Hearing Physiology and Psychoacoustics

Hearing Physiology and Psychoacoustics - 9 9 Hearing:...

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9 Hearing: Physiology and Psychoacoustics Chapter 9 9 Hearing: Physiology and Psychoacoustics • The Function of Hearing • What Is Sound? • Basic Structure of the Mammalian Auditory System • Basic Operating Characteristics of the Auditory System • Intensity and Loudness • Hearing Loss 9 The Function of Hearing The Basics: – Nature of sound – Anatomy and physiology of the auditory system – How we perceive loudness and pitch – Impairments of hearing
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9 What Is Sound? Sounds are created when objects vibrate. Vibrations of object cause molecules in object’s surrounding medium to vibrate as well, which causes pressure changes in medium. 9 What Is Sound? Sound waves travel at a particular speed – Depends on medium – Example: Speed of sound through air is about 340 meters/second, but speed of sound through water is 1500 meters/second 9 Characteristics of Sound: Frequency Frequency: For sound, the number of times per second that a pattern of pressure change repeats. Frequency is associated with pitch. Low-frequency sounds correspond to low pitches, (e.g., low notes played by a tuba). High-frequency sounds correspond to high pitches, (e.g., high notes from a piccolo).
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9 Characteristics of Sound: Amplitude Basic qualities of sound waves Amplitude: Magnitude of displacement of a sound pressure wave. Intensity: Amount of sound energy falling on a unit area. Loudness: The psychological aspect of sound related to perceived intensity or magnitude. 9 Intensity of Environmental Sounds 9 Characteristics of Sound: Amplitude Humans can hear across a wide range of sound intensities. Ratio between faintest and loudest sounds is more than one to one million. – In order to describe differences in amplitude, sound levels are measured on a logarithmic scale, in units called decibels (dB). – Relatively small decibel changes can correspond to large physical changes (e.g., increase of 6 dB corresponds to a doubling of the amount of pressure).
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9 Characteristics of Sound: Timbre Timbre: Psychological sensation by which listener can judge that two sounds that have same loudness and pitch are dissimilar. Harmonic spectra: Typically caused by simple vibrating source, (e.g., string of guitar, or reed of saxophone). First harmonic: Fundamental frequency-lowest frequency component of the sound. 9 Harmonic Sounds with the Same Fundamental First harmonic 9 What Is Sound? One of simplest kinds of sounds: Sine wave, or pure tone. Waveform for which variation as a function of time is a sine function. Time taken for one complete cycle of sine wave: Period.
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9 What Is Sound? There are 360 degrees of phase across one period. 9 Complex Sounds Sine waves: Not common everyday sounds because not many vibrations in the world are so pure. Most sounds in world, e.g., human voices, birds, cars, etc. . All sound waves can be described as some combination of sine waves. Sine wave
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Hearing Physiology and Psychoacoustics - 9 9 Hearing:...

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