- 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)
| Decibel Level | Sound |
| 10 | Light Whisper |
| 20 | Soft Conversation |
| 30 | Normal Conversation |
| 40 | Light Traffic |
| 50 | Loud Conversation |
| 60 | Busy Office |
| 70 | Traffic, train |
| 80 | Subway |
| 90 | Heavy Traffic, Thunder |
| 100 | Jet Plane takeoff |
| 120 | Pain Threshold |
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