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I'd like to understand if non-linear mixing of human speech with a high-power ultrasonic "carrier" in air could produce sidebands with more power than the original speech.

30 kHz to 300 kHz has a wavelength range from about 10 down to 1 millimeter in air. This is still much longer than the mean free path, but air is not an extremely high-fidelity medium at high sound pressure levels, especially when the pressure gets anywhere near comparable to the static pressure.

The Wikipedia article Nonlinear acoustics gives several mathematical model for the propagation of a single wave taking into account the nonlinear response of air to sound with a "high amplitude to wavelength ratio", but what I'm trying to understand is how to estimate the power in the sideband produced in the acoustic analog of four-wave mixing.

If someone could even just help guide me through the excellent presentation Introductory Lecture on Nonlinear Acoustics by Vincent Tournat at CNRS so that I can calculate the sideband power, that would be great!

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