Perception chapter 2

When everyone loses hearing with age, what frequencies do we lose first?

We lose the upper frequencies of sound first 

What is the stimulus of the auditory system? and what type of energy is it?

Stimulus: sound waves(think ripples on a pond!)

• Move in circles from the source 

Sound waves are a type of mechanical energy

Vibrations cause changes in….

Pressure of the medium

Compression followed by expansion

In the auditory system, vibrations cause changes in the fluid pressure within the cochlea (and the movement of the basilar membrane and hair cells), which transform mechanical energy into electrical neural signals sent to the brain. 

what produces all sound waves?

a vibrating source

What is the wavelength of sound?

And what are sound waves?

?: linear distance between the same point on two successive waves(a cycle)

?: the compression and expansion of air molecules 

what is the frequncy and amplitude of sound waves?

?: the number of cycles completed per second(Hertz)

?: height of the wave 

What does wavelength+frequency=?

amplitude=?

wavelength+frequency=pitch 

Amplitude=loudness 

what is the phase of a wavelength?

The phase is the part of the cycle the wave is in 

This is important because the speakers at a concert must be aligned and in sync 

wavelength is inversely proportional to…

frequency

What does frequency mean practically, and what is it denoted by?

Number of cycles per second 

Denoted by Hertz(Hz, 1 cycle per second)

What is human sensitivity to frequency? what is it compared to other species like dolphins?

Human sensitivity is around 20 to 20,000 Hz, with substantial age and gender variability

Other species can detect sounds up to 150,000 Hz(dolphins, whales)  

What is resonance?

tendency for objects to vibrate at their natural frequency

frequency produces psychological attribute of…

pitch

what is the shape of the relationship between frequency and pitch? expect at extremes

linear

what is the Doppler effect?

The Doppler effect is the change in the frequency of a wave relative to an observer who is moving relative to the wave source

Perceived change in pitch as a function of changes in frequency and wavelength when either the wave source or the observer is moving

What is a bel?

?= common logarithm of the ratio between two sound energies (common reference point is the absolute threshold for human hearing; about 20 uPa (micro-pascals)

what is amplitude?

?: Amount of pressure displacement from rest. measured in bels or decibels(after alexander gramahm bel)  

What is the logarithmic scale of amplitude?

Reflecting our sensitivity to an extreme range of amplitude differences 

What is loudness a primary function of?

Primarily a function of intensity(amplitude)

• L = kP0.6 (Note exponent is less than 1. What does that mean???)

what are fletcher-Munson curves?

?: show how equal loudness is perceived for sounds of differing frequency and amplitude 

graphs showing that human hearing is not equally sensitive to all sound frequencies. We hear middle frequencies (2 to 5 kHz) best, while low bass and high treble require more volume to sound just as loud. At low volumes, bass and treble seem to disappear. 

What is perceived better? Low- and high-frequency sounds or sounds in the 1000-6000 Hz range??

Low and high-frequency sounds are not perceived as well as sounds in the 1000-6000 Hz range

This is what the loudness button on your receiver is for! The button tries to even out the curves 

a vibrating body produces…

A vibrating body produces waves of different phases and frequencies, so the resulting sound is a series of multiple waves 

what are harmonics?

?: Multiple of the lowest tone(the fundamental frequency or first harmonic)

what is the psychological attribute of timbre?

?: The character or quality of a musical sound or voice as distinct from pitch and intensity

The differences between guitar and piano

what is the complexity of sound perception?

Everything we hear is complex tones, tuning forks are the only things that produce single tones 

Simultaneous waves from either a single source or multiple sources

What are beats, and what do they reflect?

?: reflect phase, the part of the cycle a wave is in at any given moment

Steady, consistent pulse

what is masking?

More intense tone will reduce or eliminate the perception of the softer ton

What is constructive interference?

?: Waves line up in phase (crest meets crest, trough meets trough). Their amplitudes add together to make a bigger wave with higher intensity

What is destructive interference?

