Sound source segregation

Development of the ability to separate concurrent sounds into

auditory objects

The problem…

TIME

FR

EQ

UE

NC

Y

Wow! Psychophysics is interesting!

Cues that adults use to segregate components into sources

Spectral separation Spectral profile Harmonicity Spatial separation Temporal separation Temporal onsets and offsets Temporal modulations

Measuring sound source segregation Auditory streaming “Thresholds” of sounds, segregated and not

segregated Informational masking (indirect evidence)

Auditory streaming

A single sound source is perceived

Two sound sources are perceived

Auditory streaming in infants

How many streams

that time?

Auditory streaming in infants

Auditory streaming in infants

Configuration 3/1 Configuration 2/2

Electrophysiological measures of streaming in newborns

Auditory streaming in children

Auditory streaming in children

Another way to look at auditory streaming in children

Electrophysiological measures of streaming in children

Electrophysiological measures of streaming in children

ConclusionInfants and children form “auditory

streams.”

Thresholds of sound, segregated and not segregated Spatial cues Synchronized visual information

Masking level difference

The MLD is the improvement in audibility that results from dichotic listening

N= noise, S = signal

Monotic = one ear (m)

Diotic = 2 ears, same sound in both (0)

Dichotic = 2 ears, different sound in each (π)

Modified from Gelfand (1998)

MLD in infants

MLD in children

Spatial unmasking

Baseball

(noise)

(noise)

Spatial unmasking in preschool children

Spatial unmasking in school-age children

Preferential looking procedure

baseball, baseball, baseball

(“Twenty subjects were tested…”)

baseball, baseball, baseballpopcorn, popcorn, popcorn

Speech in speech recognition in infants

Visual information improves speech in speech recognition in infants

Testing whether children can segregate speech from speech

Ready Baron go to Blue 3 nowReady Ringo go to Red 5 now

Visual information doesn’t improve speech in speech recognition in children

Conclusions Infants and children are more sensitive to sounds

that can be segregated from competing sounds, although infants show less benefit of segregation cues.

Under simple conditions, even 3-year-olds can use segregation cues as well as adults.

Under complex conditions, even 10-year-olds do not use segregation cues as well as adults.

Informational masking Interval 1 Interval 2

Leve

l

Frequency

Trial

1

2

3

Informational masking in children

Informational masking in infants

Information masking in infants

Fixed, remote frequency masking in children

Informational masking?Interval 2

Leve

l

Frequency

Trial

1

2

3

Interval 1

Using temporal cues to reduce informational masking

Summary and conclusions Infants and children can segregate sound

sources, using the same acoustic cues that adults use.

In simple situations, children, but not infants, can segregate sound sources as well as adults.

In complex situations, sound source segregation may not be mature until well into the school years.