There is an allegation that a particular aviation headset causes tinnitus.
It is one of a number of active noise reduction (ANR) headsets on the market.
An ANR headset uses basically a mike, a tiny speaker and some op-amps inside each earcup, and the speaker is driven so as to generate a zero SPL inside the earcup.
That would just give you noise reduction, and the audio would get cancelled too, so they feed the audio into the summing node of the op-amp, so you hear it OK.
So... all the components required for oscillation are in place!
And it's true that some of the cheaper ones do "whistle", or give out an audible hiss.
The headset in question (I have two - $1000 each) certainly doesn't whistle, to my hearing, so if it does it will be high up, and because some pilots are teenagers, it would have to be well above 20kHz otherwise there would be loads of complaints.
I can't see any possible route to ear damage other than a very high pitch oscillation, possibly confined to when there is an incoming audio.
So I would like to test for this.
I have a TEK digital scope which can do FFT, and have a Marconi 2024 spectrum analyser which goes from 10kHz to 2.4GHz :)
Can anyone suggest what sort of microphone would work well? I don't want to spend loads of money on it, say $100 max, and it needs to be easy to interface.
I was also going to get a ribbon tweeter (loads on Amazon for about $40) to test the frequency response of the mike with, using my HP3314A signal generator. But of course the tweeter won't be flat-output anyway. But then I am only testing for *any* component above what the headset is supposed to be emitting...
Any suggestions would be much appreciated.