In addition to my posts above on the audibility of noise from audio electronics I find it quite intuitive that two power amplifiers with different distortion profiles below -80 db can subjectively sound different.
Given Robert’s observations on ambient room noise at -40 db how is it possible to determine the above? Major hifi brands trade on the fact their customers like the sound of their products. The distortion is not however at the ambient noise level of a room.
As the great Nelson Pass says somethings cannot be explained by measurements alone.
Edit attached is excerpts of an acoustic glass application guide.
The guide does stage the db level in inside of the glass in not necessarily the noise level in the room and other sources of noise for example a ceiling or air conditioning might effect the noise level in the room. Board rooms, court rooms are generally quiet places but it’s the noise made by occupants that’s the issue.
Having spent many hours in all sorts of secure environments l can state un categorically its the other people in a room that are the source of noise. I’m talking about quiet rooms, bank vaults. Air con rustles paper work. When people move their clothes they make a noise!
This type of noise is distracting.
When l have the time l do my critical listening late at night. It’s simply much quieter and that is when a systems noise floor really comes into play.