Sound Localization and Identification

Azimuth

The location of a sound source in the horizontal plane (left or right).

Elevation

The angle of a sound source above or below the horizontal plane.

Distance

How far a sound source is from the center of the head in any direction.

Minimum Audible Angle

The smallest angular separation between two sound sources that allows 75% correct identification.

Acoustic Shadow

The head blocks sound waves, reducing intensity at the far ear.

Interaural Level Difference (ILD)

The difference in sound intensity between the two ears.

Interaural Time Difference (ITD)

The difference in arrival time of a sound at each ear.

Cone of Confusion

A region in space where sound sources produce identical ILD and ITD, making localization ambiguous.

Spectral Shape Cue

Changes in a sound's frequency spectrum caused by the pinna, helping determine elevation.

Doppler Effect

A moving sound source has a higher frequency in front and lower behind; frequency drops as it passes the listener.

Echolocation

Using emitted sounds and their echoes to determine the location and nature of objects.

Auditory Scene

All sounds entering the ears at a given moment.

Auditory Scene Analysis

The process of separating and identifying different sound sources from a mixture of frequencies.

Auditory Stream

A sequence of frequencies perceived as coming from the same source.

Auditory Stream Regulation

Organizing sound input into distinct perceptual streams.

Simultaneous Grouping

Grouping sounds that share harmonic relationships or start/stop together.

Sequential Grouping

Grouping sounds that are close in frequency or time, perceived as coming from the same source.

Frequency Theory

Suggests the entire basilar membrane vibrates in sync with the sound frequency; limited by neuron firing rate (~1000 Hz).

Békésy's Place Theory

Different parts of the basilar membrane respond to different frequencies; high frequencies near the base, low near the apex.

Decibel (dB)

A unit measuring sound intensity; higher dB = louder sound.

Prolonged Exposure

Exposure to sounds above 85 dB can damage hair cells (cilia) in the cochlea, leading to hearing loss.

Absolute Threshold of Hearing

The quietest sound detectable by the average human ear; typically 0 dB.

Presbycusis

Age-related hearing loss, especially affecting high-frequency sounds due to damage near the base of the basilar membrane.

Hertz (Hz)

the unit of measurement for frequency, which refers to how many times something occurs per second.

Inverse Square Law

Sound intensity decreases proportionally to the square of the distance from the source (Intensity ∝ 1/distance²).

Fundamental Frequency

The lowest frequency of a sound; determines perceived pitch.

Fourier Analysis

A mathematical method (performed by the cochlea) that breaks complex sounds into individual sine wave components for analysis.