I made test sound samples some time ago, they are useful to find what -60dB is like:
https://www.kvalsvoll.com/Articles/TestSignals/Loudness 880hz -20dB sweep -60dB.flac
Here, a 880Hz tone is at -20dB is mixed with as tone sweep at -60dB. So the sweep in the background (which clearly is audible, even at fairly low volume) is -40dB below the 880Hz tone.
Here it is -60dB below that same tone - now the level of the sweep is -80dB, and now it is just barely audible at low volume:
https://www.kvalsvoll.com/Articles/TestSignals/Loudness 880hz -20dB sweep -80dB.flac
I have samples at -100dB and -120db as well, the -100dB is barely audible if you turn up the volume (0dB):
https://www.kvalsvoll.com/Articles/TestSignals/Loudness tone sweep -100dB.flac
All those samples can be found in the
https://www.kvalsvoll.com/Articles/TestSignals/
catalog.
Now you can also find the samples with tone sweep only, and then you can hear the -120dB, it is just a matter of turning up the volume to dangerous levels.
Note that the next sample in the list below -120dB tone sweep is a 0dBFS sweep, just mentioning, in case.. I think you get the idea of a potentially rather unpleasant scenario.