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.