Intro Audiology Module 4

psychoacoustics

The study of the relationship between physical sound stimuli and our psychological responses to those sounds

Physical properties of sound, such as frequency and sound pressure level (SPL).

What is physical acoustics concerned with?

pitch

The subjective experience of frequency — how high or low a sound seems.

Frequency (Hz).

What is the physical correlate of pitch?

Pitch increases (the sound seems higher).

What happens to pitch when frequency increases?

The sound goes up one octave

What happens when frequency is doubled?

1,000 Hz and 2,000 Hz are one octave apart.
2,000 Hz and 4,000 Hz are also one octave apart.

Give an example of frequencies that are one octave apart.

No. Doubling frequency raises pitch by one octave, but pitch itself does not simply double.

Does doubling frequency double pitch?

Mel

What is the unit used to measure pitch?

A tone is presented, and the listener adjusts a comparison tone until both tones sound like the same pitch. The comparison frequency is then reported.

How is pitch measured in mels?

No. The numbers on the mel scale do not correspond directly to frequency in Hz.

Are mels and Hz directly equivalent?

No. Mels are roughly proportional to Hz up to about 500 Hz, then the curve begins to flatten.

Is the relationship between Hz and mels linear?

Equal changes in frequency (Hz) do not create equal changes in perceived pitch.

What does it mean that the mel curve "flattens"?

loudness

The subjective experience of intensity — how loud or soft a sound seems.

intensity

What is the physical correlate of loudness?

Yes. Our perception of loudness changes at different frequencies.

Does the perceived loudness of a sound depend on frequency?

Phon

What is the unit of loudness level?

A 1,000 Hz tone is set at a specific level, and listeners adjust other frequencies until they sound equally loud.

How is loudness level measured using phons?

It is used as the reference tone to compare the perceived loudness of other frequencies.

Why is a 1,000 Hz tone used when measuring loudness?

Loudness grows faster for low-frequency tones than for mid-frequency tones.

What happens to loudness growth for low-frequency sounds?

sone

A unit that describes perceived loudness proportionally.

The loudness of a 1 kHz tone at 40 dB SPL.

What is 1 sone equal to?

• dB = what the sound/air is doing

• Phons = what the listener judges as equally loud

• Sones = how loud the listener judges something proportionally

What is the difference between dB, phons, and sones?

sound localization

Determining the direction a sound is coming from without directly seeing the source.

Differences in intensity and time of arrival between the two ears.

What two main cues help us localize sound?

Interaural time differences (ITDs).

What cue is mainly used for low frequencies?

Frequencies below 1,500 Hz.

What frequency range mainly uses interaural time differences?

Because low-frequency sounds bend around the head, so both ears receive nearly the same level, making time differences more useful.

Why are ITDs useful for low-frequency sounds?

Intensity differences between the two ears.

What cue is mainly used for high frequencies?

Frequencies above 1,500 Hz.

What frequency range mainly uses intensity cues?

Their wavelength is smaller than the head, so the head creates a larger difference in sound level between the two ears.

Why are intensity differences useful for high-frequency sounds?

masking

When one sound is loud enough to make another sound difficult or impossible to hear.

Background noise in a restaurant can interfere with speech recognition and make it harder to understand someone talking.

Give an example of masking.

One sound may be intense enough to cause the other sound to become inaudible.

What happens when two sounds are heard at the same time?