Orange County NC Website
Browse       Search
--- 011111 <br /> Your ear has an amazing dynamic range. At the low en'd of the range, <br /> you can hear very faint sounds of less than 10-dB sound pressure level , <br /> yet you can also hear and identify sounds of more thani100-dB sound <br /> pressure level. For example , sitting inside your house on a summer <br /> evening, you can hear a cricket chirping in your gardenland , minutes <br /> later, a commercial airliner flying overhead . The plane's sound power <br /> is many times greater than the cricket' s - but you hear and distinguish <br /> them both. The levels of a number of common sounds are shoWn in Fig. 7 . <br /> 1 <br /> * *I <br /> In your work with airports , you will often be disctissing noise <br /> abatement . Remember , as you do , that it takes a lot of noise reduction <br /> to make a perceptible difference in sound. When a sound is ecreased by <br /> 1 <br /> about 10 dB in level , people judge it to be about halt as loud as <br /> before. Yet to achieve that change , 90% of the sound energy must be <br /> 411 removed - a challenge! <br /> 1 <br /> Aircraft noise is one of the two major sources of noiseIin America; <br /> the other is freeway traffic . More than 16 million Americans are <br /> exposed , each day, to an average sound level of more than 60 dB because <br /> of aircraft operations , And , as you are aware , many doOt like it . <br /> 411 ; <br /> 16 <br /> 1,1t ;1-.7 '-'4*•11M.; - <br />