Methods of Hearing Threshold Measurement Flashcards
what is the method of constant stimuli
Present various stimulus levels with preselected step size but presented in random order, this is a non sequential procedure.
How do you deal with the response bias in the method of constant stimuli
-You can include catch trials which are trials when no stimulus is presented and the percent of “yes” responses are tracked. This permits estimate of guessing
What are the pros and cons of the method of constant stimuli
Pros: Greater precision than MOL and MOA, and permits direct estimation of guessing
Cons: Slow! And need a large number of trials (time and fatigue)
What are the modern methods of hearing threshold measurement
Forced choice method, adaptive procedures, Von Beskey method, Simple Up Down and ASHA 2005
Describe the Forced Choice Method
Two alternative forced choices- presented with two stimuli in succession and asked to choose the one that matches the criteria.
Example: two noise stimuli, one of which also contains a pure tone – 2AFC task is to listen to each stimulus and then identify which presentation had the tone
Describe the Adaptive Procedures method
Tester adapts to the level of stimulus presentation depending on how the subject responds to the previous stimulus. The goal is to converge quickly toward the threshold, then obtain most of the observations around the point. Here we start with large step size and adjust it smaller as we near threshold
Describe Von Bekesy’s Tracking Method:
Includes aspects of classical method of limits and adjustment with adaptive procedures
Subject controls stimulus presentation intensity level- Subjects must press the button while they are hearing the tone and release it while they can’t hear the tone
◼ Level changes at a fixed rate (e.g., 2.5 dB/sec), decreasing as the subject holds down button, increasing with release. Threshold = average of stable midpoints
What are the pros and cons of the Von Bekesy’s Tracking Method:
Pros: Speed, precision
Cons: Response biases- at faster intensity rate changes by the time the subject’s reaction time kicks in, level will have changed too much. As slower rates of intently change, subjects criterion for threshold tends to vary
Describe the Simple Up Down Method
Increase stimulus level if subject did not respond to previous stimulus, decrease it if he/she did
Similar to MOL: experimenter changes stimuli in discrete steps
Different from MOL in that each run does not start from a fresh intensity level, but rather continues from the point of reversal – similar to von Békésy, but here the experimenter has control and change happens in steps, not continuous. Threshold = average of stable midpoints, or average of peaks and troughs
Run ~ 6 – 8 reversals and can do further runs
with smaller steps for better precision
What are the pros and cons of the Simple Up Down Method
Pros: Precision- can start with large step size and decrease on follow up runs. Speed: quickly converges on threshold so most trials can focus close to threshold
Cons: If step size is set too small, larger number of wasted trials, but if too large – decreased precision. ◼ Can only converge on the 50% point (vs. 75%, etc.)
Describe the ASHA 2005 Method
Begin well below expected threshold (e.g., -20 dB HL)
Increase by 5 dB per trial until + response
Then decrease by 10 dB and start another ascending run in 5 dB steps
-Threshold defined as lowest dB HL at which responses occur in at least half of a series of ascending trials- Order: 1000, 2000, 3000, 4000, 6000, 8000, 1000, 500, 250, 125 Hz
