5) Audition II

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Questions and Answers

What is primarily compared to determine the location of a sound in the azimuth plane?

Monaural cues from one ear

Sound amplitude variation

Sound frequency differences

Interaural time differences (ITDs) (correct)

Which of the following factors can influence the range of interaural time differences (ITDs)?

Shape of the cochlea

Intensity of the sound source

Frequency of the sound

Distance between the two ears (correct)

How do monaural cues assist in sound localization?

By comparing signals from both ears

By identifying sound intensity and reverberation (correct)

By estimating distance based on sound frequency

By interpreting vibrations in the cochlea

What does the auditory system rely on to determine the elevation of a sound?

Only monaural cues Signup and view all the answers

What occurs when the sound source is straight ahead in relation to interaural time differences (ITDs)?

The sound reaches both ears simultaneously Signup and view all the answers

What is the typical maximum interaural time difference (ITD) encountered in humans?

600μs Signup and view all the answers

Which statement correctly contrasts the information obtained from vision and audition regarding object location?

Visual information is contained in the retinal image, while auditory information lacks physical location cues. Signup and view all the answers

Which cue is critical for determining the distance of a sound source?

Reverberation and intensity cues Signup and view all the answers

What primarily influences the interaural level differences (ILDs) that occur due to the location of the sound source?

The frequency of the sound Signup and view all the answers

Which part of the brainstem is involved in processing interaural time differences (ITDs)?

Superior olivary complex Signup and view all the answers

What are the primary binaural localization cues that provide information about sound azimuth?

Interaural time differences and interaural level differences Signup and view all the answers

What characteristic of sound sources makes it difficult to determine their elevation?

Ambiguous interaural level differences Signup and view all the answers

What happens to the sound intensity as the distance from the sound source increases?

Sound intensity decreases Signup and view all the answers

How do the lateral superior olive (LSO) and medial superior olive (MSO) differ in function?

LSO processes interaural level differences; MSO processes interaural time differences Signup and view all the answers

What term describes the set of points that produce identical ITDs and ILDs, causing localization confusion?

Cone of confusion Signup and view all the answers

What effect on localization does altering the shape of a person's external ear have?

Impairs the ability to localize sound elevation Signup and view all the answers

What is reverberation, in relation to sound distance perception?

It encompasses how sound reflects off objects Signup and view all the answers

For which type of sound does phase-locking tend to be most helpful?

Low frequency or abrupt-onset sounds Signup and view all the answers

Study Notes

Cognitive Psychology 1 - Audition II

Auditory Scene Analysis: The challenge of separating sounds from multiple sources in a complex auditory environment.

Learning Objectives

Describe the cues used to determine the location of a sound source.
Understand the basic principles of auditory grouping that help us to make sense of the auditory scene.

Sound Localisation

Visual vs. Auditory: Visual cues locate objects in a scene within the retinal image, unlike audition where the activation point on the cochlea doesn't directly pinpoint location.
Binaural Cues: Sound localisation relies on comparison of signals from both ears.
- Interaural Time Differences (ITDs): The time difference between when a sound reaches each ear. This is crucial for determining azimuth (left-right). If a sound source is directly ahead, there's no ITD. If it's to one side, the nearer ear receives the sound first. ITDs are most useful for low frequencies or abrupt-onset sounds and the range varies depending on the speed of sound (typically 330 m/s), and the distance between ears. The maximum ITD in humans is typically around 600µs (0.6ms).
- Interaural Level Differences (ILDs): The difference in sound pressure level between the two ears. High-frequency sounds are significantly affected by the head's acoustic shadow, resulting in a decrease in level at the far ear. This effect is minimal for low-frequency sounds.
Monaural Cues:
- Elevation: The pinna (outer ear) filters frequencies differently depending on sound source elevation. The relative intensity of different frequencies changes with the sound's source elevation.
- Distance: Sound intensity diminishes with distance. Reverberation (echoes and reflections) also provide cues about distance, by combining multiple reflections.

Interaural Time Differences (ITDs)

The relative time a sound arrives at each ear relates to its location in azimuth (left-right).

Interaural Level Differences (ILDs)

Differences in sound pressure between ears depend on the sound source's location in azimuth. This relies on the acoustic shadow of the head for high-frequency sounds.

Physiology of Binaural Processing

Processing of ITDs and ILDs begins in the brainstem's superior olivary complex.
- Lateral Superior Olive (LSO): Sensitive to ILDs.
- Medial Superior Olive (MSO): Sensitive to ITDs.

Strengths and Weaknesses of Binaural Cues

Complementary information for azimuth, well-suited for low-frequency sounds but not elevation or distance.
Cone of Confusion: A set of possible positions in azimuth that yield identical ITDs and ILDs.

Auditory Scene Analysis Strategies

Spectral Grouping: Grouping sounds based on similar frequencies perceived as likely originating from the same source. Harmonicity plays a role, as does the common frequency changes perceived within a sound source.
Sequential Grouping: Grouping sounds based on common characteristics over time, like timbre and constant or smoothly changing sounds perceived as continuous even when interrupted.
Temporal Proximity: Sounds that occur in rapid succession tend to be grouped together.

Summary

Binaural Cues (ITDs/ILDs): Crucial for azimuth localization, yet they do not provide information about elevation or distance.
Monaural Cues: Used for elevation (pinna filtering) and distance (intensity/reverberation).
Auditory Scene Analysis: Processes the mixture of sounds in a scene, segregating sounds that originate from different sources and grouping those from the same source.

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Description

Test your knowledge on auditory scene analysis and sound localisation. This quiz covers the principles of how we perceive sound sources in our environment, including binaural cues and interaural time differences. Explore the differences between visual and auditory localisation skills.