Me again. I've recently edited a video where I had to keyframe a pure sine tone (1000 Hz) so that it beeps on and off. While doing so I noticed two issues:
The composite shot was set to 1280 x 720 with 30 fps and Square Pixels. No fog enabled, motion blur left at the standard values.
I don't know if this issue is truly a bug or rather an effect of digital audio? The tone was generated in Audacity with an Amplitude of 0.8 (peak amplitude at -2 dB). The file was exported as a WAV 32-bit float PCM. Maybe -2 dB are too loud in the first place?
My System specs: