At 10:26 AM 11/19/2001 -0800, you wrote: > >The post equating Noise to Turbulence deserves another mention. There really >is very little energy in the sound itself. Were it not for the associated >Turbulence, sound would be trivial. > >Bill Swingle >[EMAIL PROTECTED] >Janesville, CA >
At sound pressure levels you can encounter flying models, you are right. Sound has very little energy. The sound is generated by vortices which can contain a lot of energy. Therefore, sound can be considered to be a symptom of drag even though the noise does not make a significant contribution. About 30 years ago, I designed a small low noise wind tunnel for the express purpose of studying noise generated by perforated walls required for transonic wind tunnel testing. Unfortunately, these walls also generate a lot of noise. I spent two years measuring noise levels and finding a way to reduce the noise level to that of a solid wall wind tunnel. In this investigation, I measured noise levels in excess of 150 db at a Mach number of 0.8. At these sound pressure levels, I was able to obtain schlieren photographs of sound waves that looked like shock waves normally seen at Mach numbers above 2. Chuck Anderson RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