?: Waves line up out of phase by half a cycle (crest meets trough). Their amplitudes subtract, making a smaller wave or canceling out completely to zero.

what is the pinna?

?: The external fleshy covering on each sides of one’s head 

Acts as a funnel to catch sound waves and channel them into the ear 

Provides minor amplification of the signal 

As always, shaped by evolution to aid survival and reproduction

what is the external auditory canal?

?: About 1 inch long and 0.3 inches in diameter 

Conducts and channels vibrations to the middle ear 

Amplifies certain frequencies 

what is the tympanic membrane(eardrum)?

?: Vibrate at the same frequency as the waves coming in 

Thin, fibrous membrane, easily damaged 

Don't put things in your ear(including Q tips) 

Vibrates in resonance to sound wave coming through external auditory canal 

what is the ear’s only main defense against damage?

This is the ear’s only main defense against damage 

The eardrum can stiffen and retract if there are loud noises so they don't process sound as well 

what are the ossicles?

?: composed of three bones: malleus, incus, stapes

Receive and deliver vibrations (to the oval window of the cochlea) 

Can decrease amplification to protect against very intense sounds 

The ossicles can fuse or degenerate; a cause of conductive hearing loss.

They are replaceable 

what is the cochlea?

Where does transduction occur? 

Origin of the auditory nerve 

what is the cochlea filled with?

The cochlea is filled with fluid, when vibrations occur, it causes waves in water through the upper canal to the lower canal 

All of the hair respond to a specific tone, which is organized by pitch 

• So the lower part responds to high frequency sounds 

what are the names for the upper, lower, and middle canals?

Scala vestibuli—Upper canal 

Scala tympani—Lower canal

Scala media—Middle canal 

what is the organ of corti?

Critical structure 

Where all the sensory receptors are found

Sits on the basilar membrane 

Structure on the basilar membrane covered by the tectorial membrane

Contains columns of hair cells

• 3500 inner(transducers); 20,000 outer hair cells(amplifiers)

• Each hair cell has up to 300 cilia

• Over a million cilia total 

• Cilia are the sensory receptions  for audition 

Incoming sound waves to the inner ear cause….

Incoming sound waves causes the basilar membrane to rise, and the hair cells to contact the tectorial membrane 

The touch of the hair and the membrane causes the signal to fire 

Ideally, the hair cells gently contact the tectorial membrane 

what do intense signals do to the inner ear?

Intense signals may cause damage as the hair cells press too hard against the membrane

If the cilia break, you cannot replace them 

what generates the neural response in the hair cells?

contact

How is the organ of Corti organized tonotopically?

Similar frequencies are represented in adjacent regions 

Higher frequencies are closer to stapes 

Resulting nerve fibers are tuned to different frequencies 

The organ of corti can be stimulated by….

bone conduction

how do cochlear impacts work?

?: Replaces a damaged cochlea 

It has a speech processor, picks up sound and converts it to electrical signals 

The brain recognizes the signal 

What are the 4 steps of auditory transmission to the brain?

superior olive complex

inferior colliculus

MGN of thalamus

primary auditory cortex

what happens in the superior olive complex?

Vital for sound localization

First, we compare left and right ear input 

Responsible for localizing sounds 

Localization needs to be quick

what happens in the inferior colliculus?

Middle brain, sits below the superior colliculus  

Auditory reflexes

Automatic responses to sounds that come into your world 

What happens in the MGN of the thalamus?

MGN of thalamus—Sensory relay station

Where is the primary auditory cortex located and what happens there?

Located in the temporal lobe 

Each cell responds to one tone

Tonotopical representations 

Fundamental processing of pitch and loudness

receive and process basic sound information from the ears via the thalamus

what happens in the 2nd auditory cortex?

Surrounds the primary auditory cortex 

Aids in sound localization 

Analyzes complex combinations of sound

what is conduction hearing loss?

problems with signal transduction

what is the most common sensory loss

conduction hearing loss

what is Otitis externa?

external ear infection

swimmers ear

what is Otitis media?

Middle ear infection

Children are vulnerable

what is Otosclerosis?

