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Comment by buzzwords | Hacker News Reader

Interesting trial. But I'm sure there will be techniques to clean the noise out.

I'm wondering too. I had a glimpse at a paper and it seems it works because even though ultrasound is "inaudible to humans, still leaks into the recorded speech due to non-linear amplification of the microphone’s circuit". The chart thought shows the leakage has small dB (-20) in audible spectrum.

Too bad researches didn't leave any samples of recording in the repo. Curious how it would be effective after: 1) filtering frequencies to 0-16kHz 2) getting 1-2sec sample duration of noise profile while nobody speaks and using noise reduction filter from audacity

Download the audio from the YouTube video at the top of the page - it has a sample in it

The idea is that the analogue components are saturated already so there's no available margin for the lower frequencies to further actuate the diaphragm or amplifier.

lots of circuits will fold higher frequencies down into lower frequencies (but at lower energy).

If you can generate enough energy, you can push enough energy into other circuits that they saturate (reach the end of their working range) and will output noise.

Non-linear circuits l̶o̶t̶s̶ ̶o̶f̶ ̶c̶i̶r̶c̶u̶i̶t̶s will fold higher frequencies down into lower frequencies

Pretty much most circuits are non-linear, for real-world circuits "linear" just means "linear within normal operating range"

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