Why can I hear this beep at 6 kHz and others cannot?

1

During a studio recording, I heard a beep and paused the recording. I played it back and neither the actress, sound technician, or assistant director could hear it. I imagined that it could be the remote control unit of the air conditioning, which was turned off but still listening.

Listening to the tapes, I heard it again and found it in the frequency spectrum:

frequency spectrum

It is very, very faint, so here is the same picture with gamma correction and a note on the beep:

frequency spectrum, adjusted

Here is the recording.

I asked a musician and he didn't hear it either. I did frequency repair and it almost worked; doing it on the voice as well made it sound tinny. If I delete all frequencies above 6k, the voice sounds muffled; if I delete frequencies below, the voice becomes unintelligible. At 6k, it should be well within the frequency range of a human ear:

Frequencies capable of being heard by humans are called audio or sonic. The range is typically considered to be between 20 Hz and 20,000 Hz.

Why can I hear this beep sound and several people cannot?

miguelmorin

Posted 2020-08-07T15:11:23.977

Reputation: 185

Are you member of the K-9 family? – Alaska Man – 2020-08-08T21:43:38.143

@AlaskaMan What is the K-9 family? – miguelmorin – 2020-08-10T09:34:12.403

k-9 is American slang for 'canine' i.e. a dog. – Hobbes – 2020-08-11T06:41:23.353

Lol! No, I'm a real human curious about a newly discovered ability. That also explains trouble sleeping at night... – miguelmorin – 2020-08-12T09:55:11.493

Answers

2

I listened to the file several times and couldn't hear it. In a spectrum analyzer, I can see what you're referring to. It's at -90 dB, so you'd have to crank up the volume pretty far to be able to hear it.

Because the speech volume in the recording is at -20 dB, most people will set the volume to a level where that's comfortable to listen to, and the beep will disappear below the noise floor.

The spectrum indicates the sound is in a narrow frequency band (or even a single frequency), so you might be able to get rid of it with a very narrow notch filter.

enter image description here

Hobbes

Posted 2020-08-07T15:11:23.977

Reputation: 1 478

Can you hear it if you increase the volume on that part only? I am also able to notice other background rumble when listening with volume at level comfortable for me and others cannot; does that simply mean that I have more sensitivity to background noise? – miguelmorin – 2020-08-08T10:23:30.227

Yes. I can also hear it if I listen to the unedited recording on my IEMs with the volume a bit above normal (doing this on my laptop, so can't say how much above normal). – Hobbes – 2020-08-08T10:43:07.283

It's entirely possible your hearing is more sensitive than others. You're probably also more used to how the studio and its equipment sounds than the others. – Hobbes – 2020-08-08T10:46:59.240

Thanks. This was my first time recording in studio. I was bothered by it and stopped recordings, so I got good alternate tape anyway. – miguelmorin – 2020-08-08T10:50:09.070