Comment Student work, not an effective strategy (Score 1) 129
This assumes that the device with the microphone is sensitive to frequencies above the hearing range. Most devices have a low-pass filter for the purpose of avoiding any input above 1/2 the sample rate of the DAC, since these will create artifacts, aliasing, and distortion. Even in the case that current devices have left out the low-pass filter, it costs pennies to add.