CHAPTER 12

Sound Localization and

Binaural Hearing

Binaural Hearing: Some Terms

• AZIMUTH-angle from straight ahead in horizontal plane.

• Minimum Audible Amgle- jnd for azimuth.(smallest at 0 degrees, largest near 90 and 270 deg.)

Binaural

LOCALIZATION & LATERALIZATION

LOCALIZATION:

• ability to determine location of a sound source in the sound field.

LATERALIZATION:

• perceived position of sound within your head for stimulation under headphones.

Binaural

Sound Localization

Bin

aura

l

LOCALIZATION CUES:

• INTERAURAL TIME DIFFERENCE works best at low freqs: up to 0.65 ms at 90 deg.

• INTERAURAL INTENSITY DIFFERENCE works best at high freqs: where head shadow exists.

• PRECEDENCE EFFECT people can tell which ear was stimulated first.

Binaural

Masking Level Difference (MLD)

Masker and Signal in Each Ear

Test Threshold twice:

> once with identical signals in each ear

> once with 180 degrees out of phase R to L

Binaural

Masking Level Difference (MLD) (cont’d)

• Signal is easier to detect with the interaural phase difference

• Shift in threshold is about 12 to 15 dB at low frequencies.

• Reflects processing in the auditory brainstem)

Binaural