This is from the PAS Forums. The guy is living in Germany

[So I am carrying out an experiment in my side yard. We have a serious problem with moles burrowing under the surface and leaving big mounds of excavated dirt -- about 15 of them in a small area less than 20 feet in diameter.

Poisons and various chemical repellents are illegal in Germany. My landlady mentioned that Germans buy a kind of low-frequency sonar system that plants into the ground and drives the moles away, while being inaudible to humans. The alternatives consist of sticking in children's toy pinwheels (dumb looking) or using a solution of castor oil. I have no inkling of where to find castor oil in this day and age.

So I took apart an old set of headphones from my studio, plugged my Dr. Beat into a wall outlet to save batteries, connected it to the ear cups and ran them out to the yard using a long extension. I put the earcups against the ground, weighted them down and covered them with plastic against the rain, then placed an aluminum pan over them to act as a resonance chamber. Inside the house, I set the Dr. Beat to produce a constant A=440 tone, and was still able to close and lock the studio door.

It is madly "sounding away" right now, around the clock. My only concern was that 440 might not be nearly low enough, but it seems to be working so far. No digging for the past week.

Percussionists just do what they have to do.]

Wow, that's actually a pretty good idea lol.

thats funny

thats really cool.
hope it continues to work.
do you have a spare met for practice? :P

excellent idea.