Mcq Flashcards
What are the perceptual and physical characteristics of hearing?
Perpetual-Loudness Physical- intensity SI
Perpetual- Pitch Physical- Frequency SI (hertz)
What are the two dimensions of pitch?
Height- going from low to high
Chroma- which describes the similarity of the note
What is Timbre?
A perceptual characteristic of sound
Can be described as dull, bright, warm
Timbre sometimes referred to as quality of music
What are such perceptions that we can quantify and ask how much called? E.g. One light twice as bright
Prosthetic continuum
Perceptions when you can not put a value on stimulus are called?
E.g. It doesn’t make sense to ask if a red hue is more or less than green hue
Metathetic continum
The difference that can be detected in 50% of trials is referred to as?
JND just noticeable difference
or Difference threshold
What is the absolute threshold?
Related to single stimulus, the level where the stimulus can just be detected as being present
E.g. From nothing to first hearing sound
Related to detection
Lowest level of an auditory stimulus that is audible
( usually sinusoidal simulation-pure tones)
What is the difference threshold?
JND smallest difference between stimuli that can be discriminated
Smallest change in stimulus which a person can detect 50% of the time.
What is the point of subjective equality PSE
Point
Subjective
Equality
Equal (perceived)
Point of comparison where stimulus is judged or perceived to be equal to standard stimulus
What is POE
Point of
Absolute
Equality
Equal (objective)
POE
The point where a comparison stimulus can actually be measured to be equal
Detection of an acoustic signal is related to?
Sensitivity
The
Detection threshold +
Difference threshold (JND)
Are inversely related to?
The absolute sensitivity
Therefore the greater the absolute sensitivity the lower the detection threshold
E.g. The better detecting something there
What is detection
Determine if present or not
Can be considered case of discrimination
Can you distinguish (discriminate) the stimulus from no stimulus
What is discrimination?
Ability to DETECT DIFFERECE between one signal and another i.e. Tell the difference between frequencies and intensities. in sound
The difference threshold is inversely related to the DIFFERENTIAL SENSITIVITY
The greater the differential sensitivity the lower the difference threshold
(Better at detecting difference between or discriminate between stimuli)
Methods of measuring sensitivity to a stimulus
Method of adjustment?
Simplest method of finding a stimulus threshold is to ask a participant to adjust the sound level with a dial until they can just detect the presence of the stimulus
Can be used to measure RELATIVE THRESHOLD
METHOD OF ADJUSTMENT
Final threshold value depends on if threshold is approached from above or below(start well belo/above)
Methods of measuring sensitivity to a stimulus
Method of limits?
Tester controls intensity
At each intensity participant presses a button if they can perceive the stimulus
Advantages quick, can be used with AFC or 2AFI. Duration under control of tester
Negatives- poor trials
Methods of measuring sensitivity to a stimulus
Method of constant stimuli
Stimulus presentation doesn’t depend on participant response
Randomised
Usually automated
Think hearing tests I did in military
Measures of absolute threshold
Minimum auditory field (MAF)
MINIMUM AUDITORY FIELD (MAF)
Sounds played in FREEFIELD
Presented over loudspeaker in a anechoic chamber
Listener usually 1m away
Calibration of SPL doesn’t account for body
Measures of absolute threshold
Minimum auditory pressure
MINIMUM AUDITORY PRESSURE (MAP)
Sounds played over HEADPHONES and minimum audible pressure is measured at the tympanic membrane TM
Measured SPL
Usually monaural
Headphones don’t account for head diffraction, ear canal resonance etc
Position of probe microphone affects measurements at high frequencies (standard waves)
Measures of absolute threshold
Hearing level
HEARING LEVEL (HL) Measure based on estimate of minimum audible pressure at TYMPANIC MEMBRANE (TM)
What range of frequencies does the unmanned ear “hear”
20Hz to 20kHz
Most sensitive over mid frequencies 1to4kHz
At 1kHz the normal threshold is about 0dB SPL or 20uPa.
