A free program for Android, by keuwlsoft.

Pulse Echo Sonar Meter is an app that uses the microphone of your phone or tablet to detect the echo of a previously recorded audio pulse. This app is a fun and easy way to demonstrate acoustics principles, and it is handy for those who are learning or interested in acoustics.

It is very easy to use, and you can even use it as an educational tool for your students. The app records the audio pulse, and then the microphone detects the echo and creates an audio signal. The app then shows the results on a graph and map. 

It is also possible to visualize the results in a time-series waveform. The app has a settings option that allows you to change the settings, such as the volume and the frequency of the audio pulse.

It is very simple to use, so it is suitable for anyone who wants to learn more about acoustics and the microphone.