perception

perception - Massachusetts Institute of Technology...

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Unformatted text preview: Massachusetts Institute of Technology Department of Electrical Engineering & Computer Science 6.345/HST.728 Automatic Speech Recognition Spring, 2010 Guest Lecturer: Louis D. Braida Sensory Communication Group Research Laboratory of Electronics 2/18/2010 Lecture Handouts Auditory Processing of Speech Predicting Speech Intelligibility Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science Figure 1: Long-term spectrum of speech measured in octave or half-octave bands ad mea- sured by Dunn and White (1940). The speech was measured by a pressure microphone located 30 cm from the lips of the talker. Note that a pressure of 1 dyne/sq cm is equal to a pressure of roughly 74 dB SPL. 1 Figure 2: Cumulative distribution of the levels of speech as measured by Dunn and White (1940). The speech was measured by a pressure microphone located 30 cm from the lips of the talker. The output of each octave or half-octave band of speech was squared and integrated for 0.125 s. Note that a pressure of 1 dyne/sq cm is equal to a pressure of roughly 74 dB SPL. 2 Figure 1: Data points and estimated psychometric functions for absolute detection of a 250 Hz tone by a single listener. The left-hand ordinate is the percentage of correct responses. From Watson, Franks and Hood (1972). 1 Figure 2: Estimated psychometric functions for absolute detection of tones of different fre- quencies. From Watson, Franks and Hood (1972). 2 20 40 60 80 100 120 Sound Pressure Level (dB SPL) 20 200 2000 20000 Frequency Threshold of Audibility for Tones Dadson and King, 1952 Yeowart, Brian, and Tempest, 1967 Green, Kidd, and Stevens, 1987 Mean Standard Deviation Figure 3: Absolute hearing thresholds for tones of young adult listeners. Low-frequency thresholds are average values for 10 listeners (Yeowart et al., 1967). Mid-frequency thresholds are median values for 99 men (198 otologically normal ears) in the age range 18-25 y (Dadson and King, 1952). The dotted line is the standard deviation of these thresholds across listeners. High-frequency thresholds are average values for 37 listeners aged 18-26 y (listeners were required to have threshold values of 15 dB HL or less at audiometric frequencies of 8 kHz and less). Only 15 listeners contributed data to the 20 kHz threshold (Green, Kidd, and Stevens, 1987). 3 Figure 4: Minimum Audible Pressure and Minimum Audible Field thresholds reported by Sivian and White (1933). 4 5 Figure 6: Minimum perceptible change in the pressure of 1000 Hz tones at 25 and 50 dB SL as measured by beat detection. From Riesz (1928). 6 0.0 1.0 2.0 3.0 4.0 5.0 Tone Intensity JND (Delta alpha - dB) 20 40 60 80 100 120 Tone Intensity - I (dB SL) Method of Minimum Audible Beats 200 Hz 1000 Hz 8000 Hz Figure 7: Minimum perceptible change in the pressure of tones as a function of frequency and level as measured by beat detection for 4 Hz beats. From Riesz (1928)....
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perception - Massachusetts Institute of Technology...

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