Audition Final

What do we search for in psychoacoustics?

We search for behaviour as a function of stimuli

What are the sound properties of psychoacoustics?

- Intensity

- Frequency contents

- Temporal pattern

What are the behaviour properties for psychoacoustics?

- Loudness

- Pitch

- Temporal pattern

- Timbre

What are the 4 functional relationships between behaviour and stimuli?

- Detection (quietest sound that can be heard)

- Discrimination (the smallest difference in stimuli that can be detected)

- Identification (identifying target among several sounds)

- Judging (how loud sound A is compared to sound B)

What is an analytical study?

A comparative study designed to reach causal inferences about hypothesized relationships between risk factors and outcome

- these studies investigate the roles of individual acoustic parameters (intensity, frequency, temporal patterns)

- bottom up processing

What is an integrated study?

An integrated study investigates an aspect of perception that requires an integration of multiple sound properties

- top down processing

What are some examples of integration in psychacoustics?

- Timbre

- Sound localization

- Auditory perception

What is an example of analytical studies in pyschoacoustics?

how any acoustic parameters are detected, discriminated, identified

What is integration?

The process of neurons across different auditory channels (different location in one nuclei) (integration of information from multiple different neurons)

What type of processing do hearing studies test?

Top down processing

What is another word for limen?

threshold

What are the 3 dimensions of auditory ability?

absolute limen

terminal limen

difference limen

What is the absolute limen?

- the lower boundary of detection

- aka the minimum threshold to detect sound

What is the terminal limen?

- the upper boundary of detection

- aka the maximum threshold we can hear before sound perception stops increasing and pain occurs

What is the difference limen?

the smallest change in some aspect of the stimulus which can be detected

What are the two ways a senstivity curve can be tested?

- In an open field through a speaker

- In a closed field through earphones

What are minimum audibility curves?

sensitivity across frequency range (also called audiogram)

What is the frequency range of hearing?

20-20,000 Hz

According to the minimum audibility curve, sensitivity is best at what frequency range?

~ 2000-3000 Hz

Terminal threshold is ____________, while audibility curve is ___________. (shape)

Terminal threshold is fairly flat, audibility curve is curved

What are the two categories of terminal threshold? And which one is most likely to be used clinically?

- Threshold of discomfort (most likely to be used)

- Threshold of pain

What is dynamic range of hearing?

The difference between the absolute and terminal limen, ie. the range of hearing

- range between softer sound you can hear and loudest sound you can tolerate

What does dynamic range vary with?

frequency --> largest at middle frequency

How is the threshold statistically determined?

- tested in multiple trials at each level to calculate % correct

- threshold is obtained based upon a criterion of correct responses selected

- corresponding sound level is determined as threshold

What is the principle of the threshold determination technique?

The average of results must be well above the percentage of chance (ie. outcome of guessing) (above 50%)

What is the average threshold variability?

Thresholds can vary by 20 dB across individuals with normal hearing (-10 dB to 10 dB)

What is the average threshold reliability for one individual? (test-retest)

10-15 dB

What does test-retest reliability show?

- If the test is reliable or not

- If the subject has hearing loss

The range when obtaining a hearing test depends on:

accuracy of method and skill level of performer

Random air particle movement will produce sound pressure only ___________ dB below our minimum audibility curve around _______________ Hz.

Random air particle movement will produce sound pressure only 10-15 dB below our minimum audibility curve around 1000-6000 Hz.

What kind of graph is the general absolute threshold?

open V shape

What contributes to the formation of the audibility curve?

External, middle ear, cochlea frequencies

How can we test if the cochlea is contributing to the audibility curve?

Through bone conduction test

- we do not get a flat frequency response from bone conduction which proves cochlea

What is Minimum Audible Field?

Seat the subject in a sound field and test his thresholds for sounds presented through a loudspeaker, then sound is measure when subject is absent

- binaural

What is Minimum Audible Pressure?

Testing a subject's thresholds through earphones, then monitoring the sound pressures in the ear canal

- monaural and measured with a coupler

Which has a lower minimum threshold? Minimum Audible Pressure or Minimum Audible Field?

