问题
Can the windows phone 7 in-built microphone detect frequencies higher than 18kHz?
回答1:
Technically yes, the API supports recording PCM with sufficient quality to express a 18kHz sine wave. Standard POTS lines and even T1 lines generally operate at 8 kHz 16 bit which is mathematically enough to correctly record a max of 4 kHz. And since the mic isn't usually used for anything higher quality than telephony audio, I bet the limiting factor will be the hardware... your mileage will definitely vary from phone to phone.
来源：https://stackoverflow.com/questions/6114573/can-windows-phone-7-microphone-detect-frequencies-in-the-range-of-18k-19khz