2The Nature of Sound Sound, like light, comes in waves Sound is vibrationFeatures of sound include:PitchHertzDecibels
3Pitch A sound’s highness or lowness Dependent on the frequency of the sound waveIs measured as hertz (Hz)High pitched soundsLow pitched sounds
4Hertz (Hz)A measure of the number of sound wave peaks per second; measures “frequency”Determines the pitch of the soundHuman hearing goes from 20 Hz to 20,000 Hz
5Frequency of Sound Waves The frequency of a sound wave is measured as the number of cycles per second (Hertz)20,000 Hz Highest Frequency we can hear4,186 Hz Highest note on a piano1,000 Hz Highest pitch of human voice100 Hz Lowest pitch of human voice27 Hz Lowest note on a piano
6Decibel (dB) A measure of the height of the sound wave Determines the loudness of the soundSometimes called amplitudeLoud soundsSoft sounds
8Above are examples of Frequency & Amplitude/decibels Who hits the higher pitch? Christina or Mariah?Discovering PSY p. 94 Figure 3.7Above are examples of Frequency & Amplitude/decibelsTimbre – distinctive quality of a sound determined by the complexity of the wave and its different combinations of frequencies. (Figure C is more complex than Figures A or B)
10Hearing: Sound WavesAuditory perception occurs when sound waves interact with the structures of the earAudition (sense of hearing) results in sound waves being collected in the outer ear, amplified in the middle ear and converted to neural messages in the inner ear.
11Purpose of the structures in the ear: Anatomy of EarPurpose of the structures in the ear:Measure the frequency (pitch) of sound wavesMeasure the amplitude (loudness) of sound waves
12Parts of the Ear – Sound Waves enter through the Pinna
17Auditory CanalSound Waves enter through the pinna then travel through the auditory canal.The opening through which sound waves travel as they move into the ear for processingEnds at the tympanic membrane (eardrum)
25Oval WindowThe point on the surface of the cochlea which receives the sound vibration from the ossiclesAs the oval window vibrates, the fluid in the cochlea vibrates moving hair cells along the basilar membrane.
26Hair cells along the Basilar Membrane move as the fluid vibrates
27Anatomy of the Cochlea Another View Outer earMiddle earInner earA sound causesthe basilarmembrane to waveup and down.BasilarmembraneHair cellsTectorialRound windowEardrumOval windowCochlea,partiallyuncoiledStirrupAnvilHammerSoundwavesAuditorycanal
28Hair CellsThe receptor cells for hearing in the cochlea that change sound vibrations into neural impulses. When they move they trigger action potential in the base of the hair cell (transduction).Similar to the rods and cones within the eye except hair cells are sensitive to vibrations rather than light.If these are damaged (due to prolonged loud noises) then you have nerve deafness which cannot be helped by a hearing aid.
30Auditory NerveThe nerve that carries sound information from the ears to the thalamus then to the auditory cortex in the temporal lobes of the brainThe auditory nerve is stimulated by the hair cells in the basilar membrane of the cochlea.
31Major Divisions of the Ear Outer Ear—acts as a funnel to direct sound waves towards inner structuresMiddle Ear—consists of three small bones (or ossicles) that amplify the soundInner Ear—contains the structures that actually transduce sound into neural response
35Anatomy of the Ear: A final look Hockenbury Powerpoint (schulman)
36Transduction of Sounds Sound waves are captured by the Pinna and sent down the ear canal where they stimulate the eardrum.The eardrum’s vibrations are amplified by the ossicles (hammer, anvil, stirrup).These vibrate the oval window on the cochlea which in turn vibrates the fluid around the basilar membrane.The fluid bends the hair cells on the basilar membrane triggering action potential in the base of the hair cells.This message is transmitted to the auditory nerve which carries the info to the thalamus and then to the auditory cortex of the temporal lobe.Review using this Nobel Prize site on Hearing
39Distinguishing PitchFrequency theory—basilar membrane vibrates at the same frequency as the sound wave/oval windowThe higher the frequency wave the faster the firing of hair cellsTheory used to explain how you hear low frequenciesPlace theory—different frequencies cause larger vibrations at different locations along the basilar membraneDifferent pitches stimulate different areas on the basilar membraneThe brain receives these messages and interprets them as different pitches.Theory used to explain how you hear high frequencies.Use both theories when you listen to sounds with both high and low frequencies. See this website to see how it works.
40Direction of traveling wave Frequency TheoryThe Basilar Membrane vibrates according to the same Frequency of the sound waveBasilarmembraneDistalendProximalOval windowDirection of traveling wave
41Place Theory: Different Frequencies stimulate different areas of the Basilar Membrane
42Coding and Auditory Masking The way in which waves travel down the Basilar Membrane causes some sounds to interfere with (or mask) our ability to hear other soundsLow frequency sounds provide better masking than high frequency sounds
43Auditory MaskingPiccolo, softBassoon, loudPiccolo, loudBassoon, softDistance along basilar membrane(a)(b)Effect of bassoon on basilar membraneVibrationamplitudeof basilarmembraneEffect of piccolo on basilar membraneLow frequency sounds effectively mask high frequency soundsHigh frequency sounds cannot effectively mask low frequency soundsHockenbury Powerpoint (schulman)