Hearing Science Final Exam

The bigger the initial stimulus

the bigger change needed to notice a difference

It is harder to notice a difference when

the initial amount is already large

The concept of greater sound needing greater difference to hear is called

just noticeable difference

What does absolute difference mean?

Specify the actual physical difference needed to tell 2 sounds apart

What does sensation level mean? How do you calculate it?

The number of decibels above a threshold

How do you calculate sensation level?

Subtract the difference between the presented tone’s dB and the patient’s threshold

Gap detection threshold

Shortest discernible gap

To determine the perceived order of sounds an interval of

20 milliseconds is needed

Fletcher Munson Curve

Graph that shows equally loud dB SPLs across different frequencies, so they can all be perceived at the same level

Will tones on the Fletcher Munson Curve sound equally as loud even though their dB SPLs are different?

Yes

Do lower or higher frequencies need a greater intensity to be heard at the same level as their counterparts?

Lower intensity

When any point on the line of a Fletcher Munson is equally loud, this is referred to as

equal loudness contour

__ is a physical measure, __ are a perceived measure

intensity, phons

__ is a unit of perceived loudness level

phons

Why are the phons only at 1000Hz on the Fletcher Munson Curve?

It is the reference point for other frequencies on the equal loudness contour

Phons are directly linked to the decibel level of

1000 Hz tone

What is dB SPL?

The amount of pressure a sound exerts

Is dB SPL a physical measurement?

Yes

Does dB SPL measure sound intensity

Yes

Is there a JND for points on the same line of the Fletcher Munson Curve

No, they are all perceived to be the same loudness

Sones show

loudness intensity relationship based on methods

Sones are

a unit of loudness

What is the reference intensity for the sones scale?

40 dB at 1000Hz Tone= 1 sone

Why use sones?

Decibels are not easy to perceptually interpret

Sones are a

linear scale

What does linear mean?

Doubling the sone value results in a sound that sounds twice as loud

Doubling or halving the loudness in sones corresponds to

10 dB increase or decrease

Phons ___, while sons __

are tied to frequency, measure how much louder one sound is compared to another

When phons increase by __, sons __

10, double

Critical band

A small range of frequencies that are grouped together

When sounds are further apart in different areas

they are easier to tell apart and are therefore in different critical bands

What is bandwidth of sound?

The range of frequencies a sound is referring to

Auditory system perceives frequencies in the same critical band

as a single unit

Critical bandwidth becomes __ as the center frequency gets higher above 1000Hz

broader

As the frequency increases, the critical band includes __ frequencies

more

__ precise hearing at low frequencies, __ precise hearing at high frequencies

More, less

Pitch is the physical correlate of

frequency

Frequency is __ per __

cycles, second

The lowest frequency that is associated with “tonality” or perceptible
pitch =

20 Hz

Frequencies above 1000 Hz need to be

at least 10 milliseconds

Frequencies below 1000 Hz need to be

longer than 10 milliseconds

Why do we have a mel scale?

It is a way to measure frequency in a way that makes sense to us and how we actually perceive the sound

Do we hear pitch in a linear way

No

Unit of pitch

Mel

Sone scale relates

intensity and loudness

Mel scale relates

pitch and frequency

Reference point for mel scale

1000 Hz tone at 40 phons

Reference point for mel scale

Has a pitch of 1000 mels

We are more __ to changes at lower frequencies

Sensitive

__ are the building blocks of complex waves

Sine waves

Parameters for sine waves

frequencies, amplitudes, phases

Lowest frequency component of a complex wave

fundamental frequency

Harmonics

Integral multiple of the fundamental frequency

The first harmonic is always

the fundamental frequency

Pitch you perceive but don’t hear is called

Residue pitch

__ is important for encoding frequency in our CANS

Temporal factors (timing)

Distortion products

Any signal that is present in the output of a system that was not present in the input of a system

Input

Sound from environment entering your ear

Output

Sound you hear

How are distortion products produced?

Nonlinear distortions in the cochlea produce sounds that are not part of the input

Masking

When the presence of one sound makes it hard to hear another

Main concern of masking

The interaction of sounds

Central masking

Sound in one ear, masking in the other ear

Temporal masking

Signal and masker are not presented at the same time

Forward masking

Masking comes before the signal

Backward masking

Signal comes before the masker

Components of a masker

Frequency and intensity

What makes a masker effective at masking out the presentation tone

Masker with frequencies similar to the signal’s frequency

What does psychoacoustic tuning curve show?

The masker levels at each frequency needed to mask the test tone

Upward spread of masking

Masking extends to frequencies that are higher than the masker but not below it

Why do low frequency sounds more effectively mask high frequency sounds?

The cochlea is tonotopically organized, so the lower frequency sounds pass the areas of the cochlea responsible for processing higher frequencies, masking them.

Threshold of hearing is 3dB lower

when listening with 2 ears compared to one

Advantage of using both ears

Binaural summation

Azimuth estimation

Horizontal plane, front, right back

Elevation estimation

Vertical plane, above and below your head

Distance estimation

Is the sound far away or close by?

Monaural is important for

vertical and elevation estimation, not as important for azimuth estimation

Binaural is helpful for

Determining which ear sound is being presented

What helps determine the vertical plane?

Sound waves being reflected off the pinna

Monaural localization cue

Pinna sound waves being reflected

Binaural localization cue

Horizontal plane, interaural

Interaural

Difference between left and right ear

Interaural intensity difference

Difference between intensity of left and right ear

IID for High frequencies

Higher frequencies have shorter wavelengths, more easily blocked by the head as they pass from one side to the other, therefore more easy to tell which side it is coming from

Interaural Time Difference

AKA Interaural phase difference, sound will take longer to arrive at opposite side, this tells which side the sound is coming from

Head related transfer function

Describes how sound interacts with a listener’s heads, ears, and torso, affecting how the sound reaches the eardrum

Binaural hearing

Term used to describe the nature and effect of listening with 2 ears instead of 1 ear

Benefits of binaural hearing

Localizing sound sources, better speech understanding in noise, increased loudness

Binaural fusion

Separate signals received by the two ears are perceived as a single, fused auditory image

Binaural fusion occurs as long as

there is similarity between 2 signals, esp. true for frequencies less than 1500 Hz

Extracranially

Sound coming from outside your head

Intracranially

Signal heard “inside” the head, ie when wearing headphones

Why is HRTF not preserved when wearing headphones

Because sound is not traveling over the head, torso, and pinna like sound in the environment does

Are there interaural differences if the sound source is directly in front or behind the listener?

No, because these locations are equally distant from the ears

Minimum audible angle

Smallest perceptible separation between 2 sound sources, difference limen for localization

When a sound is in front of a listener, the change can be __ detected than when the sound is to the side

better

Cone of confusion

On each side of the head, there is the same interaural differences present, thus making it hard to pinpoint sound location

MAA is __ in front of the head

acute

Precedence effect

Sounds are reflected back when they hit a surface

Reverberation

When sounds linger after the original sound is presented