Textbook Notes (362,880)
Canada (158,081)
Psychology (1,877)
PS101 (450)
Chapter 4

ch.4 PartII.docx

7 Pages
Unlock Document

Wilfrid Laurier University
Mindi Foster

Our sense of Hearing: The Auditory System The Stimulus: Sound  Waves are vibration of molecules o travel through some physical medium, i.e. Air  Sound waves generated by vibrating objects o i.e. Guitar String, vocal cords, loudspeaker cone o i.e. forcing air past a chamber(pipe organ),suddenly releasing a burst of air when you clap  Characterized by Amplitude, Wavelength, Purity o physical property of A,W,P affect the perceived qualities of loudness, pitch, and timbre o physical property of sound interact in complex ways to produce perceptions of these sound qualities Physical properties of sound Related perceptions Amplitude Loudness Frequency Pitch Purity Timbre Human Hearing Capacities  Wavelengths of sound → frequency o frequency is measured in cycles per second, or hertz(Hz) o ↑frequencies, ↑pitch o the perception of pitch depends mainly on frequency, but also influenced by the amplitude of the sound waves  what people can hear – a portion of the available range of sounds o human hear (Low of 20Hz) ~ (High of 20 000Hz) o sensitivity to high-frequency tones declines as adults grow older o Low frequency sounds under 10Hz – homing pigeons o bats and porpoises – above 20 000Hz  ↑amplitude of sound waves, ↑sound perceived o amplitude is measured in decibels(dB) o perceived loudness doubles every 6-10 decibels o in work settings, chronic exposure to sounds above 85 decibels is considered risky and is strictly regulated o exposure to sound over 120 decibels → painful, damage to auditory system  Portable music players – over 100 decibels through headphones  The absolute thresholds for the weakest sounds people can hear differ for sounds of various frequencies. o Human ear is most sensitive at frequency near 2000Hz o Amplitude is the principal determinant of loudness, but loudness ultimately depends on an interaction between amplitude and frequency  Variations in the purity of sounds o Purest sound = only a single frequency of vibration, i.e. tuning fork o The purity or complexity of a sound influences how timbre is perceived o ex. a note with same loudness and pitch played on a horn and a violin→different timbre Sensory Processing in the Ear  Human ear 3 sections – external ear, middle ear, inner ear o external ear depends on the vibration of air molecules o middle ear depends on the vibration of movable bones o inner ear depends on waves in a fluid, which are finally converted in to a stream of neural signals sent to the brain o External ear consists of the Pinna, a sound-collecting cone  cut ur hand behind ur ear → augment the cone  sound waves collected by the pinna are funneled along the auditory canal toward the eardrum, a taut membrane that vibrates in response o In the Middle ear, the vibrations of the eardrum are transmitted inward by a mechanical chain made up of the 3 tiniest ones in your body (the hammer, anvil, and stirrup), known collectively as the ossicles.  The ossicles form a 3-stage lever system that converts large movements with little force into smaller motions with greater force  the ossicles serve to amplify tiny changes in air pressure o The Inner ear consists largely of cochlea, a fluid-filled, coiled tunnel that contains the receptors for hearing.  cochlea – a Greek word for a spiral-shelled snail, which this chamber resembles  Sound enters the cochlea through the oval window, which is vibrated by the ossicles  ear’s neural tissue = retina in the eye, lies within the cochlea. This tissue sits on the basilar membrane that divides the cochlea into upper and lower chambers  The basilar membrane, which runs the length of the spiraled cochlea, holds the auditory receptors. Auditory receptor is called hair cells.  Waves in the fluid of the inner ear stimulate the hair cells. Like the rods and cones in the eye, the hair cells convert this physical stimulation into neural impulses that are sent to the brain. o These signals are routed through the thalamus to the auditory cortex, which is located mostly in the temporal lobes of the brain. Auditory Perception: Theories of Hearing(pitch perception)  Place Theory-Helmholtz o Perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane. o Hair cells at various locations respond independently o different hair cells vibrated by different sound frequencies o Brain detects the frequency of a tone according to which area along the basilar membrane is most active  Frequency Theory o Perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates. o The whole membrane vibrates in unison in response to sounds. o Brain detects the frequency of a tone by the rate at which the auditory nerve fibres fire.  Reconciling (Place and Frequency Theories) o competition: reminiscent of the dispute between the trichromatic and opponent process theories of colour vision. o both turned out to be valid in part. o hair cells along the basilar membrane are NOT independent (place wrong, frequency right) o the wave peaks at a particular place depend on the frequency of the sound wave. (Place right) o Current Thinking: pitch perception depends both on place and frequency coding of vibrations along the basilar membrane. o Low frequency tones appear to be translated into pitch through frequency coding. Auditory Localizations: perceiving Sources of Sound  Auditory localization – locating the source of a sound in space  ①Intensity(loudness) + ②Timing of sounds arriving at each ear  Shadow, or partial sound barrier, cast by the head itself  Sounds can be localized by comparing the timing of their arrival at each ear  People can detect timing differences as small as 1/100 000 of a second Music and its Effects  the brains of musicians are identifiable and would be larger in areas(motor, auditory, visuospatial areas of the cerebellum) than the brains of nonmusicians  speech prosody – musical aspects of speech(intonation – melody, stress and timing - rhythm) Comparing Vision and Hearing Dimension Vision Hearing Stimulus Light waves Sound waves Wavelength/hue Frequency/pitch Elements of stimulus and related perceptions Amplitude/Brightness Amplitude/loudness Purity/saturation Purity/timbre Receptors Rods and cones Hair cells Location of receptors Retina Basilar membrane Main location of processing in brain Occipital lobe Temporal lobe visual cortex Auditory Cortex Spatial aspect of perception Depth perception Auditory Perce
More Less

Related notes for PS101

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.