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Questions and Answers
What does Minimum Audible Pressure (MAP) measure?
What does Minimum Audible Pressure (MAP) measure?
Why are MAF thresholds considered better than MAP thresholds?
Why are MAF thresholds considered better than MAP thresholds?
What defines the terminal threshold in terms of discomfort and pain?
What defines the terminal threshold in terms of discomfort and pain?
What is one of the proposed reasons for the 6 dB difference between MAF and MAP?
What is one of the proposed reasons for the 6 dB difference between MAF and MAP?
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How does dynamic range vary according to sound frequency?
How does dynamic range vary according to sound frequency?
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Which statement accurately describes high sensitivity units in auditory nerves?
Which statement accurately describes high sensitivity units in auditory nerves?
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What key factor eliminates the 6 dB difference when calibrating MAP and MAF?
What key factor eliminates the 6 dB difference when calibrating MAP and MAF?
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What does the concept of dynamic imply in relation to sound levels?
What does the concept of dynamic imply in relation to sound levels?
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What is the main focus of understanding the MAF and MAP difference?
What is the main focus of understanding the MAF and MAP difference?
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What statistical method is used to determine the auditory threshold?
What statistical method is used to determine the auditory threshold?
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What has recent research suggested about the 'missing 6 dB problem'?
What has recent research suggested about the 'missing 6 dB problem'?
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What measurement approach is often impractical according to the content?
What measurement approach is often impractical according to the content?
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Why are terminal thresholds less clear or accurate in their definitions?
Why are terminal thresholds less clear or accurate in their definitions?
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What is the Reference Equivalent Threshold SPL (RETSPL) related to?
What is the Reference Equivalent Threshold SPL (RETSPL) related to?
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What does the 50% correctness point indicate in determining the auditory threshold?
What does the 50% correctness point indicate in determining the auditory threshold?
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What is the primary characteristic of low sensitivity auditory units?
What is the primary characteristic of low sensitivity auditory units?
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What does loudness primarily refer to?
What does loudness primarily refer to?
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How is loudness largely affected?
How is loudness largely affected?
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What does the term 'SL' refer to in loudness measurements?
What does the term 'SL' refer to in loudness measurements?
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If a 1000 Hz tone at 40 dB is defined as 1 sone, what would doubling the loudness yield?
If a 1000 Hz tone at 40 dB is defined as 1 sone, what would doubling the loudness yield?
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What change in decibels (dB) typically results in a doubling of perceived loudness?
What change in decibels (dB) typically results in a doubling of perceived loudness?
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Which graph demonstrates a steeper curve indicating a rapid increase in loudness with intensity?
Which graph demonstrates a steeper curve indicating a rapid increase in loudness with intensity?
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In the relationship between loudness and intensity, which equation is used to describe this relationship?
In the relationship between loudness and intensity, which equation is used to describe this relationship?
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Which of the following best describes the term 'sone'?
Which of the following best describes the term 'sone'?
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What is the function of the critical band in auditory perception?
What is the function of the critical band in auditory perception?
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How does the critical band relate to the central frequency?
How does the critical band relate to the central frequency?
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Which type of masking is likely due to memory interference?
Which type of masking is likely due to memory interference?
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In clinical settings, which type of noise is most efficient for masking?
In clinical settings, which type of noise is most efficient for masking?
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What occurs in backward masking?
What occurs in backward masking?
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Which statement regarding monotic and dichotic masking is correct?
Which statement regarding monotic and dichotic masking is correct?
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What phenomenon causes stronger masking effects when the signal is closely timed to the masker?
What phenomenon causes stronger masking effects when the signal is closely timed to the masker?
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Which masking type is associated with the masker and probe being in different ears?
Which masking type is associated with the masker and probe being in different ears?
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What does Weber's Law state regarding the smallest detectable difference (∆I)?
What does Weber's Law state regarding the smallest detectable difference (∆I)?
