Sven-hearing

Question 1

Why study hearing

Answer 1

Basis to speech and music, first thing in preg- 2 months before birth. Used for telecommunications, entertainment and auditory alerts. Mimic human behaviour with automatic speech recognised (Alexa). Help those W hearing aids/cochlear implants

Question 2

What hearing is used for

Answer 2

Who/what’s the source, where’s the source located. What direction is the sound moving, what info is the source sending

Question 3

What is sound

Answer 3

Arises from the movement/vibration of an object. Movement alternately squeezes air molecules together and pulls them apart. This pressure wave spreads outward from source to listener

Question 4

Define amplitude, period and pitch

Answer 4

Amp is loudness (the rise from starting). Period is the duration of a cycle in ms/s called frequency and perceived as pitch- expressed in Hz (number of times a period is repeated every second e.g. 5ms period has freq of 200hz). Sound can be a wave from or a spectrum (a bar chart W lines)

Question 5

The 3 attributes of sound and define timbre

Answer 5

Amp, freq and timbre. Timbre is also complexity is is when two sound that should sound the same are different

Question 6

In depth description of amp

Answer 6

Also known as the loudness. Measured in micro pascals (hearing threshold of 20, pain of 200000000) too big so use dB from 0(hearing threshold) to 140 (pain threshold). Loudness is the attribute of auditory sensation in terms of which sounds can be ordered on a scale from quiet to loud. As amp increases, waves get bigger and higher

Question 7

In depth description of pitch

Answer 7

Definition: attribute of auditory sensation in terms of which sounds can be ordered on a musical scale
As pitch increases, the waves get closer together but dont get higher

Question 8

In depth description of timbre

Answer 8

The attribute of auditory sensation in terms of which a listener can judge that two sounds similarly presented and having the same loudness and pitch are dissimilar (the quality/complexity of a sound). Similar in freq and amp

Question 9

Timbre- diff between pure and complex tones

Answer 9

To have timbre, a sound must have more than one freq. harmonic complex tones are multiples of a fundamental frequent (wave form not regular). Pure tones have one freq. Fundamental freq is the lowest of a harmonic and the second harmonic is double the fundamental freq. timbre is a modulator/equaliser as evens frequencies

Question 10

Speech

Answer 10

Starts W the rate of the vocal cords/larynx vibrating. There is then modulation by the vocal tract (lips, mouth..) so can have the same sound spectrum but W different sounds (leads to a spectrum of resonances from lips).

Question 11

Diff between waveform and plectrum

Answer 11

Waveform plots intensity over time and spectrum plots pitch and amp

Question 12

Structure of the ear

Answer 12

Outer ear (the ear flap) used for sound localisation as folds amplify frequencies, also has ear canal and the bone. Middle ear: estachian tube is an air filled cavity that connects W throat and has the eardrum, hammer, anvil, stirrup which make up the ossicles, the oval window and round window (makes pressure equal between ear and world, illness or flying means not equalised to eardrum bulges) cochlear and auditory nerve above

Question 13

Middle ear bones

Answer 13

Hammer, anvil and stirrup (stapes). The bones are attached to each other as vibrations hit eardrum which vibrates, the bones amplify vibrations so they hit the fluid filled cochlear (harder to vibrate in water). Stirrup is the one attached to the cochlear as it pushes against the oval window

Question 14

Stapedial reflex

Answer 14

Involuntary muscle contraction in the middle ear in response to loud sounds 10-20db below pain threshold.
Muscles stiffen the ossicular chain, pulling the stirrup/stapes away from the oval window
This is an auditory reflex and prevents damage to the cochlea

Question 15

The cochlea

Answer 15

Small and delicate, made of bone and fluid filled, coiled shape. Acts as freq analyser/converts energy at diff freq into neural activity in diff fibres of the auditory nerve. Vibrations at the oval window are passed along the top half (scala vestibuli) then the bottom half (scala tympani). Pressure released through the round window. Membrane separating chambers is the basilar membrane (narrow and stiff at the base but wide and floppy at the apex). Base vibrates with high freq sounds and apex at low freq. membrane vibrates when stirrup moves the fluid in the inner ear at at diff points depending on freq

Question 16

The organ of corti

Answer 16

Sits on the basilar membrane (gelatinous). Full of neurones, one row is inner hair cells (round and fat) and 3 rows out hair cells (long and thin, v shaped). Outer hair cells out energy back into the basilar membrane (amplify the basilar membrane)-without makes it harder to detect sound leads to detection failure/reduced loudness. Inner detect movement of the basilar membrane

Question 17

Action of the inner hair cells after detection

Answer 17

Rub against the tectorial membrane (above corti), triggering an ap in the neural fibre. Inner hair cells fire in synchrony W peaks in the waveforms of tines-aggregated over many fibres, time intervals between spikes show period of a stim

