# hearing exam6

 Classical Measurement Methods 1.Method of Limits 2.Method of Adjustment 3.Method of Constant Stimuli Method of Limits –Stimulus is presented –Subject indicates whether or not they heard it –Tester manipulates the level of the stimulus based on the subjects response Run: Number of individual presentations of a stimulus –Ascending run: stimulus level begins below threshold and is raised until the subject can barely hear the tone Method of Adjustments –The subject controls the stimulus level by turning an unmarked knob –Stimulus changes in a continuous fashion (rather than in fixed steps) Method of Constant Stimuli 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” –Psychometric Function: a plot which shows the percentage of times the stimulus was heard at each level –Threshold Direct Scaling subject establishes the relationship between a standard and comparison stimulus -Major Approaches to Direct Scaling: •Ratio Scales •Magnitude Scales Ratio Estimation: expresses subjective magnitude of one stimulus as a ratio of the other stimulus –For example: compared to the standard tone, the comparison tone might be twice as loud Ratio Production: adjusts the magnitude of a stimulus to produce a specific ratio of the other –For example: the subject adjusts the intensity of the stimulus until it is twice as loud as the standard tone Magnitude Estimation: –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. Magnitude Production: –Physical magnitude adjusted to correspond with numbers indicating perceived magnitude Human Hearing Thresholds 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 1.Minimum Audible Pressure (MAP): based on monaural (one ear) thresholds with earphones –Measure sound pressure in the ear canal at threshold Minimum Audible Field (MAF): 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 Upper Limits of Hearing •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 Temporal Summation/Integration def -trading of duration and intensity -When sounds are shorter than approximately 300 ms, threshold (or loudness) depends on duration Temporal Summation/Integration •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 integration –a 10-fold decrease in duration is offset by a 10 dB increase in intensity Just Noticeable Difference (JND) or Difference Limen (DL): -the smallest perceptible difference between two sounds Absolute Difference Limens: –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 Relative Difference Limen or Weber Fraction: -considers both the absolute DL and the starting point -Weber’s Fraction = absolute DL / starting point = ΔI/I or Δ F/F AuthorAnonymous ID52318 Card Sethearing exam6 Descriptionexam 6 Updated2010-11-30T03:21:18Z Show Answers