What is the proper loudness for listening?

Those two items on each side of your head will be the guide as to how loud you can go with the sound. Your room will also dictate this and whether you're listening alone, what time of day/night you are listening, etc. If you plan on listening into old age as I am, then don't go overboard on the volume control!

@snilf Wrote:

Thank you, @ditusa. These are very informative links.

For one thing, low frequencies are felt as well as heard. Surely you (ditusa) are not advocating for measurements that ignore low—and high, for that matter—frequencies!

Your welcome. No, I am not advocating for measurements that ignore low and high frequencies. The Department of Labor bulletin #334 I posted about OSHA standards is their standard for safe levels, they don’t care about audio, like you and I do. I.e. full frequency bandwidth from 20Hz to 20KHz. They only care about safety, bass frequencies below 100Hz are not as detrimental to our hearing as frequencies above 100Hz. You are correct, frequencies below 500Hz are felt as well as heard, so yes C-weighted dB(C) would be better for audio.

FWIW, I bought a pair of JBL 4343’s in 1979 for my home stereo, see JBL brochure below last page top right hand corner caution:

Mike

https://www.lansingheritage.org/html/jbl/specs/pro-speakers/1977-4343.htm

Huh...what??...speak up

75 avg/dB 85 dB peaks, treated room with a 24 dB noise floor A weighted 

I mostly listen to jazz on vinyl, average 80db with peaks of 96db-sh