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What is the just noticeable difference (JND) for pure tones in decibels?
What is the just noticeable difference (JND) for pure tones in decibels?
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If the original intensity (I) is 10 units and the smallest detectable difference (∆I) is 0.5 units, what is ∆I when I is 1000 units?
If the original intensity (I) is 10 units and the smallest detectable difference (∆I) is 0.5 units, what is ∆I when I is 1000 units?
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Which of the following statements about intensity discrimination is true?
Which of the following statements about intensity discrimination is true?
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How does ambient noise affect earphone testing?
How does ambient noise affect earphone testing?
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What characterizes Weber's fraction in terms of intensity discrimination?
What characterizes Weber's fraction in terms of intensity discrimination?
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What does the formula ∆I in dB = 10 log (1 + ∆I/I) represent?
What does the formula ∆I in dB = 10 log (1 + ∆I/I) represent?
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What does it mean when Weber's Law shows that the plotted relationship between ∆I/I is not a straight horizontal line in real-life experiments?
What does it mean when Weber's Law shows that the plotted relationship between ∆I/I is not a straight horizontal line in real-life experiments?
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What is the result of a 10 dB change in sound pressure level?
What is the result of a 10 dB change in sound pressure level?
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How is intensity related to pressure according to the content provided?
How is intensity related to pressure according to the content provided?
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What does a 10x increase in intensity lead to in terms of pressure?
What does a 10x increase in intensity lead to in terms of pressure?
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What does the phon scale reference for loudness measurements?
What does the phon scale reference for loudness measurements?
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What is the threshold of hearing described in the content for SPL variations at low levels?
What is the threshold of hearing described in the content for SPL variations at low levels?
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What relationship does a 10 dB change have with intensity?
What relationship does a 10 dB change have with intensity?
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What happens to the equal loudness contours at high sound pressure levels?
What happens to the equal loudness contours at high sound pressure levels?
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What does the dynamic range measure in sound levels?
What does the dynamic range measure in sound levels?
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Study Notes
Psychoacoustic Introduction
- Psychoacoustics is the study of how we perceive sound, the psychological side of hearing science.
- It forms the foundation of hearing science, closely related to psychophysics.
- Psychoacoustics studies how sound affects behavior and perception.
- Psychophysics studies how sound behaves and its properties.
- The relationship between sound stimuli (S) and behaviours (B) can be qualitative, descriptive, or quantitative.
- Behavior is the starting point and end goal of neuroscience.
- Initially, the brain is treated as a "black box."
- Later, researchers identify the brain structures responsible for specific behaviors.
- Hypotheses are created to explain behaviors and are tested quantitatively.
- Psychological, neurological, and molecular experiments uncover the mechanisms behind behavior.
- Over time, theories are developed to better explain behaviors and improve people's lives.
Psychoacoustic Function
- S: Sound properties (Intensity, Frequency contents, Temporal patterns)
- B: Behaviors (Loudness, Pitch, Temporal patterns, Timbre: a combination of frequency and intensity changes over time, High Level processes: i.e., the recognition of speech).
- F: Functional relationships (between S and B) (Detection, Discrimination, Identification, Judging (scaling)).
Analytical Studies
- Individual acoustic parameters (intensity, frequency, and temporal patterns) play important roles in sound perception.
- Acoustic parameters are detected, discriminated, identified, and scaled (quantified)
Integrative Studies
- The brain integrates the response to individual acoustic parameters to improve the perception of information.
- Integration involves neurons across different auditory channels, different neuron types, different nuclei, and balances excitation and inhibition as well as afferent and efferent pathways.
- Examples of integration in psychoacoustics include sound localization and auditory perception.
- Auditory perception creates an acoustic image from a complex environment using various cues like memory and prior experiences.