?: abnormal bone growth

What is sensorineural hearing loss?

damages to the auditory nerve, PERMANENT  

What is tinnitus?

persistent ringing in ear(s) 

Old people, and people exposed to loud sounds are at risk 

what is prebycusis?

Age related changes, such as:

Hair cell loss, HBP, diabetes, medication effects, reduced elasticity, otosclerosis 

what is Ménière’s disease?

Meniere’s disease—profound damage to the ear, reflecting in disruptions in the ear and the vestibular system

Balance issues, special awareness 

what is place theory of pitch perception?

?: Argues that pitch perception depends on where the stimulation occurs(which neurons are firing) 

Sounds of different pitches stimulate different regions of basilar membrane 

Who proposed the place theory of pitch perception? how did von Bekesy edit it, and what is its problem?

Proposed by von Helmholtz; revised by von Bekesy 

“Traveling wave form”: von Békésy. The point of maximal stimulation is determined by frequency 

Problem: does not explain our ability to make precise pitch discrimination of sounds 

what is the frequency theory of pitch perception? what founded it?

?: This perception depends on neuronal firing rate, not which neurons are firing

Rutherford: Basilar membrane vibrates at a rate to match the original sound frequency 

Thus, the frequency of firing matches the original sound frequency

Example: the basilar membrane would vibrate 100 times per second for a 100 Hz sound, and hair cells would fire 100 times per second 

what is the problem with the frequency theory of pitch perception?

The major problem with the frequency theory of pitch perception is that individual neurons cannot fire fast enough to match high-frequency sound waves.

What is the Volley principle of the Frequency theory? Who revised it?

Major revision by Wever

Neurons work together to match the original frequency 

what is the duplex theory?

The place theory works best for higher frequencies 

The frequency theory works best for lower frequencies 

Both are correct!

what are monarual cues used for?

Monaural cues for localizing sounds

• Intensity differences as a function of distance 

• Pitch differences for approaching or receding objects(doppler) 

what are binaural cues used for?

Binaural cues for localizing cues  

• Interaural time differences 

• Interaural intensity differences 

• Interaural phase differences 

What is the major clue for determining location, and what is the absolute threshold?

The Difference in Time for a Sound to Reach Each Ear

Absolute threshold for detecting differences is about 10 microseconds (a microsecond equals 1/millionth of a second)

Where are interaural time cues processed?

Processed by the Medial Superior Olive (MSO) of the Superior Olivary Complex

When you are facing forward, either behind or in front, you cannot localize 

how does amplitude differences connect to localizing sound?

Amplitude differences in sound going to each ear

Head can also act as a “sound shadow” for high frequency waves

how do phase differences connect to localizing sound?

Phase differences when a sound comes from one side 

Phase differences mostly occur for low-frequency waves 

what is the cone of confusion?

?: Interaural time differences are the same for points on the cone 

Sound is always the same distance farther from one ear then the other 

Can detect side, but not precise location 

Tilting Head in Any Dimension Changes Interaural Relationship for Time, Amplitude, and Phase Differences

Behavioral adjustments improve sound reception and localization for Distance and for Direction

what are reverberations?

?: Reflected sounds that come off surfaces in listening space

Consequences for sound

• Full and rich(if done right) 

• Muddy and vague if no 

Major concerns for architectural acoustics and sound engineers

how does time affect reverberations?

Ideal depends on the size of the listening space

RT under .3s are absorbed into the direct sound

Too Lengthy Produces “Muddy” Sound.

what are semantics?

Elements which convey meaning

what is syntax?

?: Specific rules of expression in a highly structured system(grammar) 

what is symbolic(displacement)?

communication about things that are not physically present 

What is generativity? What is the arbitrariness of symbols?

?: capacity for infinite expression 

?: use of non-connotative symbols 

What is a phoneme vs. a morpheme?

Phoneme:

• Individual speech sound

• English has 44(phonemes)(20 vowels and 24 consonants)

• Other languages have 20-60 

Morpheme:

• Smallest meaningful unit of language; can be prefixes, suffixes, or words 

How do we process phonemes?

