Hector Martin

(5) Ok I just read it. H sentences quoted from me were not, I am certain, following on from one another in the way it has been edited. So when I talk about permanent or temporary hearing loss, that it when I am talking about very high levels indeed at frequencies an individual..

(6) ..hear(which may be above 20 kHz if their hearing can achieve that). It is talking abut extreme levels you would not encounter in a public space so don’t be unduly alarmed. They levels you encounter will bring annoyance, anxiety, headaches (possibly as result of tensing...

(7)...neck muscles etc). Where I said if you can hear an ultrasonic frequency it will adversely affect you, that was in context of there being a narrowing window in amplitude as you do to higher frequencies, whereby the amplitude that is annoying is only a little louder than...

(8)..the amplitude at which you can just hear it (the amplitude difference between the two thresholds is much larger at lower frequencies). So all in all I would communicate a more contextualized message than CNN, with it’s limited space, edited up for me.

Thanks for the info! FWIW, the ones I'm talking about here are sold as rat deterrents, and claim to put out 19kHz at 136dB. They all all over Tokyo. I wrote a rather enthusiastic thread about them recently.https://twitter.com/marcan42/status/1162697281474142208?s=19 …

I can definitely hear the sound and it causes me physical distress (though not debilitating, it's not harmless either); I've also heard many stories of people being affected but not realizing that the cause is a sound. I'm worried about it actually causing lasting hearing damage.

It's insidious, because the inability to localize the sound, and not being used to sounds that high, make it difficult to immediately recognize it as such. I've been in places where something felt off but only upon getting close enough to the emitter did I realize what it was.

I'm interested in taking calibrated measurements of this. Do you have any suggestions as to what to use for a calibration standard? I have an omni measurement microphone that should be flat enough, I'm thinking maybe I can calibrate the overall gain against a sound level meter.