Dimensions of Auditory Ability
- Absolute limen: the lowest boundary of detection (sensitivity or minimum)
- Terminal limen: the upper boundary of detection (maximum or limitation)
- Difference limen: the smallest change in a stimulus that can be detected
Sensitivity and Limitation
- Sensitivity: absolute thresholds for sound intensity/pressure.
- Minimum Audibility Curves: sensitivity across the frequency range, shown in an audiogram.
- Frequency Range of Hearing: limits of the hearing spectrum at low and high frequencies.
- Terminal Thresholds: defined by threshold of discomfort and threshold of pain.
- High sensitivity means a low threshold.
Dynamic Range of Hearing
- Two thresholds define dynamic range.
- Loudness changes with sound level changes.
- Dynamic range varies with frequency.
- Terminal threshold curve is flat.
- Audibility curve is curved.
- Variation of the independent variable results in a change of dependent one.
Comparison on To the Dynamic Range of Auditory Nerves
- High SR units are best for picking up soft sounds, but they saturate quickly with louder sounds.
- Low SR units are less sensitive to soft sounds, but can easily handle louder sounds without saturating.
Hearing Area (Defined by Sound Level and Frequency)
- Terminal thresholds are defined in different ways.
- They are less clear or accurate and less studied due to ethical reasons.
Threshold is Determined Statistically
- Multiple trials are tested at each level to calculate the percentage of correct responses.
- The threshold is statistically found based on percentage of correct responses at a chosen criterion (e.g. 50%).
- Threshold represents the noise level when hearing begins.
Variability and Reliability
- Many factors besides ability affect performance (using statistics).
- Variability: differences in hearing thresholds among individuals (e.g., 10–20 dB for normal hearing adults).
- Test-retest reliability: variation in hearing thresholds for the same person tested multiple times (e.g., 10–15 dB).
- Range is provided to account for variability and reliability.
The Meanings of the Variations
- Normality is defined as a range.
- The range depends on testing methods and the tester's skill.
- Variation of 10–15 dB is considered normal for test-retest reliability.
- Additional training may be needed if performance is worse than normal.
- This range helps determine if hearing loss is present.
- Criteria are used to judgment if someone has hearing loss
The Open V Shape of Absolute Threshold
- The graph shows data from various studies, which all demonstrate a similar open "V" shape.
- The curve is measured at different frequencies, all of which show a similar trend.
How is the Audibility Curve Shaped?
- External and middle ears shape the audibility curve.
- Frequency response of external and middle ears affects hearing sensitivity.
Contribution of the Cochlea
- External and middle ears don't entirely explain hearing sensitivity; the cochlea contributes.
- Bone conduction bypasses external and middle ear and tests cochlear function directly.
- Bone conduction doesn't provide a flat frequency response.
Minimal Audible Field (MAF) vs. Minimal Audible Pressure (MAP).
- MAF is measured with speakers in an open field and calibrated at 1 meter
- MAP is measured in a closed field (with headphones), and SPLs are measured with a coupler.
- MAF thresholds are better (lower) than MAP thresholds, by 6–10 dB.
Early Theories of the 6dB Difference
- Research conducted from 1960 to 1970 showed three possible reasons for the 6 dB difference:
- The natural boost from the outer ear is removed in the MAP method.
- Binaural summation (using both ears in MAFs) is more efficient than the MAP method.
- The possibility that MAP may pick up physiological noise (internal body sounds).
MAP = MAF?
- Yost and Killion (1997) reviewed this issue and found no actual 6 dB difference when measuring hearing with real ears rather than just the coupler method.
Why Should We Care About the MAF and MAP Differences?
- Real-ear calibration isn't always possible.
- Understanding the differences between MAF and MAP helps correctly interpret hearing data.
- This helps in establishing sound-level references.
Reference Equivalent Threshold SPL (RETSPL)
- Sound pressure is measured using a coupler or a space without human subjects.
- Coupler pressure is established for a consistent reference across labs.
- RETSPL is established and verified globally for use with couplers.
- The head's contribution isn't considered in RETSPL.
