[cdawzrd]

Actually, it should be trivial to defeat without MATLAB:

1. Take the recording of interest 2. Use any audio processing software to apply a 400Hz-4kHz bandpass filter. If you don't have audio processing software or a computer, you can play back the recording over a phone. 3. Play back the recording via cheap computer speakers (no subwoofer) or over a telephone, and re-record

Low-end speakers don't have much output below 100Hz, so the new thumbprint from location (2) will replace the old thumbprint. The harmonics of the old will still be there, but bandpassing starting at 400Hz will cut out the strongest ones and make recovery of the original thumbprint very difficult.