silent flight

In the world of niose restrictions this may seem to be an unusual question. At several fun flys I have noticed a loud prop noise on a
high speed pass that I thiink is caused by the prop cavitating in the air or possibly the tips going sub sonic. The last guy I talked to about it was flying an old Tartan twin turning about 8000 RPM. He went silent when I asked him what I needed to do to duplicate the sound. Currently I am running a G-45 w/ a Bolly 18-10 composite. I know the prop is on the small side for the engine but I want get max rpm if that is what it takes. I am not into 3D, don't really care about maximun thrust. We fly in a very rural area so no one would be bothered. I have noticed a similiar noise on full scale aerobatic planes at airshows. I just like to hear the bark. Can anyone tell me what it takes? I even offered to buy the last guys model.

aerowoof

you mran super sonic as the are allready sub sonic