Why do we measure in RETSPL?
Not MAP or MAF
They are difficult and time consuming. So we use: RETSPL
Reference
Equivalent
Sound
Pressure
Level
For the particular headphones and measure the threshold relative to that for young ontologically normal listeners. That is a hearing level (dB HL)
What is acoustic intensity measured in?
W/m2
Where Wis the power in watts
Power=energy/time
What is Criterion?
Influencing factors
Bias
Signal detection responses
Hit
Cx correctly reports signal when it IS present
Signal detection responses
Miss
False negative
Cx reports signal is NOT present when it IS
Signal detection responses
False Alarm
False Positive
Cx reports signal is present when it is NOT present
Signal detection responses
Correct rejection
Cx correctly reports signal is not present when it is not present
What is auditory closure
The ability to complete indistinct or inaudible words to complete a clear auditory image
(Only half hearing a word sorting through sentences to make sense)
What factors will affect signal detection/ discrimination
Criterion
Background noise(=lower SNR) Signal strength Redundancy (amount of repeats of signal) Quality Reliability
What is Webers law?
The bigger the stimulus, the bigger the increment needed for a change to be detectable.
What is phase locking?
When peaks of excitation synchronise to the stimulus around 4Khz
Difficulties in listening environments
Background noise low SNR
Stimulus variable of background noise
Speaking communication tactics poor e.g. Covering mouth with cup
Reflective surfaces (sound bouncing reverberating reinforcing background noise)
Echo
Making own voice louder (distortion)
Distance from speaker due to tables/seating
Upwards spread of masking=high
Traffic noise from door
Noisy coffee machines
Difficulties listening to a chosen voice?
Frequency of voice Accents Level of voice intensity (can be lowered especially at end of stances) Familiarity of voice Upward spread of masking
Communication tactics in noisy environment s (sciences)
Sit in corner (+ SNR)
Face speaker
Close to sound source (increase SNR increase frequency selection) inverse square law
Don’t cover face
Sit away from kitchen/doors
Auditory scene by using other senses to visualise
What is Diotic hearing?
Binaural hearing is diotic if identical sounds are presented to both ears
What is dichotic hearing?
Contrast to diotic listening to something different one side to another
What is binaural fusion/integration?
Process by which the sounds are fused into a coherent image. Sounds from both ears put together
Related to frequency
What is binaural summation?
Sounds put together from both ears related to intensity.
Drawbacks of stenger test
Takes a long time Tires patient Patient can cotton on to test Doesn't find actual threshold Needs to be compared to other tests such as reflex testing
What is localisation
.
What is lateralisation
.
Head shadow effect discuss
.
Pinna effect explain?
.
What is a conservative responder
E.g. Of what ROC curve would be like
Cautious responder prone to not responding More misses
More correct rejections
What is a liberal responder?
Effects on ROC curve?
Prone and open to responding to the stimulus.
More hits
More false alarms
Equal distribution of hits and false alarms on ROC curve indicates liberal responder
What is a ROC curve
Receiver
Operating
Characteristics
Plots HITS against FALSE ALARMS
Top two boxes
What is a balanced responder
E.g. Of ROC graph
Equal distribution of
False alarms
Misses
What is a ROC graph?
Red lines = signal absent Blue lines= stimulus Threshold shown by dotted line Coloured blue= hit rate False alarm= shaded red D prime = area in grey between two peaks
ROC graphs related to liberal/ conservative responder
Opposite of politics
Greater shaded area to right= liberal
Greater shaded area to left= conservative
Balanced both parts equal
What is D prime
A statistical tool
Can reduce bias
Separates sensitivity from willingness to respond
Provides a measure of the observers sensitivity to detect weak signals
What is psychoacoustics?
Study of relationship between the PHYSICAL CHARACTERISTICS of STIMULI and our psychological perception of them.