Question 18

Tuning curves

Answer 18

Each auditory nerve fibre only responds to a narrow range of frqs, reflects tuning of the basilar membrane at pace which excites the fibre. Tuning curve on a graph W tone freq against relative level of tone db (plots locations of aps). Many overlapping single fibre tuning curves in the nerve, patterns confirm cochlea acts as a freq analyser/freq selective

Question 19

Links

Answer 19

Freq/pitch of a tone coded by which fibres active in auditory nerve and when. Timbre coded by which combo of fibres active. Fibres W low low threshold detect low amps and can’t distinguish between medium and high, high spontaneous rate and narrow dynamic/db range (opposite for high). Intensity is coded by how quickly fibres are activated, loudness if total of neural activity

Question 20

Rest of the auditory nervous system

Answer 20

Cochlear nucleus is a relay station as sends neural activity to other nuclei in the brain stem (last level where ears are independent). Superior olive analyses location of source-earlier in ascending auditory system as needs precise timing. Inferior colliculus and medial geniculate analyse the pitch early in AAS as relies on precise timing. Primary auditory area in cerebral cortex analyses higher order features like spectral shape, layer as less reliant on T

Question 21

The cortex

Answer 21

The primary, secondary and associative cortex are in the temp lobe
Sounds are interpreted here
Auditory association cortex has wernickes area

Question 22

Frequency selectivity

Answer 22

Ability to separate sounds W diff frequencies that occur at the same time. Laser interferometry measures basilar membrane speed of movement (glass bead attaches and laser shines to see movement-surgically on animals) velocity of membrane depends on tone freq- louder perceived as lower freq and less specific and vice verda

Question 23

Tuning of auditory nerve

Answer 23

Insert micro electrode in auditory nerve. Each nerve fibre responds to narrow range of freqs. Show a reduction and shift of freq specifics as freq increases (in low freqs, won’t respond much and as increases, fires in a small range),

Question 24

Selectivity in real life

Answer 24

Ask ppl if they can’t tell the diff between two tones through headphones in silent booth. Resolved is when a noise is separate from another. Psychophysical tuning curves show the closer to the marker is in freq to the test tone, the lower the level of the asker is needed to mask the test tone. Masker adjusted until prevents the listener from detecting test (plots v shape)

Question 25

Perception using spectrogram

Answer 25

Plots frequency vs time. Fricative sounds (S,sh,z) easy to spot as seen at high freqs. High also at formants in vowels (vowels determined by freq of formants)

Question 26

Production of vowels

Answer 26

. Cue that distunguishes vowels are freqs of first 2 formants. A formant is more than one freq that have a peak of energy (it is each peak in a spectrum). First harmonic is the same as the fundamental freq

Question 27

Top down effect: ganong

Answer 27

1980- ambiguous phonemes. Create continuum between g and k, ps need to decide if they hear g or k- find categorisation curve (hear g, say g, between is between). If you add speech onto end like vids and kiss you get more k responses and same for gift and kilt-more g . Tendency to real world (lexical knowledge)

Question 28

Top down: Restoration effect

Answer 28

Warran 1970- play white noise in place of a letter, the brain fills it in e.g. approximate y due to lexical knowledge. Also find context effects cough during start of ‘eel, either eel was on the table or on the shoe and hear meal or heel (due to semantic knowledge

Question 29

Top down- sound and word reduction

Answer 29

In connected (conversation) speech, words are acoustically reduced (speek quicker). On its own, don’t recognise reduced speech but with context you can - due to syntactic and semantic knowledge

Question 30

Top down: mcgurk effect

Answer 30

Play a syllable, hear diff things based on a person’s lip movements.E.g. hear ba but hear fa or ba depending on person’s lips
Origin is articulatory knowledge: due to visual info or due to what you know it takes to create a sound with your mouth

Question 31

Top down: sine wave speech

Answer 31

Speech signal where the formants of speech have been replaced w pure tones tracking the intensity modulations of those formants over time-Distorted speech, can hear it after knowing what the sentence is.What ppl w cochlear implant hear
Origin: phonological, lexical, syntactic, semantic knowledge, fast recalibration

Question 32

Biology of top down connections

Answer 32

Little evidence for top down effects on lower level neural regions, mostly take place at cortical level but beyond auditory area (smg, stg, ifg) selective attention affects speech perception in brain stem (inattentional deaf ess-harder task, less hearing). Top down connection from superior olive to cochlea during selective attention (sharpen response of hair cells to detect tones), also the reflex. Top down don’t create auditory hallucinations, subcortical for selective attention but mostly cortical