AUDITION AC Brown page 1 A7bINTRODUCTION Terms: external auditory canal = external auditory meatus eardrum = tympanic membrane auditory tube = Eustatian tube A. Transducer Function of Ear: to convert sound (pressure) waves in the range 20 - 20,000 hz (hertz, cycles/second) into action an action potential pattern that permits sensation of the incident sound and a recognition of its parameters B. Psychophysics of Sound 1. Sound parameters PhysicalUnitPhysiologicalFrequency Hertz (hz, cycles/second) Pitch Power (or amplitude) bel or decibel (db) Loudness Shape of wave harmonic content (freq. spectrum) Timbre Note: “pure tone” = sine wave
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AUDITION AC Brown page 2 A7bINTRODUCTION (continued) B. Psychophysics of Sound (continued) 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: the auditory system is most sensitive at the midrange of frequencies (500-3000 hz) and progressively less sensitive at higher and lower frequencies 4. Audiogram: Hearing threshold compared to normalas a function of frequency a. determined by measuring hearing threshold compared to normal at several frequencies b. 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 c. each ear is tested separately