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Sensory Systems: Auditory

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Sensory Systems : Auditory What do ... pathway is complex and involves several stations along the way to the auditory cortex in the brain Lots of processing ... – PowerPoint PPT presentation

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Title: Sensory Systems: Auditory


1
Sensory Systems Auditory
2
What do we hear?
  • Sound is a compression wave

Speaker
Air Molecules
When speaker is stationary, the air is uniformly
dense
3
What do we hear?
  • Sound is a compression wave

Speaker
When the speaker moves, it compresses the air in
front of it.
4
What do we hear?
  • Sound is a compression wave

Rarefaction
Compression
The speaker moves back leaving an area with less
air behind - called rarefaction
5
What do we hear?
  • Sound is a compression wave

Compression
Speaker
Rarefaction
The speaker moves forward again starting the next
wave
6
What do we hear?
  • Sound is a compression wave - it only looks
    like a wave if we plot air pressure against time

Air Pressure
Time
7
Properties of a Sound Wave
  • 1. Amplitude difference in air pressure between
    compression and rarefaction (Sound Pressure
    Level)

8
Properties of a Sound Wave
  • 1. Amplitude difference in air pressure between
    compression and rarefaction (Sound Pressure
    Level)
  • What is the perception that goes along with the
    sensation of sound amplitude?

9
Properties of a Sound Wave
  • 1. Amplitude difference in air pressure between
    compression and rarefaction (Sound Pressure
    Level)
  • What is the perception that goes along with the
    sensation of sound amplitude?

LOUDNESS
10
Properties of a Sound Wave
  • 2. Frequency how many regions of compression
    (or rarefaction) pass by a given point per second
    (expressed in Hertz)

11
Properties of a Sound Wave
  • 2. Frequency how many regions of compression
    (or rarefaction) pass by a given point per second
    (expressed in Hertz)
  • What is the perception that goes along with the
    sensation of frequency?

12
Properties of a Sound Wave
  • 2. Frequency how many regions of compression
    (or rarefaction) pass by a given point per second
    (expressed in Hertz)
  • What is the perception that goes along with the
    sensation of frequency?

PITCH
13
Sensing Vibrations
14
Sensing Vibrations
  • Outer ear transmits and modifies sound (critical
    for sound localization)

15
Sensing Vibrations
  • Middle ear turns compression waves into
    mechanical motion

oval window
stapes
16
Sensing Vibrations
  • Middle ear turns compression waves into
    mechanical motion

Oval window
Ear Drum
17
Sensing Vibrations
  • Middle ear turns compression waves into
    mechanical motion

Oval window
Ear Drum
Compression Wave
18
Sensing Vibrations
  • The cochlea, in the inner ear, is a curled up
    tube filled with fluid.

Auditory Nerve to Brain
19
Sensing Vibrations
  • Inside the cochlea is the basilar membrane
  • Movement of the oval window causes ripples on the
    basilar membrane

20
Sensing Vibrations
  • Basilar membrane measures the amplitude and
    frequency of sound waves
  • amplitude (loudness)
  • frequency (pitch)

21
Sensing Vibrations
  • Basilar membrane measures the amplitude and
    frequency of sound waves
  • amplitude (loudness) - magnitude of displacement
    of the basilar membrane
  • frequency (pitch)

22
Sensing Vibrations
  • Basilar membrane measures the amplitude and
    frequency of sound waves
  • amplitude (loudness) - magnitude of displacement
    of the basilar membrane
  • frequency (pitch) - frequency and location of
    displacements of the basilar membrane

23
Sensing Vibrations
  • Basilar membrane measures the amplitude and
    frequency of sound waves
  • frequency (pitch) - frequency and location of
    displacements of the basilar membrane

24
Sensing Vibrations
  • Bundles of hair cells are embedded in basilar
    membrane

25
Sensing Vibrations
  • When hair cells sway back and forth, they let
    ions inside
  • This flow of charges is converted to action
    potentials and sent along the auditory pathway

26
The Auditory Pathway
  • The auditory pathway is complex and involves
    several stations along the way to the auditory
    cortex in the brain
  • Lots of processing must be done in real-time on
    auditory signals!

27
How Can You Localize Sound?
  • Ponder this
  • Imagine digging two trenches in the sand beside a
    lake so that water can flow into them. Now
    imagine hanging a piece of cloth in the water in
    each trench. Your job is to determine the number
    and location and type of every fish, duck,
    person, boat, etc. simply by examining the motion
    of the cloth. Thats what your auditory system
    does!

- Al Bregman
28
How do we Stay Balanced?
  • The Vestibular System

29
Vestibular System (Balance)
30
Vestibular System (Balance)
31
Vestibular System (Balance)
32
Vestibular System (Balance)
Head accelerates this way
Fluid goes this way
Cupula gets pushed
33
Vestibular System (Balance)
Fluid goes this way
Head accelerates this way
Cupula gets pushed
34
Vestibular System (Balance)
  • movement of the cupula is detected by hair cells
  • hair cells in the vestibular system are more
    sensitive than hair cells on the basilar membrane!

35
Vestibular, Visual, and Proprioceptive Systems
Work Together
  • Try standing on one foot with your eyes closed!

36
Fun Facts about The Vestibular System
  • Seasickness arises when the vestibular system and
    the visual system send conflicting information

37
Fun Facts about The Vestibular System
  • Seasickness arises when the vestibular system and
    the visual system send conflicting information
  • People can be knocked down by moving walls!

38
Fun Facts about The Vestibular System
  • Seasickness arises when the vestibular system and
    the visual system send conflicting information
  • People can be knocked down by moving walls!
  • Alcohol causes the spins by (among other things)
    changing the density of the fluid in the
    semicircular canals

39
Hearing
  • Detection
  • Loudness
  • Localization
  • Music
  • Speech

40
Detection and Loudness
  • Sound level is measured in decibels (dB) - a
    measure of the amplitude of air pressure
    fluctuations

41
Detection and Loudness
  • Sound level is measured in decibels (dB) - a
    measure of the amplitude of air pressure
    fluctuations
  • dB is a log scale - 1 dB difference 10 times
    the actual air pressure

42
Detection and Loudness
  • Sound level is measured in decibels (dB) - a
    measure of the amplitude of air pressure
    fluctuations
  • dB is a log scale - 1 dB difference 10 times
    the actual air pressure
  • We have a dynamic range that is a factor of 7.5
    million!

43
Detection and Loudness
  • minimum sound level necessary to be heard is the
    detection threshold

44
Detection and Loudness
  • detection threshold depends on frequency of
    sound
  • very high and very low frequencies must have more
    energy (higher dB) to be heard
  • greatest sensitivity (lowest detection threshold)
    is between 1000 hz to 5000hz

45
Detection and Loudness
  • Detection can be compromised by a masking sound
  • even masking sounds that are not simultaneous
    with the target can cause masking (forward and
    backward masking)
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