It's a "no brainer"... auditory acuity (hearing) varies from person to person, young to old ... by frequency etc. "Loud" to one person can be "acceptable/quiet" to another person. The only useful way to measure sound is the objective way, by decibels with a rough published spectrum (hi, medium and lo frequencies) that each consumer can evaluate, if noise is truly important to them. I like the idea of a MP3 recording.