- Absorption Coefficient- Denoted by alpha (units of inverse meters) and “a” (dB/m). This constant measures the sound-absorbing ability of a material. The values go from about 0.01 for marble slate to almost 1.0 for the long absorbing wedges that are used in some anechoic sound chambers.
- Anechoic Sound Chamber- room in which the walls, ceiling, and floor all are covered with sound absorbing materials shaped to maximize sound absorption. Echoes effectively do not exist in such a chamber
- Decibel- logarithmic unit used to gage sound level. Subtracting three decibels translates to reducing the intensity by 50%. Human ears, however, perceive sound that is 10 times less intense as being half as “loud”. In other words, a difference of 10 dB will seem to be twice as loud or quiet.
- Hertz- unit of frequency (inverse seconds). AKA cycles/second.
- Infrasonic- sound lower than 20 hertz
- Medium- the material that something travels through
- Octave- difference in pitch equal to a doubling of frequency
- Threshold of pain- 120 dB- the level that goes from discomfort to pain and hearing loss
- Tone- a definite pitch
- Ultrasonic- frequencies about 20,000 Hz (20 kHz)
|90||Heavy Traffic, Thunder|
|100||Jet Plane takeoff|