You can test the audio devices connected to your smartphone.

- Stereo Test : You can test the left and right sound of a stereo audio device.

- Delay Test : You can test the audio delay. Check the time difference between when the white ball passes 0 milliseconds and when the tick sound actually sounds on the audio device. Usually, wireless connections such as Bluetooth have longer delay than wired connections.

- Frequency Test : You can test the frequency range of your audio device.
※CAUTION : Testing at high volumes can hurt your ears. Turn the volume down and do a frequency test.

I hope this app is useful to you.
Thank you.