Audition Final Test

What is psychoacoustics and the main goal of this science?

The psychology in hearing science. The goal is to investigate how the behavior are resulted from the stimuli.

What is the difference between "psychoacoustics" and "Psychophysics"?

Psychoacoustics refers to the behavioral consequences of acoustic stimuli, but psychophysics refers to the sound properties and behaviors.

What are the three properties of sound?

Intensity, frequency contents, temporal pattern

What are the four functional relationships?

Detection, discrimination, identification, judging (scaling)

Describe Detection

It refers to determining whether the signal is there or not

Describe Discrimination

It is judging a difference when two signals are presented

Describe Identification

It is the ability to point out which one is the target signal amidst other sources

Describe Judging

It is thought of as 'scaling' in which the response is quantified

What are the corresponding behaviors to the sound properties?

Intensity- loudness/ frequency- pitch/temporal pattern (timing)

What are the two big categories for these psychoacoustic studies?

Analytic and integrative

What is the difference between analytic and integrative (psychoacoustic studies)?

Analytic refers to the roles of the individual acoustic parameters (intensity, frequency and temporal patterns), but integrative studies look at how the integration of the individual parameters relates to our perception. Overall, analytic is more related to the detail and integrative is like the big picture studies (the overall meaning)

What are examples of an analytic psychoacoustic study?

How the acoustic parameter (intensity, frequency and temporal pattern) are discriminated, identified and scaled.

What are examples of an integrative psychoacoustic study?

Sound localization tasks when using different cues in time and spectrum OR the notion of 'timbre' which relates to quality of a complex sound, integration of frequency components, intensity and temporal patterns (not a study) OR auditory perception tasks since it is the acoustic image in a complex sound field.

Define integration?

It is the process of neurons across different auditory channels (different location in one nuclei), different types of neurons, and different nuclei, excitation versus inhibition, afferent versus efferent.

What is the difference between a 'top down' and bottom up' process as it relates to the auditory system?

Top down means how experience and knowledge affect what we hear and bottom up is how what are hearing and picking up (the physical feature of sound) is affecting the perception. The meaning versus the language itself

What is another word for 'limen'?

Threshold

What are the three dimensions of auditory ability?

Absolute limen, terminal limen, difference limen. The lower boundary, upper boundary and smallest change in some aspect of the stimulus which can be detected, respectively.

What is sensitivity as it relates to hearing thresholds?

The absolute threshold sound intensity and pressure (what we do in audiology audiogram)

What are minimum audibility curves?

The sensitivity across frequency range.

What is the frequency range of hearing?

It is the limits at the two ends, 20 to 20000Hz

What is the terminal threshold?

The upper limit also known as the threshold of discomfort and threshold of pain

What is the dynamic range of hearing?

The range between the terminal and minimum audibility curve.

Why is it the dynamic range of hearing called that?

It is "dynamic" considering the loudness changes as a result of sound level changes

What does dynamic range vary with?

Frequency and the largest at the middle frequency (so greater distance between the minimal threshold and the terminal threshold, i.e., where it becomes too loud and uncomfortable)

Briefly, how is the threshold statistically determined?

Not only by guessing but there are multiple trials and the percentage that is correct

What is the variability that can be seen when measuring the hearing thresholds?

It is the individual variation and can be as much as 20 dB for those with normal hearing across individuals so even a person with -10 or a person with 10db, it's a 20dB difference, yet both would be considered normal hearing

What is one way to try and help combat the variability seen when measuring the hearing thresholds?

Test-retest reliability.

What is common for a test re-test reliability?

10 to 15dB.

What does the range depend on for what is obtained when testing hearing?

The accuracy is based on the skill level of the performer (clinician or in a lab, the lab researcher, and the method)

What kind of (shape) graph is the general absolute threshold?

An open V shape (i.e., it slopes downward as it approaches the middle frequency (lower threshold) and then goes upward (higher thresholds for the higher frequencies)

What contributes to the shape of the general absolute threshold?

The middle ear resonance, external ear resonance and cochlea (still not exactly sure)

How was the cochlea's contribution tested?

Using bone conduction since that is a way to bypass the external and middle ear. (Note: we hear sounds through the vibration of the skull- bone conduction- in addition to passing through the ears)

What does MAF and MAP stand for?

MAF is the minimum audible field and uses speakers, while MAP is minimum audible pressure and uses earphones.

What is the decibel difference between the MAF and MAP and how is it accounted for?

There is a 6-10dB difference with the MAF having a lower threshold than MAP.

