Letter: Letter writer misunderstands metrics of sound


In an attempt to discredit my analysis of the three reports on jet noise referenced, Mr. Monson does not appear to have basic math or physics knowledge. My numbers are correct and easily proven with math. Mr. Monson also seems to think noise attenuation rate is a function of the noise source and not the density of air and temperature.

My calculation was at atmosphere and temperature based on International Standards Atmosphere a noise source such as a jet engine that could produce 150DB.

It is also interesting that Mr. Monson twists the facts and thinks he knows which airplanes the Navy needs to keep America safe. The information he references is more future and budget related. Would the Navy like to have new planes in the future, clearly. Faster smarter more expensive planes that could well be even louder.

However, none of this is actually relevant to Mr. Monson’s group. They do not want the Navy to prepare for carrier landings at OLF prior to Growler deployments. They seem to be willing to use any means possible to claim, now that I moved here, move the jets out of my back yard.

The attenuation of sound levels as it travels away from a noise source is dependent on both temperature and density and not how loud the source is. As altitude increases, the air becomes less dense and the temperature decreases. E.g. Using the ISA base, our density for calculations is 1.225 kg/m3 with a temperature of 20 °C. At 5000 feet the temperature is approximately -17.5 oC and the density is 0.74 kg/m3.

As a result, the level of attenuation for a 150DB noise will be even higher than my calculation values. The attenuation over any distance is the same for all audible noise sources. The noise DB level at the observer’s location will clearly increase with the increase of the noise source DB level, but attenuation in the air remains the same for a given temperature and density.

Terry Sparks

Oak Harbor