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Hunting high-pitched noise in the lab

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RBBVNL9:
On this forum, regularly people talk about noise coming from devices in their lab, like hum, noise from the fans, etc. Lately, I have been annoyed by some of my devices producing very high-pitched, audible noise. In this video, I hunt the suspects and analyze the noise they produce.

pcprogrammer:
Just named another beeping device in another thread :-DD

The FNIRSI-1013D. Turn down the brightness and there it is. Not sure about the frequency but it will be up high near what you measured from your power supply. My hearing is still very good and above what is normal for my age :)

james_s:
I have an audio spectrum analyzer app on my phone that I've used for this sort of thing. At my age I can no longer easily hear much over about 15kHz but I remember when I was a kid the whistle from the horizontal deflection on some CRT monitors would just about drill a hole in my head. I remember one of my highschool teachers being mystified that I could walk into the classroom and say that someone had left one of the monitors on in the video production station, she was an older lady and had no idea how I could tell but I could hear the whine from out in the hallway.

RBBVNL9:

--- Quote ---I have an audio spectrum analyzer app on my phone that I've used for this sort of thing.
--- End quote ---

Which one? I use the iOS app "Analyzer" from dspmobile.com, a very capable app in many ways to measure sound level (with the proper selection for A/B/C weighting and various responses, 'semi-calibrated' for various iPhone models, and more). You need to pay a fee but it's worth it.,  It also has a spectrum mode, but I found the 10kHz to 20kHz range was made up of only 2 measurements so I went to look on.l..


--- Quote ---At my age I can no longer easily hear much over about 15kHz but I remember when I was a kid the whistle from the horizontal deflection on some CRT monitors would just about drill a hole in my head. I remember one of my highschool teachers being mystified that I could walk into the classroom and say that someone had left one of the monitors on in the video production station, she was an older lady and had no idea how I could tell but I could hear the whine from out in the hallway.
--- End quote ---

Certainly recognize this ;) I could also tell upstairs whether the TV downstairs was on or not. I live in The Netherlands (PAL 625 lines standard), so the line frequency tone there was 15625 Hz (625 lines × 50 Hz ÷ 2 because of interlacing).

I see you are from the US, so that must have been NTSC. What is the line frequency for that standard?

I wanted a rude username:

--- Quote from: RBBVNL9 on September 19, 2021, 06:29:31 pm ---Which one?

--- End quote ---

The open source Oscilloscope app is excellent for this application, as it has a precise spectrum analyser with near-real-time refresh rate (much quicker than in the video). I've also used its oscilloscope mode to calibrate engine RPM. May only be available from the open source F-Droid app store though.

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