Chapter 10b: Auditory Event Perception

Question 1

Auditory Scene Analysis
:

Perceptual Segregation

Answer 1

In complex auditory environments, humans are able to focus their attention on one source while ignoring sounds on other sources.

Perceptual segregation is often based on physical properties of a sound, but it is also facilitated by tracking the meaningful aspects of speech sounds.

Question 2

Auditory Grouping Principles

Answer 2

1. Good continuation
2. Similarity of pitch
3. Temporal proximity
4. Similarity of timbre
5. Location

Question 3

Good Continuation

Answer 3

When gaps in a pure tone are coincident with a noise mask, the auditory system “fills in” the gaps so that a continuous tone is perceived.

Question 4

Grouping by pitch Example

Answer 4

African xylophone music 1

The composite piece has two parts, one at a high frequency and one at a low frequency.
Each player plays some notes from each part at an isochronous rhythm (i.e., every note is equally spaced in time).
When the two players combine, however, the high and low parts are perceptually segregated and the perceived rhythm is irregular.

Question 5

Grouping by timbre Example

Answer 5

African xylophone music 2

If the notes of one of the players are muffled so that the two xylophones have different timbres, then the high and low streaming does not occur.
The perception is of two isochronous rhythms.

Question 6

Grouping by Temporal Proximity

Answer 6

beep boop beep boop
….. slow

vs.

beepbeepbeep
boopboopboop
…….faster repitation separates the sounds

Question 7

Grouping by location

Answer 7

When the high and low notes are generated from the same location in space a galloping rhythm is perceived. As the notes become separated in space, however, the left and right streams become perceptually segregated. This demonstration should be listened to in stereo.

the gallops
The same location streaming effect with African xylophone music. This demonstration should be listened to in stereo.

Question 8

Sound recognition

Answer 8

Humans and other animals are able to identify a wide variety of sounds, presumably based on their timbres and rhythms.

Question 9

Shepard Tone:

Answer 9

“Sonic Barber’s Pole” illusion.

The tone sounds as if it is continually ascends (or descends)

Consists of a superposition of sine waves separated by octaves.

Batpod™ sound effect in The Dark Knight