"some loud tone, usually in the low decible range"

errr...that's an oxymoron. Decibels is a measure of loudness. If it's loud, it's higher decibels. Quiet is lower decibels.

This wikipedia article explains more than you'd want to know, and has a chart giving a sample of conditions at various decibel levels.

http://en.wikipedia.org/wiki/Decibels

Also, I should have been more precise, "spontaneous otoacoustic emissions"
^^^^^^^^^^^
From what I've read about SOAE's is that they are very pure tones.

from: http://www.emedicine.com/ent/topic372.htm
"nonevoked response usually is measured in narrow bands (<30 Hz bandwidth)"
"usually span the 500- to 7000-Hz frequency range"

Here's some more links:
http://www.capitolent.net/otoacoustic-emissions.htm
http://www.otoemissions.org/definitions/SOAE.html
http://en.wikipedia.org/wiki/Otoacoustic_emission
http://www.otoemissions.org/

Brian