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CHAPTER 11Sound stimulusSound – physical stimulus or perceptual response1. physical stimulus – sound is pressure changes in the air or other medium2. perceptual definition – sound is the experience we have when we hear-occurs when the movements or vibrations of an object cause pressure changes in air, water, or any other elastic medium that surrounds the object-changes in air pressure = vibration-travels in waves-condensation – pushes surrounding air molecules together, causes slight increase in the density of molecules near the diaphragm-results in a local increase in the air pressure that is superimposed on the atmospheric pressure-rarefaction – diaphragm moves back in, air molecules spread out to fill in the increased space, decreased density ofair molecules caused by rarefaction causes a slight decrease in air pressure-repeating this process = creates a pattern of alternating high-and-low pressure regions in the air as neighboring air molecules affect each other -sound wave - pattern of air pressure changespure tones-occurs when pressure changes in the air occur in a pattern described by a mathematical function called a sine wave-tone with this pattern of pressure changes are occasionally found in the environment-amplitude – the size of the pressure chance-different in pressure b/w the high and low peaks of the sound wave-associated with our experience of loudness  higher amplitudes associated with louder sounds-amplitude (physical)  loudness (perceptual)decibel – a unit of sound which converts the large range of sound pressure into a more manageable scale-SPL sound pressure level – indicates we have used the standard pressure of 20 p0-level/sound level – when referring to decibels or sound pressure of a sound stimulus-frequency – the number of times per second that the pressure changes repeat-the number of cycles per second the change in pressure repeats-physical measure associated with our perception of pitch  higher frequencies associated with higher pitches-hertz (Hz) - units, 1 Hz is 1 cycle per second-humans can perceive frequencies ranging from about 20 Hz to 20,000 Hz and most sensitive at frequencies b/w 2,000 and 4,000 Hz = range of frequency important for understand speech -frequency (physical) and pitch (perceptual)pressure changes: complex tonesperiodic tone - property of repetition for complex and pure tonesfundamental frequency - repetition rate of a complex toneadditive synthesis – use to build a complex tone, a number of sine-wave components are added together to create the complex tone-starting point – a single pure tone which has a frequency equal to the complex tone’s fundamental frequency-then – add the fundamental frequency that is a multiple of the fundamental frequencyharmonics – additional tones to a tonefirst harmonic - fundamental (first)-adding the first harmonic and higher harmonics = the waveform of the complex tonefrequency spectra – represent the harmonic component of a complex tone -distance between harmonics = fundamental frequencypitch – perceiving a tone as high or lowperceiving soundloudness - quality most closely related to the amplitude or sound pressure (also called the level of an auditory stimulus)-often associated with decibels-decibels = physical measure and defined in terms of pressure not perception, loudness = psychologicalpitch - perceptual quality described as “high” or “low”-the attribute of auditory sensation in terms of what sounds may be ordered on a musical scale-closely related the physical property of frequency-low fundamental frequencies are associated with low pitches and vice versatone height - perceptual experience of increasing pitch that accompanies increases in tone’s fundamental frequencytone chroma - notes with the same letteroctave – a higher interval every time we pass the same letter-tones separated by octaves have the same tone chroma-notes with the same chroma have fundamental frequencies that are multiples of one anothereffect of the missing fundamental - constancy of pitch even when the fundamental or other harmonics are removedperiodicity pitch - pitch that we perceive in tones and that has had harmonics removedrange of hearing - the specific range of frequencies we hear sound inaudibility curve - the human range of hearing is depicted, indicate the threshold for hearing determined by free-field presentation (listening to a loud speaker) versus frequency auditory response area - area about audibility curve, can hear tones that fall in this area-below audibility curve = can’t hear tone-upper boundary of the auditory response area is the curve marked “threshold of feeling” – tones with these high amplitudes are ones we can feel = become painful and can cause damage to the auditory systemloudness-audibility curve and auditory response area indicate the loudness of pure tones from sound pressure and frequency-to determine loudness of tone – need to know both its dB level and frequency-equal loudness curve - explains the relationship b/w loudness and frequency, indicate the number of decibels that create the same perception of loudness at difference frequenciestimbre-quality that distinguishes between two tones that have the same loudness, pitch and duration but still sound different-closely related to harmonic structure of a tone-difference in harmonics of different instrument is one factor that causes musical instruments to have different timbresattack - the buildup of sound at the beginning of the tonedecay - the decrease in sound at the end of the tone-pure tones and tones produced by musical instruments are all periodic sounds  pattern of pressure changes repeatsaperiodic sounds - sound waves do not repeat the ear1. must deliver the sound stimulus to the receptors2. it must transduce this stimulus from pressure changes into electrical signals3. it must process these electrical signals so they can indicate qualities of sound source such as pitch, loudness, timbre, and location-divided into 3 divisions – outer, middle, and innerouter earpinnae - structures that stick out from the sides of the head-important in helping us determine the location of sounds and important for those who wear eyeglasses  part of theear we could most easily do withoutcapture sound-localize sound-sound waves first pass through the outer ear - consists of pinna and auditory canalauditory canal - tubelike structure, protects the delicate

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SC PSYC 450 - CHAPTER 11 Sound Stimulus

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