Each phoneme has distinctive features of production

We possess an auditory template(featured detector) for each phoneme  

• Learned in the first year of life 

Phonemic boundaries; no blending, but shifting 

how is speech produced? what is the differences in vowels and consonants in terms of how we produce them?

Speech is produced by air flowing through the vocal tract

Vowel: opening air flow tract  

Consonant: closing air flow tract 

what is the place of articulation?

What is the manner of articulation?

?: point of obstruction 

?: How the block is produced (stop, nasal, etc.)

what is bottom up vs. top down processing of speech?

Bottom-up processing • acoustical information of phonemes 

Top-down processing • conversational context 

• Environmental context 

• lip/mouth movements 

• Non-speech cues

• Emotional content and inflections(functions of right hemisphere) 

What is Broca’s area? And what happens if this area is damaged?

Broca’s area: involved in language production(frontal lobe) 

Damage to Broca’s area leads to difficulty in producing speech(putting words together in sentences or even speaking single words)

What is Wernicke’s area? And what happens if this area is damaged?

Wernicke’s area: involved in language comprehension(temporal tobe)

Damage to Wernicke’s area leads to difficulty comprehending speech and producing coherent speech(not easily monitoring one’s own speech to make sure it makes sense) 

what is Aphasia?

an impairment in the ability to produce and understand language, usually caused by damage to the brain  wa

what is the McGurk effect?

?:perceptual illusion where visual cues (like lip movements) conflict with auditory cues (like spoken sounds), causing the brain to blend them into a third, unique percept

Speech perception involves visual cues 

Visual stimuli(lip movements) can influence speech perception 

Cross-modal integration of auditory and visual stimuli

Occurs mostly for phonemes, not words  

What is the phonemic restoration effect?

?: We use context to fill in missing phonemes 

We can eliminate up to half of the speech signal with little effect on perception 

Very common example of closure(filling in missing information)

what are speech boundaries(Segmentations)?

Speech is a continuous stream(no obvious breaks or markers)

We(as perceivers) must add the speech breaks(segmentation) 

This is why we think foreign languages sound faster(we lack the ability to break the sound up into discrete words) 

All languages are around 125 to 175 words per minute

When playing a note, what does the resulting pitch depend on?

The resulting pitch depends upon length of vibrating body

Creates a fundamental frequency an accompanying harmonics(multiple of the original frequency)

Different instruments produce differ harmonics 

what is music, like all sound, organized by?

pitch

what does pitch depend on?

Pitch depends upon length of the vibrating body 

Higher tone in pitch→smaller string 

doubling (or halving) the length produce psychologically similar sounds 

• Doubling the length will produce a sound one octave lower (deeper).

• Halving the length will produce a sound one octave higher

what is an octave?

?: A series of eight notes (A, B, C, D, E,F G) occupying the interval between two sound frequencies having a ratio of 2:1 (one having twice or half the frequency of the other). The 12 semitones (half-tones), 7 Tones plus C#, D#, F#, G# A#.

what is tone height vs tone chroma?

?:Increases in Pitch with Increasing Frequency(the perceptual quality of how "high" or "low" a sound is, corresponding directly to its fundamental frequency in hertz (Hz)

?: Psychological similarity of sound occupying the same relative position ondifferent octaves(a psychological and musical concept that refers to the perceptual quality allowing us to recognize the identity of a musical note (such as C, D, or A) independent of its octave)

language is to phonemes as…

Music is to notes as…

what are chords?

three or more notes played simultaneously

what is melody?

Linear arrangement of notes played in succession   

what does the ratio of notes mean?

Ratio of the difference between frequencies of notes(interval) determines perceptual pleasantness 

what is consonance vs. dissonance?

Consonance: simple ratios, most pleasing is 3/2(“perfect fifth”) 

Dissonance: more complex or less elegant ratios  

what is harmony?

?: Individual notes, melodies, or chords played simultaneously (by multiple sources)