Hearing Flashcards
what is sound?
vibration of air molecules > a sequence of pressure waves which propagate through the elastic net of air.
what is loudness (in terms of vibrations)
it’s the oscillation amplitude, the higher the amplitude, the louder the sound
what is pitch?
It is the frequency, the faster the frequency the higher pitched the sound.
What is timbre?
It is the juxtaposition of pure tones, so it’s the complexity of sound
synonym for pure tone:
sinusoidal sound wave
What’s the frequency spectrum?
It captures sound oscillations and divides them into pure tones.
The two properties of the frequency spectrum: and what is the analysis called?
level: amplitude of the oscillation
spectrum: how many pure tones there is.
The analysis is called Fourier analysis.
What formes the outer ear?
From the outside ear lobe, to the ear drum.
middle ear:
contains the stapes, malleus and incus which amplify the sound and transmit this amplification to the oval window.
What is the sound bouncing off the body called?
Head-related transfer function (HRTF).
What’s the inner eat:
Contains the cochlea, the basilar membrane and the cell hairs. The inner eat transduces the mechanical signal into action potentials in the auditory nerve.
what is a tonotopic map? And what are the two frequencies … basilar membrane?
an orderly map of sound frequencies because each location on the basilar membrane responds best to one sound frequency only: best frequency and characteristic frequency
How is the basilar membrane formed and which frequencies are represented where?
It is large and stiff at the base and narrow and loose at the apex. High frequencies best at the base, and low at the apex.
How does the ear conduct a Fourier analysis?
As each sound corresponds to a different part of the basilar membrane, the inner ear breaks down complex sounds into frequencies that the sound is made of. This tonotopic representation is then transduced into neural signalling in the auditory nerve, which is also tonotopically organised.
What is place coding?
only those fibres of the auditory nerve that represent the frequency components present in the sound are activated
What is phase locking?
nerve fibres that are synchronised to the vibration of the basilar membrane
What is temporal coding?
Ot originates from phase-locking, which means that frequency is also represented through the timing of activity > sounds with higher frequencies produce higher rates of synchronized firing.
How many subcortical stations is there in the central auditory system and what are they?
- auditory nerve (AN)
- cochlear nuclei (CN)
- Superior olivary complex (SOC)
- Inferior culliculus (IC)
- MGN in the thalamus
- primary auditory cortex
What happens in the cochlear nuclei
The sound from the AN of both ears is combined and sound location is coded.
What happens in the Superior Olivary Complex?
Sound location is further processed.
What does the inferior culliculus do?
It seems to be a major interactive centre where pitch is extracted.
What happens in the MNG?
As part of the thalamus, it could be that it controls the attentional focus.
How do we mainly localise sound? And what does this produce (with help from what)?
Through cross-ear differences in sound wave amplitude and sound wave arrival. Implemented by the HRTF (the bouncing in the body) it creates a three-dimensional sound space surrounding us.
Main difference between auditory processing and visual processing
The visual system is far simples than the auditory one. It represents location and colour and creates a retinotopic map. The visual signal is multidimensional, in contrast sound signal at each ear is a one-dimensional time series of vibration and the signals are mixed. So the system has to be complex to make sense of it all.
