Over what frequency range can the microphone of smartphone receive the sound?
The best idea is to ignore what everyone says, and test it yourself.  Install an app like "SpectralPro Analyzer", and either generate some high frequency sounds using PC programming (easy) or download some high-frequency MP3's from web sites.

I've done all of the above on many different phones - I find that I get excellent results for a very long way off the top of my hearing range, at least as high as 21kHz (the limit for those apps).  The interesting thing about this is:
a) everyone who said PC speakers can't do 21kHz was wrong, and
b) everyone who said smartphone microphones can't pick up high frequencies was wrong too.

Bottom line - almost everyone who's never tried this stuff makes a guess.  Good intentions don't make their guessing relevant though :-(

Best of luck with your project!

Here's a Samsung Galaxy Note-1 recording a Macbook Pro signal which went from 9kHz to 21kHz:



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