The unit of sound pressure. Originally called a bar, but now termed by the full expression. At the threshold of hearing, the acoustic force per unit area is 0.0002 dynes/cm2
"Thank you so much! I have received my new CD transferred from a very old 45rpm record. It is the accompaniment to a selection of trumpet solos that I loved playing 55 years ago! Simply listening to the CD by itself brought tears to my eyes, as I found I was also “hearing" my solos as well from memory. I’m practicing and will soon be back ..."