What is the reason for the decibel difference between MAF and MAP?

They originally thought other reasons for this, however realised it was the coupler

What is a coupler?

A 'man made' cube that is meant to mimic the human ear based on impedance characteristics.

Why is RETSPL (Reference Equivalent Threshold Sound Pressure Level) measured?

It is a coupler to measure sound pressure so that it can quantify the sound pressures relationship to voltage and so the reference is equal across different labs.

Which coupler size is used for supra aural earphones and which is for insert earphones?

6cc for supra aural (bigger coupler) and 2cc for insert (smaller coupler); Aside memory aid: Supra aural as in it covers the auricle and insert as in you insert to the ears.

What are the 3 main applications RETSPL (Reference Equivalent Threshold Sound Pressure Level) is used?

(1) Reference for speaker/earphone calibration in clinic, (2) Establishing hearing level using RETSPL zero point- 0 dB HL, (3) allowance of noise in the previous two (just to ensure that the background noise is tolerable and lower than the sound level being targeted)

What is the difference between SPL, HL and SL?

SPL is the reference of the physical sound pressure, HL is the reference of hearing thresholds of normal subjects based on RETSPL (reference equivalent threshold sound pressure level). Sensation level is measured relative to an individual's threshold (i.e., an individual's threshold would be considered 0 dB SL).

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

In the situation when using earphones, they are able to block out more sound (they are in the canals), therefore the background noise is attenuated (lowered/blocked out better) so more noise is allowed. This is also why the ear phones (closed field testing) is better when you are doing a bedside evaluation, that is, an evaluation that is not in the controlled soundproof audio booth but is in a place that has a lot of background noise.

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

The JDD (just detectable difference)

What is Webers law?

A law for sensory discrimination.

What is Weber's law that is related to intensity?

The smallest intensity difference that can be detected as a function of the amount of intensity. The relationship between the just detectable difference (the minimal intensity difference that can be detected) is proportional to the intensity and therefore, it is a constant shown by the ratio between the delta I (JDD) over the I.

What does a smaller delta I mean?

That less of a difference is needed for detection.

What will be the delta I (JDD) if the intensity is 1000, and it is known that I= 10 units and the delta I is 0.5 units?

The answer is 50 units (cross multiple or think ratio, it takes two decimal places from 10 units is 1000 and so moving the delta I also two decimal places from 0.5 is 50 units)

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

Expect a horizontal line.

What is the intensity discrimination for pure tones?

1dB

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

Near missed

What did the results show for Weber's Law?

They showed that at higher sound levels, the threshold is better than what was predicted from Weber's law. Instead of going horizontal, it actually slopes downward as in there is a lower delta I or lower just detectable difference (smallest intensity difference that can be detected). As a reminder, the rough estimation for intensity discrimination is about 1 dB (that is, we are able to generally notice something is louder when it changes by about 1dB)

What type of sound follows Weber's law better?

White noise (as in it shows as a horizontal line/constant for relationship between the intensity difference limen and sound pressure level (dB)

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

It is smaller.

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

Gated pulse tone, continuous tone (and increments also known as the pedestal method/pedestrian detection method) and modulating the tone

What are possible confounds for gated pulse tone and continuous tone? Which is therefore recommended?

For the gated pulse tone, it relies on short memory since you have to remember the first tone; the continuous tone plus increment is influenced by adaptation since you get used to hearing the baseline signal so may not really notice the difference; the modulation tone method is more reliable to overcome the other two.

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

The continuous pedestal method gives a lower threshold.

What is loudness?

The perception of sound strength, and related to sound level. It is subjective and can only be measured behaviorally (ie. The response from the subject)

What other factors affect loudness?

Frequency, duration, other signals presence

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?

A 10db level change results in 2 times of loudness. (That is, if something goes 10dB higher, we would say "that's twice as loud" based on this scale)

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

Sensation level where the individual's threshold is 0dB and the variation from that is for the loudness

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

800 Hz tone at 100dB

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

1000hz with a 40 dB tone.

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

2 or 0.5 sones.

What is the general equation to convert the sone loudness to intensity (where it is a physical unit, not dB)

L=KI to the power of e where L is loudness, K is a constant (not important here), I is intensity and e is exponent

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 the low levels.

For the equal loudness contour, what scale is used?

Phon scale; How we perceive it as loud doesn't depend on the actual SPL.

What does the phon scale use as its reference?

It uses 1000Hz, and at this frequency, the Phon is equal to the SPL.

How are the the other phons obtained?

