Controlling the microphone on Android

I’d like to use the microphone to pick up an ultrasonic signal (above 20 Mhz) - 8-bit binary pulses - on both the iPhone and Android.  Is there a way to

  • adjust the input volume to maximum
  • adjust the low and high-pass filters to accept only 20-25 Mhz?  

Anyone know if the microphone cut-off filtering is in hardware or software?

Thanks All,

Derm