Hearing Science Final

Sound

Fluctuations in air pressure across time

Hearing

Process that transforms sound waves into neural signals that can be interpreted by our brain

Hearing Science

The relationship between the physical properties of sound and the sensations they produce

Sound Waveform

Sound is a longitudinal compression wave

Peak: pressure condensations

Zero: Resting pressure

Troughs: Pressure rarefactions

Sinusoid

Frequency, Amplitude, and Phase

EX: sine waves, complex tones

Spectrum

Frequency and amplitude

EX: white noise

Steven’s Power Law

sensation is compressive

Physical properties of sound that affect loudness

Intensity, frequency, and duration

Outer Hair cells

Amplifiers (top-down)

Take signals from the brain

Efferent

Inner Hair Cells

True receptors (bottom up)

Signals to the brain

Afferent

Tonotopically organized

High frequencies at the base, lower frequencies at the apex

Fletcher’s critical-band experiment

Measure bandwidth of auditory filters

IV: masking noise bandwidth

DV: signal amp @ threshold

control: signal frequency noise amplitude @ threshold

Critical bandwidth of an auditory filter

Measure shape of auditory filter across frequencies

Low masks high

Most affective masking to least affective

Forward Fringe, Backward Fringe, Forward Masking, Backwards Masking

Central Masking

Occurs during dichotic listening conditions due to a central mechanism

What frequency range can the temporal theory explain pire-tone pitch perception

Low frequency under 1000 Hz

Uses phase locking

What frequency range can the place theory explain pure-tone pitch perception?

Best for high frequencies above 2000 Hz

works for low and high

Three main aspects of spatial perception

Azimuth angle, elevation angle, distance

What aspect of spatial perception are humans most sensitive to?

Azimuth angle

Duplex Theory

ILD’s are best for high frequencies, ITD’s are best for low frequencies

Main attributes for English consonant classification

place, manner, and voicing

Primary determinant of a speaker’s pitch

Acoustic source

Major acoustic properties for determining English vowels

Formant frequencies (mostly F1 and F2)

Main signal processing strategy used in modern hearing aids

Compression

Linear vs Non-Linear

Linear - constant gain

Non-Linear - gain changes with input level

How do cochlear implants work?

They bypass damaged hair cells and directly stimulate the cochlea

What is one aspect of cochlear implants that are significant to them

Vocoding

Main difference in candidacy between hearing aids and cochlear implants

Degree of hearing loss