IMO dB is probably the most abused "unit" around. (*)
It can be used well (I avoided saying "properly") as in Offcom licences, "all power levels are expressed as dB relative to 1 W", then each number is labelled dBW.
But generally the reference is implicit at best. Even when explicit the reference is often vague, eg. "almost silence". (At least they didn't say "silence", as that could really muck up the maths and make dB impossible.)
To be fair, if you have access to the ISO standard you can find out that near silence is probably an A-wieghted threshold of hearing for a standard listener, but the details tend to get lost when people produce tables like this. (Incidentally, IMO A wieghting is an honest attempt to do something useful, but even that has changed over the years.)
In electronics it was often unclear whether people were quoting power ratios or voltage ratios and you seem to get a similar confusion in sound, when people sometimes talk of sound pressure levels, rather than power levels.
Coming nearer to OP's issue, my bins are labelled with LwA dB, which does seem to be a well defined number, though I can't understand what it actually means. The rubbish bin and the green waste bin are both 99 LwA dB, but the recycling bin (middle sized of the three) is only 92 LwA dB. I don't know how they make all that noise? They usually stand there in silence (except for the birds.) If I drop something in when they're empty, there's a bit of a bump, slamming the lid makes about the same noise and the loudest is when I drag them across the gravel drive. If theyre talking about the noise when they're emptied, you can't hear the bin because the collection truck drowns out everything else.
I did find a reassuring explanation of sound levels in domestic appliances, summarised here
(*) If you think there's a worse case (maybe SWARS, RMSWatts, WattsPMPO?) someone could start another thread and we could all let off steam about examples of misuse or our pet hate units?