MAF has about 6dB lower than MAP

What were the three potential reasons proposed for the 6 dB difference?

- MAP eliminates external ear resonance, resulting in amplification loss

- Binaural summation in MAF

- Physiological noises heard in MAP

What is the current view on MAP vs. MAF?

- Missing 6 dB problem does not exist

- If calibration is done, there is no difference

What is the Reference Equivalent Threshold SPL?

- It is a way to calibrate audiometric equipment at 0 dB threshold for different frequencies.

- It is the allowance of background noise during testing

- Our guideline for how much ambient noise is allowed

- Gives us a standard

What is a coupler?

- a tool to measure sound pressure

- man made cube meant to mimic the human ear

What is masking?

when one sound interferes with the sensation of another sound

True/False. Masked threshold is usually higher than the threshold in quiet

True

If a masker has a higher frequency than the tone, there will be a __________ masked threshold.

Lower

aka weaker masking effect

What is SPL?

- reference of physical sound pressure (if a sound is played at a certain level, its played at an objective level, the level that we hear it at is subjective, what changes it is our perception of how loud it is)

- 20 dB SPL is a level of intensity

What is HL?

reference of hearing thresholds of normal subjects using RETSPL

What is SL?

- reference of hearing thresholds of normal subjects using RETSPL

- sensation level is your own audibility threshold

When is there more allowance of noise with RETSPL? WHY?

when using earphone, the attenuation level by earphone is added so more noise is allowed

What is the way to say the difference threshold as it relates to intensity?

Defined as the minimal intensity difference that can be detected (also called JDD --> just detectable difference)

What is Weber's law?

the smallest intensity difference that can be detected is a function of the amount of intensity

What is Weber's law as it relates to intensity?

Predicts the relationship between delta I and I: delta I is proportional to I. Therefore, it is expressed as: delta I/I = constant

Smaller delta I means:

less of a difference is needed for detection

Based on Weber's law, what was the graphical expectation?

If Weber's law was 100% correct, delta I/I would be plotted against I as a horizontal line

What is the intensity discrimination for pure tones?

~1 dB (or ~0.3 in delta I/I)

Based on the results, what is Weber's law described as?

Near missing

What do the results of Weber's law show?

for pure tones, the intensity discrimination at a higher level is better than expected (Weber's fraction is smaller than expected)

What type of sound follows Weber's law better?

white noise

How does the intensity discrimination threshold for white noise compare to pure tone?

More accurate for broad band signal (white noise)

What are 3 methods to play the sound for the intensity discrimination task?

- gated pulse tone

- continuous tone pulse increment

- modulation tone

What is gated pulse tone?

- Can present sound in time sequence (present 1 sound, then another impulse several seconds later)

- we call this gated pulse tones (tone bursts presented in short periods of time) and ask subject to tell you which one is louder

--> This test relies on short term memory, need to remember the loudness of first sound

--> Interval between two signals will change outcome (longer interval = poorer performance)

What is continuous tone plus increment?

- increase level for short period of time and ask whether they heard a continuous tone or heard the increase

--> This method diminishes the impact of short term memory, but creates a new issue of adaptation (sensation decline against long lasting signal)

What is modulation tone?

- tries to reduce the impact of short term memory and adaptation

--> The sine wave with no modulation amplitude should be the same, but we modulate it so the level of sound goes up and down (we can adjust size of modulation)

What are possible confounds for two of the tones? Which is recommended?

gated pulse tone --> relies on short term memory

continuous tone pulse increment --> issue of adaptation (sensation decline along long lasting signal)

modulation tone is recommended

Which method has a lower threshold between the continuous pedestal compared to the gated method?

Continuous

What is loudness?

- loudness is the perception of sound strength, mainly related to sound level

- loudness is a subjective concept and can only be tested behaviourally

What other factors affect loudness?

Frequency, duration, existence of other signals

Based on the arbitrary scale, what was the general criteria for loudness in terms of how many dB results in what multiplied change in loudness?

