Pop Quiz: December 2006
Test Your Knowledge of Outdoor Acoustics
TRUE OR FALSEThe only place where the inverse square law is truly accurate for calculating sound pressure level (SPL) attenuation is outdoors. When outdoor humidity levels are high, sound transmission will be significantly reduced. The “Doppler Effect†is only heard outdoors. The velocity of sound varies with temperature. ANSWERS
1. FALSE. An anechoic chamber produces nearly the same effect. However, in most indoor spaces, the presence of sound reflections from surfaces or reverberation will add to the total SPL, thus resulting in less measured attenuation than the inverse square law will predict.
2. FALSE. Attenuation is actually greater at lower relative humidity levels.
3. FALSE. The Doppler Effect may be more commonly heard outdoors because it requires either the source or listener to travel a significant distance.
4. TRUE. The higher the temperature, the faster sound will travel.
