All I can say is so much for Leica pushing the idea their cameras are so quiet after seeing the IIc wind up being the loudest camera of the bunch.
This got me thinking; I have a IIIg, If and IIIf that should all be functionally the same, but sound
very different. The IIIg's shutter sounds soft and almost whisper quiet, the If is a little bit louder than that, and the IIIf has sounded like a sharp clap ever since it was last serviced in 2016 (I think the shutter may have been over-tensioned to get it running to spec).
So I set up a test with a Zoom H1 audio recorder stood on a table and all three cameras positioned around it, lenses removed, the lens mount on each camera positioned exactly 30cm from the microphone on the recorder, and each shutter set to 1/500.
Then I took the audio file and uploaded it to
https://www.misha.studio/waveformer/ to produce a graphic representation of the audio.
This is the result (with a bit of editing to increase the height of the wave forms - equally, of course! - and close the gaps between them for easier comparison):
The difference is basically nominal, but it is there - and it definitely seems much greater with the camera right next to your face. I suspect that if the IIIf was re-serviced and the shutter tension was bought down, it'd be more in line with the IIIg.
Also, I'm now kicking myself that I didn't dig out a Pentax MX and a big clunky Zenit to produce comparative waveforms for those!