This "wearable micro sized alarm for women." is very unlikely to be operated under water.

You see, this is the reason for members asking for some general idea about what is going on. Sound pressure in air is completely different than sound pressure in water.

How far away is this alarm desired to be heard? Is this measured with a microphone or a hydrophone? Inside a nearly vacant office building? Busy shopping mall? Women's shower at the 'Y'?

as per spec of a buzzer, i love it to be minimum 75 dB measured at 10 cm away from the buzzer.... does not matter whatever the ambience

12 replies before we got some information!

Agreed, it's a head shaker.

And some of the info is extraneous. What difference does it make that it is intended to be used by women? Will it not work on children?

Or, is it intended to warn men that a woman is nearby?

centuries of arguments gone by to decide which pronoun to use ....he or she.... so not sure... so ended up with a soft corner for xx

Some interesting scenarios

watch youtube.... i am just thinking how a speaker work in this case???

Appreciate any thoughts???

https://www.youtube.com/watch?v=E9J611BuXhw