How to I map db to the volume on a smartphone?
There are apps. I just tried "Decibel Meter" by Xiangyi Liu on my iphone. Free. Seems to work.
Update - just tried it. 90-100db on the tube (Victoria line), 102 when they make announcements, 60db in the park, 25 in my room.
His research on hearing loss, in particular hearing loss of musicians, deserves wide exposure for anyone considering making a career out of using their ears.
From one of his publications I use the following as a rule of thumb:
80db * 40hrs/week = permanent hearing damage
83db * 20hrs/week = permanent hearing damage
86db * 10hrs/week = permanent hearing damage
91db * 5hrs/week = permanent hearing damage
94db * 2.5hrs/week = permanent hearing damage
Further reading from Dr. Chasin: http://www.marshallchasinassociates.ca/hearing_articles.htm