B. Psychophysics of Sound

1. Sound parameters

Physical	Unit	Physiological
Frequency	Hertz (hz, cycles/second)	Pitch
Power (or amplitude)	bel or decibel (db)	Loudness
Shape of wave	harmonic content (freq. spectrum)	Timbre (envelope)

Note: "pure tone" = sine wave

2. Units of Power/Loudness/Intensity: decibels (db)

Note: when two sound sources are present simultaneously, the louder tends to mask (suppress perception of) the softer

3. Audibility Curve: Absolute hearing threshold as a function of frequency

4. Audiogram: Hearing threshold compared to normal as a function of frequency

a. determined by measuring hearing threshold compared to normal at several frequencies
b. obtained with an audiometer
c. on an audiogram, normal sensitivity at a given frequency is plotted as 0 db; degree of hearing loss at each frequency is noted by the distance below the 0 db line
d. each ear is tested separately

Special Bonus!  ACB audiogram ==>

Note:  Rough test:  rub thumb & index finger near ear

Note:  Noise-induced hearing loss and the dentist ==>