Chapter 10 Flashcards
What are the first two auditory locailizaiton cues?
1)Sound pressure do not arrive at both ears at the same time, sounds arrive slightly sooner at the ear closer to the source
2)Intensity of a sound is greater at the ear closer to the source
Interaul Time Differences
Difference in time between arrivals of sound at one ear versus the other
Azimuth
Refers to the horizontal angle or direction from which a sound is coming, and it describes the left-right positioning of sound sources in relation to the listener.
Sound that comes from directly in front of or directly behind the head produces an ITD of ______ and reaches both ears ______
0; simultaneously
Medial Superior Olive
First place in the Auditory system where inputs from both ears converge,
Why do firing rates of neurons in the MSO increase in response to?
very brief time differences between inputs from the two ears
What are two different ways neurons in the medial superior olive (MSO) may detect time difference between two ears?
(A) Differences in the lengths of neural axons coming from the two ears were initially thought to provide time delay,
(B) more recent evidence suggests that the brain uses small differences in frequencies across the two ears, taking advantage of the time it takes for sound
Interval Level Difference (Second cue to sound localization)
Difference between levels (intensities) of sound at one ear versus the other
What is the main difference between ITD and ILD in terms of their effectiveness for sound localization?
The head blocks high-frequency sounds more effectively than low-frequency sounds due to the long wavelengths of low-frequency sounds “wrapping around” the head. This means that ILDs, which are are most effective for high-frequency sounds, but greatly reduced for low frequencies, becoming almost nonexistent below 1000 Hz.
Where are neurons that are sensitive to intensity differences between the two ears found?
Lateral Superior Olive
Lateral Superior Olive
Relay station in the brainstem where inputs from both receive both excitatory and inhibitory inputs.
Excitatory connections to each LSO come from the?
Ipsilateral ear
Where do excitatory connections originate from?
Excitatory connections to the left LSO originate in the left cochlea, and excitatory connections to the right LSO come from the right cochlea
Where do inhibitory inputs come from?
Contralateral ear (ear on the opposite side of the head)
Neurons in the LSO are very sensitive to differences in intensity across the two ears?
Because excitatory inputs from one ear (ipsilateral) and inhibitory inputs from the other ear (contralateral) are wired to compete
Cones of Confusion
A region of positions in space where all sounds to produce the same time and level intensity differences
The Directional Transfer Function:
A measure that describes how the pinna, ear canal, head and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space (azimuth and elevation)
How do relative intensities of different frequencies change depending on?
Depending on the direction of the sound source (azimuth) and changes in elevation of the sound source also affect the relative intensities of different frequencies.
What is the cue used for judging the distance of a sound source?
The relative intensity of the sound
Inverse square law:
The intensity of a sound drops very quickly with a greater distance of a sound source
Why does intensity works best as a distance cue when the sound or source of the listener is moving?
In the case of sound, when a sound source is closer to you, the change in direction of the sound seems more noticeable compared to when the sound source is farther away.
Waht is an important quality of a complex sound?
The way it begins (the attack of the sound) and ends (the sound’s decay)
Attack:
Part of sound during which amplitude increases
Decay
Part of sound during which amplitude decreases
Harmonic spectrum:
Collection of different frequencies or tones that make up a complex sound, such as a musical note or a sound wave, in a specific pattern or arrangement.
Fundamental Frequnecy:
Lowest frequency of a harmonic spectrum
What is the missing fundamental effect?
The missing fundamental effect refers to the perception of a fundamental frequency or pitch in a complex sound, even when the actual fundamental frequency is absent,
What is the auditory cue of the spectral composition of sounds analogous to?
Analogue to the visual depth cue of aerial perspective which involves the fact that more distant objects look more blurry
What happens to higher frequencies when sound travels through the air?
Higher frequencies lose more energy compared to lower frequencies due to the air’s sound-absorbing qualities, making the sound seem “muddier” or less “clear”
What is the final distance cue in understanding how far away a sound is?
The final distance cue is based on the fact that when we hear a sound, it’s a combination of direct energy (from the source) and reverberant energy (which bounces off surfaces in the environment). The relative amounts of direct versus reverberant energy inform us about distance.
How does the relative amounts of direct and reverberant energy inform the listener about distance?
When a sound source is close to a listener, most of the energy reaching the ear is direct, and reverberant energy is less prominent. However, when a sound source is far away, reverberant energy provides a greater proportion of the total sound reaching the ear compared to direct energy.
Why do these reverberations not decrease rapidly in intensity when the sound source gets closer or farther away?
The reverberations do not decrease rapidly because the surfaces that the sound bounces off of do not move.
What is the fundamental frequency attributed to?
This effect is attributed to the temporal code for sound frequency, where the brain interprets the pitch based on the timing or temporal patterns of the harmonics or overtones present in the sound.
