Awesome little oscilloscope!
This is a delightful app that functions as an oscilloscope for audio frequencies. I used an audio frequency generator (Function Generator Pro) on one device and plugged it into my iPhone via an audio cable and was able to view sine, square and triangle waveforms as if I were using an actual physical oscilloscope. I also built an electronic circuit to generate a sine wave and fed it into my iPhone via a Scarlett audio interface and that also worked wonderfully, showing the sine wave and frequency! The iPhone has a high-pass filter that cuts off anything over 10KHz, but for my projects that frequency was plenty high enough. Running an audio app and Soundbeam on my iPhone simultaneously showed me the waveform and the FFT-style spectrum analysis—the audio came out the speaker and back in via the microphone. What a great and inexpensive way to help understand how sound waves work! Enhancement request: let me zoom in horizontally while in waveform mode, and display the time scale.