Longer sound ranging

How far can a ping be heard by say an electrostatic mic?

If the ping went out concurrent with an IR led flash, the thing with the mic might see that, know the air temperature and calculate closely how far the flash/ping generator is away. On close to standard days sound may travel 343M/1056ft plus or minus some for warmer or colder air. Get it right and you can be within 2cm maybe less using Arduino.

It's not as neat as point at something and know but if your mic can hear the ping at 1000ft, you can measure land.

inverse square law and signal to noise

Mark

You have to shout pretty loud to be heard 1000 feet away.

…or use a cannon, like they did in the 17th cenruty

Could be a fairly neat solution for a follow-me luggage. Have the master use that for signal and the following device can calculate how far away it is.

300 meters is a bit much for just about any sound signal, unless you use highly sensitive and highly directional microphones on the other side, but even then... My bat detector is doing 50-100 meters according to the manufacturer, the lower end of that seems reasonable based on field experience, and bats produce really loud sounds (up to 140 dB).

Okay but that's still more than 4.5m a ping board will give.

Ultrasonic waves don't disperse as quickly as audible sound but I get it won't be as far as I'd like.
Still, the ping relies on echo, twice the range is not unreasonable and likely short of what's possible.

Caveats: wind, rain, other ultrasonic and IR devices.

I have seen ultrasound sensors that do 10 meters before.

A quick Google search turned up this instructable, claiming to reach almost 10 meters with a regular HC-SR04 (or about 19 meters one way).

Senix claims 21 meters - that would be about 42 meters for a one way distance measurement.

Actually I expect you get a bit more for one-way transmission as you don't have the energy loss of the reflection itself. Making the receiving microphone more directional will also help a lot, as it allows you to concentrate and amplify the incoming waves.

Nevertheless it's going to be a tall order. You're looking for about five times the distance of the Senix, so you get just 4% of the sound intensity (1/5[sup2[/sup]).