The SPL s based on the equal loudness of that 1k reference curve. For 200hz, has to be 12 dB before can hear it (find it on the y axis);

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

At the low SPL requiring the same phon is largely varied with frequency. At the high, the variation across frequencies is less.

what does the dynamic range measure?

The SPL difference between the floor and the ceiling.

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

The ceiling is not changed (the upper limit) but the floor varies

What is the most sensitive region (in terms of dynamic range and loudness growth)?

1000 to 4000Hz

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

Large

What is a characteristic of the low frequency on these curves (dynamic range & loudness growth)?

There is a smaller dynamic range and faster loudness growth.

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

The boomy and tinny sounds

Describe the characteristics of boomy and tinny sounds

Boomy refers to that low pitch, resonant sound that is apparent when amplified. Tinny refers to the higher pitch that becomes audible when at a lower level.

What is a sound level meter?

A sound level meter is a hand-held measuring instrument for acoustic measurements and commonly used in noisy or industrial environments (to help ensure it is within safety standards). (Some people even have the informal version of using apps on their phone so they can see how loud certain environments are).

Which filter network is used for quiet environment?

Filter network A.

Where is there more weighting for (filter network & quiet environments)?

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 where the low frequencies are de-emphazied and the high frequencies are passed efficiently.

Which filter network is used for an environment with a high level of noise?

Filter network C. in C, it is essentially a flat response ike our ear at high sound levels

What is a critical band?

The band in which the sound is "heard" by a HC and connected SGNs. It is the bandwidth of sound being heard by neurons in a channel.

What change occurs across frequency and in relation to which acoustic parameter?

There is a characteristic frequency for a neuron that it responds to, so the critical band has to be within that range in order to be effective. If it is too far away, no masking can be produced. The parameter is intensity, because of the impact of bandwidth on intensity. Within the critical band, the loudness won't change

What happens to the loudness when increasing the bandwidth of the signal to beyond that critical band? Why?

When beyond the critical band, the loudness will increase since he signal level is well above threshold, when it spreads to more than one CB, more auditory channels are activated, so the sound is louder. Neurons in more than one CB is excited; the sound recruits more auditory channels to work and it becomes louder.

What happens when increasing loudness within this critical band?

Loudness won't change within the CB

How can loudness be maintained as the bandwidth changes?

It is like a tradeoff to keep that balance between loudness of equal intensity and the bandwidth - if the bandwidth is increasing, decrease the intensity so that the 'loudness' can be maintained.

What is adaptation?

The sensitivity decreasing during signal presentation and the response to the non-novel signal has a reduced response.

When is sensitivity back?

When there is a new signal.

How is fatigue different than adaptation?

This time, there is a decreased sensation after the signal presentation and it is to all stimuli (versus in adaptation, it is regained for new).

How is adaptation measured?

Loudness matching in which one ear hears a continuous sound and the loudness is matched by presenting a pulsed signal to the other ear and seeing 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 the binaural presentation, (1) large variation across individuals, (2) more significant at only low SL, (3) more at higher frequency (not shown).

The take home message for adaption

Adaptation is level dependent: larger adaptation at lower sound levels and a large variation across individuals.

What is masking?

When one sound interferes the sensation of another sound.

When do we experience masking?

Every day, we want to listen to specific things (someone speaking, or your music as you work out), but we live in a noisy world and there are always competing signals!)

How does masking impact the loudness growth curve?

The threshold (floor) is elevated, the ceiling doesn't change: dynamic range narrower. Therefore the result is a fast growth.

What is loudness recruitment

Steeper growth of loudness with intensity also happens in subjects with sensorineural hearing loss; in such case it is called loudness recruitment; refers to normal rapid grooves and steeped grooves of loudness. Essentially, it means that you can play a sound at a certain intensity and then just increase it a bit, but already that might be too much even if it was just a small change

How is the loudness growth similar to the masking results?

The behavior of the loudness growth in those with sensorineural hearing loss (SNHL) is similar to the masking of normal hearing.

What are 3 reasons that masking is important?

(1) It occurs in our hearing environment and has a great impact on our hearing, (2) it is a useful tool to study hearing, and (3) it has important clinical applications

What does it mean that "masking changes the threshold"?

Masked threshold is usually higher than the threshold in quiet. (i.e., you blast your music louder when you are on the streets or commuting compared to when you are in your own quiet room)

How does masking occur as it relates to the basilar membrane?

There is an excitation pattern that is evident on the basilar membrane. The vibration produced by the masker occupies all auditory channels underneath and all the neurons are excited. Therefore it is an excitation pattern mechanism.