Impact of sound - in the tank

[thomb]

If I put my ear up to the tank, I can hear noise from the powerheads. Its normal sound from them - they are what they are. But it does make me wonder....
http://www.dosits.org/animals/effectsofsound/effectsofsoundonfish/

It's not unlike diving when a boat is near.

I don't have Ecotechs anymore - can someone with them put their ear to the tank and tell me what they here?

I didn't have the room for MP40's I had - traded in got Tunzes, which are "serviceable" but much bulkier than I'd like. But I am an Ecotech snob I guess. I might be able to fit MP10's...