| A | B |
|---|
| sound energy | the energy carried by sound waves |
| vacuum | the volume of space where there are no particles |
| supersonic | faster than the speed of sound |
| subsonic | being or moving at a speed below that of sound |
| noise | unwanted sound |
| loudness | the measure of the intensity of sound |
| decibel scale | scale to measure the loudness of sound |
| decibel meter | an instrument used to measure the loudness of a sound |
| ear defenders | cups lined with sound-deadening material (look like thermal earmuffs or headphones) which are worn as hearing protection; also called acoustic earmuffs |
| *sonic boom | a shock wave of compressed air caused by an aircraft traveling faster than the speed of sound |
| *Doppler effect | change in the apparent frequency of a wave as observer and source move toward or away from each other |
| *tinnitus | a ringing or whistling sound in the ears not caused by an outside stimulus |
