Textbook Notes (368,317)
Canada (161,798)
Psychology (9,695)
PSYB51H3 (306)
Chapter 9

Chapter 9

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Matthias Niemeier

Chapter 9: Hearing: Physiology and Psychoacoustics What Is Sound? Sounds created when objects vibrate Vibrations of object cause molecules in objects surrounding medium to vibrate as well o Vibration causes pressure changes in medium o Pressure changes are waves Sound waves travel at particular speed depending on medium, moving faster through denser substances When jet plane travels faster than speed of sound, plane catches up to and passes fronts of sound waves it is creating o Sound waves combine into shock wave, or huge pressure fluctuation o When shock wave reaches ground, we hear sonic boom Basic Qualities of Sound Waves: Frequency and Amplitude Amplitude (intensity): magnitude of pressure change in sound wave- difference between highest pressure area and lowest pressure area Pressure fluctuations can be very close together or spread apart over longer periods Frequency: how quickly pressure fluctuates Hertz (Hz): measure for frequency. 1 Hz equals one cycle per second Amplitude associated with loudness: the more intense a sound wave is, the louder it will sound Frequency associated with pitch: low-frequency sounds correspond to low pitches and high-frequency sound correspond to high pitches If young and careful about exposure can hear from 20 to 20 000Hz Decibels (dB): measure for physical intensity of sound o Define difference between 2 sounds as ratio between 2 sound pressures o Each 10:1 sound pressure ratio equals 20dB and 100:1 ratio equals 40dB Sine Waves, Complex Tones, Fourier Analysis Sine wave (pure tone): simplest kinds of sounds o Air pressure in sine wave changes continuously at same frequency Period: time taken for one complete cycle of sine wave Phases: relative position of 2 or more sine waves Complex tones: sound wave consisting of more than one sinusoidal component of different frequencies o Human voices, birds Fourier analysis: individual sine wave components of complex sound o Spectrum: shows intensity of each sine wave frequency found in complex tone Summarize results of Fourier Harmonic spectra: typically caused by simple vibrating source o i.e. string of guitar or reed of saxophone o each frequency component in such sound called harmonic Fundamental frequency: lowest frequency component of sound Timbre: describe the quality of sound that depends on relative energy levels of harmonic components Basic Structure of Mammalian Auditory System Outer Ear Sounds collected from environment by pinna: curly structure on side of head that we typically call ear Only mammals have pinnae Ear canal: sound waves funnelled by pinna into and through canal o Length and shape of ear canal enhance sound frequencies between 2000 and 6000 Hz o Main purpose to insulate structure at end tympanic membrane (eardrum) from damage Damaged eardrum will heal itself, like skin Pinna and ear canal makes outer ear www.notesolution.com
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