hearing exam6

• 1.Method of Limits
• 2.Method of Adjustment
• 3.Method of Constant Stimuli

• –Stimulus is presented
• –Subject indicates whether or not they heard it
• –Tester manipulates the level of the stimulus based on the subjects response

stimulus level begins below threshold and is raised until the subject can barely hear the tone

• –The subject controls the stimulus level by turning an unmarked knob
• –Stimulus changes in a continuous fashion (rather than in fixed steps)

• Presents various stimulus levels in random order
• •Like the Method of Limits but not sequential
• –No ascending or descending runs
• -Results are tabulated and plotted as a “psychometric function”

• a plot which shows the percentage of times the stimulus was heard at each level
• –Threshold

• -
• Major Approaches to Direct Scaling:
• •Ratio Scales
• •Magnitude Scales

–For example: compared to the standard tone, the comparison tone might be twice as loud

–For example: the subject adjusts the intensity of the stimulus until it is twice as loud as the standard tone

• –A series of stimuli are presented that vary in some dimension such as intensity or frequency.
• –The subject assigns a number to each stimulus to represent its loudness or pitch.

–Physical magnitude adjusted to correspond with numbers indicating perceived magnitude

• Humans have sensitivity over a broad range of frequencies: 10 Hz – 20,000 Hz
• •Hearing sensitivity is best between 2000 – 5000 Hz
• •Hearing sensitivity is poor below 100 Hz and above 10,000 Hz

• based on monaural (one ear) thresholds with earphones
• –Measure sound pressure in the ear canal at threshold

• based on binaural (two ears) thresholds from loudspeakers
• –Measure sound pressure in sound field at head level
• -MAF thresholds tend to be 6 dB lower (better) than MAP thresholds due to binaural summation

• •Sounds become uncomfortably loud at a level of about 100 dB SLP
• –This level is fairly constant across frequencies
• •Sounds that evoke feeling or pain occur at levels of 120 – 140 dB SPL
• –Tactile sensations rather than auditory

• -trading of duration and intensity
• -When sounds are shorter than approximately 300 ms, threshold (or loudness) depends on duration

• •As a sound gets shorter
• –Threshold becomes higher (less sensitivity)
• –The sound is perceived as being softer
• •As the sound get longer
• –Threshold becomes lower (better sensitivity)
• –The sound is perceived as being louder

–a 10-fold decrease in duration is offset by a 10 dB increase in intensity

-the smallest perceptible difference between two sounds

• –ΔI: smallest intensity change that can be detected
• –ΔF: smallest frequency change that can be detected
• -they specify the absolute physical difference needed to tell two sounds apart

• -Weber’s Fraction = absolute DL / starting point
• = ΔI/I or Δ F/F