6-CC Coupler for Supra-Aural Earphones and 2-CC Coupler for Insert Earphones
- Types of couplers used for measuring sound from earphones and inserts
- Simulate ear canals
- Measurements are made using a microphone.
RETSPLs: Data and Applications
- Tables present RETSPLs for earphones, and bone vibrators.
- RETSPLs represent thresholds (sound pressure levels), needed for the hearing threshold.
- Applications include calibration references for speakers and earphones, establishing hearing levels using RETSPLs (setting the zero point for 0dB HL), noise allowance standards.
Why Using HL?
- SPL: Reference for physical sound pressure (e.g. 20 µPa).
- HL: Reference for hearing thresholds of normal subjects using RETSPL. •SL: (Sensation Level): a reference based on individual hearing thresholds.
Application of RETSPL
- RETSPL is crucial for calibrating audiometric equipment.
- It ensures devices accurately reflect real hearing thresholds in decibels.
- Control of ambient noise which is below RETSPL.
Intensity Discrimination
- Weber's Law: A change (∆I) that's perceivable is proportional to the initial intensity (I) (∆I/I = constant).
- Weber's fraction (∆I/I) measures how well we can perceive differences in intensity.
- The just noticeable difference (JND) is expressed in dB.
Converting Weber's Fraction to dB
- Weber's fraction (∆I/I) is expressed in decibels ∆I in dB = 10 log (1+∆I/I)
- Doesn't change based on starting intensity, i.e. the 1db difference is always constant.
Intensity Discrimination Result: Not Quite a Horizontal Line
- The intensity discrimination threshold for narrow band or tones is approximately 1 dB
Near Miss of Weber's Law
- Weber's law is close to accurate but not perfect, especially for pure tones.
White Noise Follows Weber's Law More Closely Than Tones
- Intensity discrimination works better for broadband signals (white noise).
- The discrimination threshold is smaller for white noise than for pure tones.
Method Considerations
- Several methods are used for measuring thresholds for intensity discrimination.
- Results vary depending on the chosen methods (gated pulse tone, continuous tone, and modulation tone, i.e. pedestal).
Gap-Detection Threshold as a Function of Sensation Level (SL)
-Two methods are used: Continuous pedestal(better results) and Gated methods -Higher sensation levels improve gap detection.
Summary of Factors Affecting Intensity Discrimination
- Bandwidth, Frequency, Sound Level, Duration (not addressed), and Testing Methods
Loudness Sensation
- Loudness refers to the perception of sound intensity, influenced by sound level, frequency, duration, and other sounds.
- Loudness is subjective, measured through behavioral tests.
Loudness Scale
- 800 Hz tone at 100 dB SL ≈ 100 arbitrary units
- Half the loudness = 50 arbitrary units
- Doubling the loudness = 200 arbitrary units.
Pay Attention to Scaling Methods
- Loudness is related to sound level, using intensity (in dB SL).
- Graphs show the relationship using different units (relative sound pressure).
Note for the Previous Slide
- SL (Sensation Level): A measure of intensity relative to an individual threshold.
- Be cautious about visual memory of the graphs, as it can be misleading.
Sone Scale
- 1000 Hz tone at 40 dB is defined as 1 sone.
- Doubling or halving loudness results in 2 or 0.5 sones.
- Relation between sone loudness and intensity follows a power function (e.g., sone loudness = kI0.3).
A 2x Change in Sone Corresponds to a 10dB Level Change
- A 10 dB increase in intensity results in doubling the loudness.
- A change of 10 dB in sound pressure level (SPL) corresponds to a doubling in loudness.
Converting Intensity (I) to Pressure (p)
- Intensity (I) relates to pressure (p).
- A 10 dB change in sound pressure results in a 2x change in loudness.
A 10 dB Change in Intensity Results in a 2x Change in Loudness
- 10 dB increase in intensity results in doubling perceived loudness (except at low SPLs near hearing threshold).
