Both of you do yourselves a great big favor, and go to Rat Shack and ask them to sell you the Analog version of their Sound Level Meter.
It ain't perfect by far, but it's only about $40 as compared to about $1000 for the serious ones, and the main thing is it's reported to be accurate within about 2 dB when compared to the big boys - (up to maybe 4KhZ or less) (Actually, the main thing is that it's REPEATABLE, and that's what you want. The human ear "gets used to" whatever average level of noise is around, so it's NOT reliable as a reference for VOLUME...)
Point is, Bradleeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee heard right.
OSHA says you can expose yourself (oooh, fun) to 90 dB for up to 8 hours with no hearing protection without damage.
The Fletcher-Munson curves of human hearing response are the flattest at around 85 dB, "C" weighted.
The more consistent your monitoring levels, the more consistent frequency spread your mixes will have.
Sooo, for least hearing damage, best EQ balance and most consistent mixes, you should monitor at 85 dB, "C" weighted, and MAINTAIN that level as you change various track levels in the mix. That way, you don't automatically think that just because you raised the kick drum 2 dB it's really "better" it's only LOUDER. (Most knowledgeable sound people know this - if you're selling ANY audio component, make the one you want to sell just a tiny bit louder in any A/B test, and that's the one they'll buy)
When I'm mixing, I keep the SLM on and check it after any noticeable "tweak" to the mix - if the level changes from 85, I re-adjust the master back to 85. Works for me... Steve