FINAL EXAM Flashcards
What is Psychoacoustics?
The study of the relationship between the acoustic world and our auditor image of the world:
- How is sound perceived?
- How does perceived loudness relate to sound pressure?
What is sensation?
The awareness of an external stimulus or some change in the body caused by an external stimulus
Example: Loudness, pitch, sound source moving from left to right
What is perception?
Recognizing and interpreting a stimulus based on previous experiences
Example: Speech recognition, voice identification, recognizing a tune
What is the connection between physical stimuli and perception?
Intensity increases= Loudness increases
Frequency increases=pitch increases
Spectral complexity chnages=tibre changes
What is a threshold?
Perceptual: The point where the intensity level of a stimulus Is just large enough to cause a change in the mental response of a person affected by the stimulus
Hearing: lowest sound intensity level at which a listener can barely detect the presence of a sound
What are the 3 types of perceptual thresholds?
1) Absolute Threshold: minimum value
2) Terminal Threshold: Max Value( Uncomfortable loudness)
3) Difference Threshold: Smallest Difference ( You can detect the diff. in pitch, sound, etc)
What are the absolute threshold classifications?
1) Detection Threshold: Sensory
2) Recognition Threshold: Cognitive
What is the threshold of feeling?
Painful sounds to the eardrum
What is the auditory response area?
All the sounds we can hear
What is the threshold of hearing?
-Dependent on lower frequency/duration of a sound
-Lowest sound intensity at which a listener can barley detect the presence of a sound
What is the threshold at 500hz?
look at slide 10 on Nov.8 SS for graph
-200HL
What does this mean?—> it is the softest hearing level they can hear
What is the difference threshold?
-The smallest physical difference between two stimuli in which the listener can determine that two stimuli are perpetually different
-EX: Smallest perceivable change in the pitch of a sound
What is the difference threshold also known as?
- Difference Limen ( DL)
- Just noticeable difference( JND)
What are the detection threshold techniques
- YN(yes-no) technique: Listener responding to yes or no
- N-Alternative Forced Choice(nAFC) Technique : Signal presented–>listener indicates which interval contains the signal
Psychometric Function
- Region Below Threshold: No response
- Threshold region: Responding to it sometimes
- Region above threshold: Intensity is greater, easier to respond
What is signal detection theory?
- (SDT) a method of examining human decisions making in perceptual studies
- Looks at probability( likelihood)
- Considers trials at which are and are not presented
What are the four categories of response:
-HIt: If the signal is presented and the listener responds
- Miss: Signal presented, the listener does not respond
- False Alarm: Signal is not presented, Listener responds
- Correct Rejection: Signal not presented, Listener does not respond
Response criteria/Response bias
Every person develops an internal criterion that dictates how they will respond to a task under conditions of uncertainty
Where do the Yes/No and nAFC techniques originate from?
- Method limits
- Method of Constant (random) Stimuli
- Method of Adjustments
Method of Limits:
- Presenting listeners with the hearing level until they can’t hear it anymore
Benefits: Efficient/Don’t need to know where the threshold is at the start
Limitations: Threshold may be obtained w/o evidence that the listener was really listening
Method of Stimuli:
- Present stimuli to listeners and record the times they report hearing each one
Benefits: Provides a complete picture of sensitivity/Easy to administer
Limitations: Lots of trials, takes time
Method of Adjustments:
- Gives listener control/listener adjusts level until they can just not hear the stimulus
Benefits: Easy to administer/intuitive
Limitations: Potentially unreliable
Difference threshold?
- Intensity
-Frequency
-Duration
In general for people w/ normal hearing, the JND between two frequencies is:
_ Less than 1B
What is loudness?
The property of sound that allows sounds to be ordered on a scale extending from quiet (soft) to loud
Primary dependent on sound intensity
Other factors that impact loudness–> frequency, environment/room you are in, hearing loss, duration of sound
True/False: Our perception of loudness increases as a signal duration increases but only to a certain limit
True
How is stimulus intensity represented in the cochlea?
- In a healthy cochlea, a vibration of a basilar membrane increases with increasing intensity
- In a damaged cochlea, the thresholds are elevated
How is stimulus intensity represented in the auditory nerve?
- different AN Fiber types code for different stimulus intensity levels( high, medium, Low)
- Fibers increase fiberies
- AN Fibers increase firing rate as a stimulus (intensity) level increases
Measuring Loudness:
- Rating the relative loudness of sounds
How loudness changes with intensity - Matching the level of sound to be equally loud as another sound
How loudness changes with frequency
Rating technique for estimating loudness?
- Listener hears a sound
- Assigns number to sound according to perceived loudness
- Resilut= Loudness growth function ( Stimulus level and loudness level)
What is a one sone?
The unit of loudness
Loudness of 40dB at 1,000Hz
Loudness and Intensity: What is considered 2 sones?
Growth of loudness for 1,000Hz pure tones:
- A sound twice as loud would be assigned a value of 2
Loudness and Intensity: What is considered a half-sone?
A sound half as loud would be assigned a value of 0.5
Increasing the level of a sound from 50 to 60 dB SPL?
Loudness goes from two to four sones
For values above 40dB, what happens when you increase the sound by 10dB?
It doubles the loudness
Increase dB level of a sound from 40 to 50 dB SPL, loudness goes from one sone to two stones
Perceive loudness as doubling
What is loudness balancing?
The level of 1000Hz tone in dB SPL is the loudness level of the test sound:
- Measured in phones
- If the reference sound is 40 dB SPL 1000 Hz ton, it would have a loudness level of 40 phones
- If the reference were 70 dB SPL 1000Hz tone, the test sound would have a loudness level of 70 phons
What is Equal Loudness Curve?
Look at Slide 33 from Nov.15th
What are phons?
Unit of measure for loudness level