AudioUnit tone generator is giving me a chirp at the end of each tone generated

Question

I\'m creating a old school music emulator for the old GWBasic PLAY command. To that end I have a tone generator and a music player. Between each of the notes played

Answer 1

That little chirp is generally an artifact of mathematics. The ear essentially analyzes input signals in the frequency domain. A steady sine wave at frequency 220 Hz, for example, will sound like an A. However, when your sine wave is *un*steady, there are other frequencies that show up due to the boundary. In particular, you get a bit of a pop due to the very high frequency component of starting or stopping a sound abruptly.

The way I solved this in my synthesizer (in Javascript, not Obj-C, but the concept here is the same) is to fade the sound in over 300 samples or so on note on, and fade the sound out over 300 samples or so on note off. There's no way to truly eliminate boundary effects other than not having a boundary at all, but even a small and imperceptible amount of fade will render the boundary effect imperceptible as well.