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PSYB51H3 (306)
Chapter 9

Chapter 9 - study notes

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Matthias Niemeier

Explain premotor theory of attention observation we unable to move our eyes wo shifting our attention but we can shift our attention wo moving our eyes. Cuz (not in book) shift of attention are oculmotor program, u shift your attention when ur oculmotor program is ready to be executed, it takes some time to process the activity. At that point when oculmotor program is ready to be executed so eye can be moved to target of interest that is the point when u move your eye. So attention perceives eye movement. So eye moves after shift of attention but that depends on if itz overt or covert attention, if it is overt then we do shift eye attention. Possible that itz covert of attention if we dont shift our eye. Itz possible cuz the oculmotor program might not be ready to executed so itz not passed on to muscle of eyes, so activity might not enter brain so no shift eye before attention. QUIZ 2) ILD = interaural level difference. CH9 HEARING: PHYSIOLOGY AND PSYCHOACOUSTICS WHAT IS A SOUND? Deafness deprives u of the most fundamental of human abilities: communication through speech Sound created when objects vibrate, vibration causes molecules in objects surrounding medium to vibrate which causes pressure to change in medium (for humans, usually earths atmosphere). Pressure changes can be described as waves; they are similar to waves on pond that are caused when we drop a rock into water. Water molecules displaced by rock not themselves travel very far, but the pattern of displacement will move outward from source until smt gets in itz way. Though pattern of sound and waves not change, the initial amount of pressure does change, it getz less prominent. Sound waves travel at a particular speed depending on medium, moving faster through denser substances, ie muggy days. Normally speed of sound through air is about 340ms. Light moves way faster. A jet plane travels faster than the speed of sound, ie plane catches up to and passes the fronts of sound waves it is creating. Thus sound waves combine into a shock wave, or a huge pressure fluctuation. When shock reaches ground, it makes a sound called sonic boom BASIC QUALITIES OF SOUND WAVES: FREQUENCY AND AMPLITUDE Sound waves that we hear are fluctuations in air pressure across time. Magnitude of pressure change in sound wave difference bw highest pressure area and lowest pressure are = amplitude (magnitude of displacement ie increase or decrease, of a sound pressure www.notesolution.comwaves or of a head movement, ie angular velocity, linear acceleration, tilt) or intensity (amount of sound energy falling on a unit area ie square centimetre) of a wave Pressure fluctuations can be very close together or they can be spread apart over longer periods. For light waves, we describe pattern of fluctuation by measuring distance b peaks in wavelengths. Although sound waves have wavelengths we describe its pattern by noting how quickly pressure fluctuates, rate of fluctuation = frequency of the waves = for sound, the # of times s that a pattern of pressure change repeats. Frequency is measure by hertz (Hz), 1 Hz equals 1 cycle s. For ex, 500Hz wave goes from its highest point down to its lowest point and back up to its highest point 500 times every s. Amplitude is associated w perceptual quality of loudness = psychological aspect of sound related to perceived intensity or magnitude, more intense = more loud. Frequency is associated w pitch = psychological aspect of sound related mainly to the fundamental frequency. Low frequency = low pitch, high = high. Humans hear across a wide range of sound intensities, ratio bw faintest sound that can be heard to loudest could be heard wo damage to ear is more than a million. sound levels are measured on a log scale using units called decibels (dB). dB define the diff bw 2 sounds as the ratio bw 2 sound pressures. Each 10:1 sound pressure ratio equals 20 db, and a 100:1 ratio equals 40 dB Equation for defining decibels dB=20log(ppo) small o. P=pressureintensity of sound. Po = reference pressure = 0.0002 dynecm2. And levels are defined as dB SPL (sound pressure level). 0.002 dynecm2 is a level close to the minimum pressure that can be detected at frequencies for which hearing is most sensitive, and dB values greater than 0 describe ratio bw a sound being measured and 0.0002 dynecm2 If the pressure of the sound you measuring (p) is equal to 0.0002 dynecm2, then dB = 20 log(1). Log (1) = 0, a sound pressure that low would be equal to 0 dB SPL For log scales such as dB, relatively small decibel changes can correspond to large physical changes. For ex, an increase in 6 dB corresponds to doubling of amount of pressure SINE WAVES, COMPLEX TONES, FOURIER ANALYSIS Sine wave pure tone = waveform for which variation as a function of time is a sine function = simplest kinds of sound. Air pressure in sine wave changes continuously (sinusoidally) at same frequency. Time taken from one complete cycle of a sine wave is period (time, or space required for one cycle of a repeating waveform) of the sine wave, and there are 360 degrees of phase (relative position in time of 2 or more sine waves) across one period. Sine wave is described in degree. www.notesolution.com
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