LECTURE SEVEN Flashcards
SOUND
Waves of changing air pressure with compressions and rarefactions
* Simplest sound wave is a sine wave
FREQUENCY (Hz)
related to perceived pitch
AMPLITUDE (dB)
related to perceived loudness
FUNDAMENTAL FREQUENCY
- Basic determiner of pitch
- Sine waves have only one frequency, the
fundamental
HARMONICS
Changes the sound without changing its fundamental frequency (pitch)
* Complex tones have multiple frequencies at once
* For single vibration source, multiples of fundamental
* Harmonic spectra
* Gives sounds different timbre
TIMBRE
Independent of pitch and intensity
WAVEFORM
Intensity over time
SPECTOGRAM
- Frequency and intensity over time
- Benefit – can see all the frequencies that make up a sound
- Simple tones = One frequency gives One line on spectrogram
COMPLEX TONES
Multiple frequencies at once
* Many lines on spectrogram
HAIR CELLS
- Specialized neurons – auditory equivalent of photoreceptors
- Basilar vibration (from sound) leads to stereocilia
“hairs” flattening causing depolarization - Area of most vibration depends on frequency of
sound
THE COCHLEA
“Acoustic prism”
* Different areas respond most strongly to certain
frequencies
* Physical structure mirrors spectrogram seen earlier –
detects all frequencies in complex wave in parallel
* High frequencies stimulate hair cells near base, low
frequencies stimulate hair cells near apex
AUDITORY CORTEX
- Temporal lobe
- After A1, splits into dorsal (where) and ventral
(what) stream, just like vision
COCHLEAR IMPLANTS
Cochlea transmits electrical impulses to auditory cortex
* These impulses can also be provided artificially
HEARING LOSS
Conductive hearing loss
* Vibrations inhibited due to earwax buildup, infection, or otosclerosis
* Sensorineural hearing loss: Metabolic or Sensory
SOUND LOCALIZATION
Binaural and Monaural Cues
METABOLIC HEARING LOSS
Can be caused by certain drugs (ototoxicity)
SENSORY HEARING LOSS
Cause by exposure to loud noises over long periods of time
BINAURAL CUES
Interaural Time Difference (ITD)
– sound reaching opposite ear is delayed
* Interaural Level Difference (ILD)
– sound reaching opposite ear is quieter
MONAURAL CUE
Pinna folds – shape of ear
CONE OF CONFUSION
- Elevation and 3d make things trickier
- ITD and ILD are ambiguous for corresponding points
on the cone of confusion - Pinna cues can help
- Best way to resolve CoC? Move your head!
LOCALIZING DISTANCE
- Best at around 1 meter
- Underestimate long distances – inverse square law
- Really good at telling if things are approaching or
receding – change in intensity
REVERBERATION
Sound bounces off surfaces
* “Echo” occurs when distance is large with a lot of reflections
* Overall sound sensation combination of direct sound
and reverberations
* Reverb helps gauge how far away sound source is – ratio of direct to indirect sound
* Reverberations allow you to gauge size/shape of room as well as material of walls
AUDITORY STREAM SEGMENTATION
- Sounds in the environment are all mixed together
- Need to segment one “stream” (one source) of sound
from others - Auditory scene analysis
AUDITORY GROUPING PRINCIPLES
- Similar to Gestalt visual grouping principles
- Proximity (in time)
- Pitch
- Timbre
CONTINUITY AND RESTORATION
- Web activity
- When noise added to a sound – we can reconstruct
missing tones! - Prediction, top-down effects, etc.
AUDITORY ATTENTION
Ability to focus attention on one speaker alone when lots of other speakers as background noise
* Note – auditory cortex responds in almost the same way as listening to only one speaker (fMRI)!
* Acoustic startle response – VERY rapid motor response to a loud unexpected noise
* Probably a good idea
SIZE AND PITCH
- Pitch is a good determiner of the size of an animal
- If an unknown animal has a low pitch, it is probably
large – and should be avoided - Frog croaking is intentionally misleading!
Music Perception
- Music involves more complicated forms than
simple auditory perception - Tone / pitch
- Timbre
- Rhythm
- Language (if lyrical)
- Emotional content /
aesthetics - Music is perceived
holistically
AMUSIA
- Inability to perceive / reproduce tone
- “Tone deafness”
- Can be acquired or congenital
- Flipside – absolute/perfect pitch
MUSIC AGNOSIA
- Inability to perceive music holistically
- Similar to associative object agnosia – and similar locations of damage (temporal lobe, ventral stream)
- You can hear it as sound, but you can’t hear it as music
- Can appear selective to music – implications?
RHYTHM
- People can pick up on basic rhythm (pulse) of a song within only a few beats
- Neural entrainment
NEURAL ENTRAINMENT
Repetitive beat creates pulses of neural firing,
resulting in synchronized oscillations generated after only a few cycles
ENTRAINMENT AND BEAT
- Steady beat results in neural entrainment
- Different rates of beats have different effects
- Can result in altered states of consciousness
- Shamanic drumming: 4 – 4.5 beats per second
(Hz). Same frequency as theta brain waves (in between
wakefulness and sleep). Induces trance-like state
RHYTHM AND MOVEMENT
- When listening to rhythmic music, areas of motor
cortex and cerebellum are engaged - Rhythm perception is sensorimotor
- Entrain body movement to musical rhythm. Eg:Foot tapping, head bobbing, Dancing
MUSIC AESTHETIC
- The “beautiful” and artistic qualities of music (and art in general) are known as aesthetics
- Understanding aesthetics requires understanding of
psychological processes leading to “aesthetic experience” - Related to emotional aspects, but distinct
FEAR-SUPPRESSION AND AESTHETIC
- Music and fear-suppression (Huron)
- Something happens in the song that triggers a fear response (in the amygdala)
- Loud unexpected noises
- Crescendos
- “Bass drops”
- Frisson response
- We then appraise the initial fear response as not harmful
- This resolution of fear feels good, leading to part of the aesthetic experience
PREDICTION, MUSIC AND REWARD
- Caudate active during “anticipation”
- Nucleus accumbens (dopaminergic structure in
reward circuit) active during “peak” moments - Cycle of anticipation -> resolution is rewarding
- EDM break/build/drop structure
URBAN LEGEND MOZART
- “Mozart effect”
- Listening to Mozart before a test of. spatial reasoning improved scores on the test compared to control!
(Rauscher et al., 1993) - (as filtered by pop journalism) Mozart makes you smart!
MOZART EFFECT TRUTH
- Effect size was very small, and transient (doesn’t
last long) - Effect did not generalize to fluid intelligence
- NO evidence that it does anything to babies
- Effect can be seen with other stimuli…
- Other kinds of music also work (even heavy metal…if
you’re into it) - Pop music works better
- Stephen King fans get the same effect from listening to Stephen King
MUSIC AND CONGITIVE ABILITY
- Linguistic/attentional factors
- Don’t listen to lyrical music while reading
- Cognitive arousal is good…in moderation
- Listen to something you like, but not too much (distracting)
- Mostly instrumental, not too arousing, steady beat but not to the point of trance induction
