Midterm Loudness Flashcards
Loudness
The perception of intensity
How to determine if tones of different freq are the same loudness
Equal loudness contours- Subject asked to match loudness of the the test tone to a frequency tone of 1kHz
Phons
Unit of loudness at 1kHz Equal to 1 dBSPL Compares a test tone to a reference tone Flattens out as intensity increases Equality of loudness
A weighting of phons
Mimics 30-40 phon scale
Deemphasizes low at low intensity
B weighting of phons
Mimics 70 phon scale
Deemphasizes lows at low intensity
C weighting of phon scale
Mimics 100 phon scale
Flatter responses
How to assess loudness
Magnitude estimation
Magnitude production
Sone scale
Magnitude estimation
Subject decides how loud a stimulus is in reference to another perceived loudness
Magnitude production
Subject adjusts stimulus to reach a specified loudness
Sone scale
Developed by S.S. Stevens in 1955 Unit of loudness referencing 40 phons Gives a ratio of loudness Loudness scaling 10 dB inc= doubling of loudness perception
Factors affecting loudness
Noise Binaurality Freq Duration Adaptation Complexity of signal Loudness recruitment Auditory fatigue
How does noise affect loudness
In background noise, a dec. in loudness will be perceived even with no change in intensity
Noise will inc threshold of detection & loudness growth
Who developed the loudness curve
Zwislocki in 1964
How does Binaurality affect loudness
Inc the perceived loudness of a stimulus
Monaural is 1/2 as loud
How does freq affect loudness
The dynamic range is different at different freq
Wider at 1kHz
800 to 5000 the growth of loudness mimics 1kHz
Below 800 and above 5000 the growth of loudness inc rapidly
How does duration affect loudness
Loudness grows quickly within the first 200 msec
After the first 200 msec the perception of loudness remains constant
Shorter durations require higher intensity to achieve equal loudness
Adaptation
There is apparent decrease in loudness of a signal that is continuously present at a fixed level
4 basic truths about adaptation
- There is a noticeable variability among people in terms of how much adaptation occurs
- Loudness of a pure tone adapts when presented at levels up to 30 dBSPL, then it tends to flatten out
- There is more adaptation at high-frequency then low-frequency
- Adaptation is about the same one presented monaurally vs binaurally
How does the complexity of the signal affect loudness
Complex tones are often perceived to be louder than pure tones of equal SPL
Loudness depends upon spectral characteristics
Energy summation
Accounts for loudness perception of complex stimuli when energy is concentrated within a critical band
Loudness summation
Accounts for loudness perception of complex stimuli when energy is distributed outside a critical band
Loudness recruitment
Abnormal rapid growth of loudness with increased intensity
How to test for loudness recruitment with unilateral losses
Use magnitude production
How to test for loudness recruitment for bilateral losses
magnitude estimation
Normal results for loudness recruitment testing
Produce loudness matching function with slope close to 1.0
Unilateral results for loudness recruitment testing
Cochlear losses produce slopes much greater than 1.0
Bilateral losses results for loudness recruitment testing
Cochlear losses produce slopes greater then 1.0
Similar pattern to unilateral losses
Why does loudness recruitment occur
Loss of neurons that detect weak stimuli, but not loud ones, increased neural firing rate at high-intensities
Tests to use for loudness recruitment
SISI- Short increment sensitivity index, Slight increase in intensity at some point during the stimulus
ABLB- Alternating binaural loudness balance, Present reference and comparison tones to both ears, determine differences between ears
UCL- Patient presented with loud stimuli to determine when a stimulus is too loud
Auditory fatigue
The temporary loss of sensitivity to a stimulus after exposure to another stimulus
During fatigue system is incapable of responding or requires more energy
What is auditory fatigue dependent on
Intensity of stimulus
Duration of stimulus
Frequency of stimulus
Auditory fatigue initial recovery
Recovery process occurs within first minute, this process only last for that long, secondary recovery occurs later
Auditory fatigue metabolic recovery
Compound action potential larger after fatiguing stimulus, oxygen supply greater in cochlea