10 dB level change results in 2x change in loudness

In the SL measurement, what does that SL stand for? What is is the 0dB in this case?

SL refers to sensation level, which is established using individual threshold as reference (0 dB)

For the original loudness scale, what was the frequency used and at what intensity to get the arbitrary units?

800 Hz tone at 100 dB SL

What was used in the frequency and intensity used in the sone scale to define the arbitrary one sone?

1000 Hz at 40 dB tone

As per the sone scale, what is the doubling or halving?

Doubling or halving: 2 or 0.5 sones

When there is a 10dB change in the intensity, how many times does the Sone change by?

2

At which level does the general idea that a 10dB change in intensity results in a 2 time change in loudness not apply?

at low SPL close to threshold

For the equal loudness contour, what scale is used? What does the phon scale use as its reference?

Phon scale

Uses 1000 Hz

How are the other phons obtained?

at other frequency, SPL is determined by equal loudness using 1k references at each phon

Overall, what is the difference in the continuous shape for the low SPL and the high SPL?

- Ceiling is flat

- Lower boundary is curved

What does the dynamic range measure?

the SPL difference between the floor and ceiling

What is changed and what remains the same in dynamic range?

Ceiling is NOT changed while floor varies

What is the most sensitive region? What does the dynamic range look like in this sensitive region (small or large)?

- 1000-4000 Hz is the most sensitive region (lowest threshold)

- Largest dynamic range

What is a characteristic of the low frequency on the dynamic range curves?

Smaller dynamic range and faster loudness growth at low frequency

What are the two characteristics that the loudness contour shows the impact of the sense of sound?

Boomy

Tinny

What is Boomy?

too much low pitch when the signal is played back at a higher level than recorded

What is Tinny?

Tinny - hear more high frequency when played back at a lower level than recorded

What is a sound level meter?

measuring device for environmental noise

Which filter network is used for quiet environment? Where is there more weighting for this?

Which for high level of noise?

dB A, high pass filter (Remember, these are the filters used in a sound level meter to make the instrument more nearly approximate the normal human ear. The different contours were intended to match the ear at different sound intensities so they are relative sound pressure levels. In quiet, it is like the 40 phon curve (page 208 textbook) where the low frequencies are de-emphazied and the high frequencies are passed efficiently)

dB C

What are filters?

- used for sound level meter

- makes a sound level meter more approximate for human ear

- Filters are used to better quantify the sound to make it more suitable for the sensation that humans hear

If a masker had a lower frequency than the tone, there will be a ___________ masked threshold.

Higher

aka stronger masking effect

What happens to the acoustic parameter above when increasing the bandwidth of the signal to beyond that critical band? Why?

the loudness will increase because it is above threshold, so will excited other auditory channels

What happens to loudness when increasing within the critical band?

Loudness will not change

How can loudness be maintained as the bandwidth changes?

Think of it as a trade off

If bandwidth increases, decrease intensity so loudness can be maintained

What is adaptation? When is sensitivity back?

- Decrease of sensitivity during signal presentation - reduced response to non-novel signal

- if a new signal comes up

How is fatigue different than adaptation?

decreased sensation AFTER signal presentation and reduced sensitivity to all stimuli

How is adaptation measured?

By loudness matching where one ear hears a continuous sound and other ear receives a pulse signal, see the change over time

What kind of signal is not adapted?

Pulsed signal

What were the three main results from the loudness matching experiment?

*Specific to binaural presentation

1) large variation across individuals

2) more significant matching at low sound level

3) more matching at high frequency

What is the take-home message of adaptation?

Adaptation is level dependent, larger adaptation at lower sound levels and large variation across individuals

What is masking?

when one sound interferes with the sensation of another

How does masking impact the loudness growth curve?

- When there is making, threshold (floor) is elevated and the ceiling doesn't change

- dynamic range is narrower

- result is a flat growth

What kind of noise can be a masker?

- Broadband (best)

- Narrow band

- Tone

What does partial masking do?

Partial masking reduces loudness sensation of test signal

Which is a better masker; pure tone or noise?

Noise