Auditory Perception

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What is sound frequency in terms of wavelength?

1/wavelength

What is the range of frequency that humans can hear?

30Hz-20kHz

What is the perceptual term for frequency?

Pitch

What is the units and perceptual term for amplitude?

Db and loudness

What is Timbre?

The superimposing of multiple different frequencies

What is the perceptual term for timbre?

complexity

What is the equation for calculating decibels, using air pressure of stimulus (P) and standard pressure of sound (P0)?

Db=20x Log(p/p0)

That equation rewritten is…

10 decibels is proportional to 2 times the perceived loudness

What is the name for the outer part of the ear?

The Pinna

After sound travels past the pinna and through the auditory canal what are the 3 small bone structures that send the signal to the inner ear?

Malleus (Hammer), Incus (Anvil) and Stapes (stirrup)

What is the main role of the 3 ossicle bones in the ear?

Converting air wave sound to fluid wave sound

What is the snail like structure of the inner ear?

Cochlea

What are the 3 main components of the cochlea

Basilar membrane, Techtorial membrane and hair cells

How does the basilar membrane accomodate for all frequencies of human sound?

The base is soft for lower frequencies and hard at the tip for higher frequencies

What is the term given to the basilar membranes ability to accommodate for all frequencies?

Tonotopic mapping

Outline transduction in the cochlea

Vibration of basilar membrane, Hair cells pull against techtorial membrane, movement of hair on cell opens sodium channel, action potential initiated

What is the issue with the transduction of frequencies above 1000Hz?

Neurons physical fire rate limit is at 1000Hz

How do the aural ganglion cells communicate frequencies above 1000Hz?

By transmitting where the frequency vibrates the basilar membrane, Place coding

How is loudness transduced for frequencies above 1000 Hz?

Rate of vibration of membrane conveys the amplitude, Rate coding

How are frequencies below 200 Hz transduced for pitch?

Rate coding

How are frequencies below 200 Hz transduced for loudness?

The number of hair cells active is transmitted to the ganglion cells

What is the term for left and right direction on the auditory field?

Azimuth

What are the 3 types of Azimuth cues used for auditory localisation?

Intensity, Time of onset and phase differences

Outline intensity differences

At 2000Hz the head will cast a sound shadow creating a sound intensity difference in each ear

Why does the the frequency of the sound have to be at least 2000hz to have the intensity difference?

At lower frequencies, the sound waves miss the head

Outline time of onset differences

Sound will reach each ear at a different time causing for a discrepancy

Outline phase differences

At 3000 Hz the eardrums will be in different positions when hearing a sound with a strong azimuth bias

Why does the frequency have to be at least 3000 Hz in order to have phase differences?

Wavelength will be larger than the width of the human head ear-ear, allowing for each ear to be in a different phase of the sound wave

Outline the monaural, spectral cue.

Sound direction can be perceived by how the waves reflect of the pinna into the ear canal