Equal Loudness Contours
- Phon scale uses 1000 Hz as a reference point
- Matching intensities of different frequencies at equal loudness
- SPL needs to change at other frequencies to ensure equal loudness
How Contour Shapes Change with Sound Level
- At low SPLs, the SPL required for equal loudness varies greatly with frequency.
- At high SPLs, variations across frequencies are smaller and contours are flatter.
Impact of Contour Shape on Dynamic Range and Loudness Growth
- Dynamic range measures the difference between the lowest and highest SPLs.
- The 1000-4000 Hz range has the largest dynamic range and faster loudness growth.
- Dynamic ranges vary with low and high frequencies.
Note: Loudness Growth Function
- Loudness increases with sound level.
- Flat contour (at high sound levels), equal ceiling and floor.
- Curved contour (at lower sound levels), the floor is equal to the ceiling as intensity increases.
- "Faster" means a change in loudness given a change in SPL.
How Loudness Contours Affect the Perception of Sound
- Boomy: excessive low-pitch sound; playback is louder than the recording (low frequencies).
- Tinny: excessive high-pitch (crisp) sound; playback is quieter than the recording (high frequencies).
Filter Settings of Sound Level Meters
- Filter A for quieter sounds, emphasizing mid-range frequencies.
- Filter C for louder sounds, treating all frequencies more equally.
- Filter B is an intermediate filter.
Filter Networks Used in Sound Level Meters
- dB A: used for measuring sound in quiet environments.
- dB C: used for measuring high-level noise.
Concept of the Critical Band
- Critical band (CB) is a range of frequencies a hair cell and its connected spiral ganglion neurons are sensitive to.
- The CB relates to the tuning curves of auditory nerve fibers (ANFs).
Key Concepts: Critical Band (CB) & Psychophysical Tuning Curve (TC)
- Critical Band (CB): The frequency range a hair cell and its neurons are sensitive to.
- Psychophysical Tuning Curve (TC): The curve shows how different frequencies are heard by the ear.
Critical Band (CB) Defined by Masking.
- Masking tuning curves.
- When broadband noise is used as a masker, only energy in a specific frequency range is effective. The range is the Critical Band.
Critical Band (CB) Continued.
- Critical band (CB) is proportional to the central frequency, it is approx 1/3 of an octave on most sound measures. -Noise is most effective in 1/3 octave bands.
Key Concepts
- Critical Band (CB): A frequency range where a sound is perceived.
- 1/3 octave noise is most efficient as a masker in clinical settings.
Temporal Masking
- Masking can occur at different time relationships between the masker and the signal: forward, simultaneous, backward.
Explanations of the Pictures of Different Masking Types
- Graphs illustrate the various types of temporal masking(backward, forward and simultaneous).
- Maskeer signals are presented at different time intervals with respect to the test stimulus
Key Points About Previous Slides
- Closer spacing between masker and signal = more masking effect.
- Monotic (same-ear) masking is more effective than dichotic (different-ear) masking.
- Backward masking is likely due to memory interference, not interaction in the cochlea.
Informational/Central Masking
- It does not involve energetic interaction in the cochlea.
- It's more about content confusion; there only needs to be informational similarity between masker and signal.
- Central masking occurs when the masker and signal are presented to different ears.
- No frequency overlap is needed for informational masking; there only needs to be informational similarity.
Key Concepts
- Informational and central masking are independent; the former has no requirements for frequency overlap between masker and signal, unlike the latter.
- Informational masking occurs when the brain confounds the content of a masker and signal; thus, no frequency overlap is required.
- Central masking occurs when a masker and signal are presented to opposite ears.
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Description
Test your knowledge on key concepts related to Minimum Audible Pressure (MAP) and Maximum Audible Frequency (MAF). This quiz covers auditory thresholds, dynamic range, and the intricacies of sound perception. Dive into the research and principles that shape our understanding of auditory measurement.