function sampleRate() {
  return main.audiocontext.sampleRate;
}
Returns a number representing the sample rate, in samples per second,
of all sound objects in this audio context. It is determined by the
sampling rate of your operating system's sound card, and it is not
currently possile to change.
It is often 44100, or twice the range of human hearing.

@method sampleRate
@return {Number} samplerate samples per second