quickest way to read & write audio files with mic input? audio buffer?

Does anyone know what the shortest length an audio clip can be?

I want to have a particle system falling on two box colliders, and have one box trigger the audio clip, and one box trigger the recording of an audio clip. But is it possible to record the clip to a buffer and not as a file for faster load time? Whats the fastest way I can read and write a file. Hope this makes sense. Thanks!