Calibration of Consonant Perception in Room Reverberation K. Ueno (Institute of Industrial Science, Univ. of Tokyo) N. Kopčo and B. G. Shinn-Cunningham (Hearing Research Center, Boston Univ.)

Introduction  Our auditory process is usually assumed to be static and fixed, dependent only on the input signals rather than on the state of the listener.  We naturally and fluidly compensate for many interfering effects in everyday environments.  How do listeners calibrate auditory perception to acoustic interference?

Outline of the Study  PURPOSE: To explore how listeners calibrate auditory perception to room reverberation.  STRATEGY: Measure the effect of sudden changes of reverberation on speech perception. Carrier phrase (Rev C ) Target (Rev T ) Carrier phrase (Rev C ) --- Lower performance Un-matching reverberation --- Higher performance Matching reverberation  HYPOTHESIS: Consonants identification performance should be better when listeners have consistent room experience just prior to a test sound.

Stimuli VC1 VC VC * Rev-C *Rev-T Carrier phrase Target  Speech source: VC (Vowel-Consonant) syllables with 16 consonants preceded by ‘o’ (/a/) ok, ot, op, of, od, og, ob, ov, oth(v), om, on, ong, oz, oth(uv), os, osh Two male and One female Recordings from corpus and a past study  Binaural room IR (BRIR): R1, R2, Anechoic  Test sound: VC*BRIR

Binaural room impulse responses R1: at relatively closer point (12m) to the sound source in very reverberant church. … reverberant R2: at second balcony in a large concert hall (33m) … reverberant Pseudo-anechoic BRIR are processed from R1 BRIR by a 5-ms time window. … dry (clear) R1,Lch R2,Lch

R1 R2

Binaural room impulse responses R1: at relatively closer point (12m) to the sound source in very reverberant church. … reverberant R2: at second balcony in a large concert hall (33m) … reverberant Pseudo-anechoic BRIR are processed from R1 BRIR by a 5-ms time window. … dry (clear) R1,Lch R2,Lch Processed for Pseudo-Anechoic HRTF

Experimental Design and Procedure  Test signals were presented with insert headphones.  Subject’s responses for the final VCs were obtained by GUI using 16 graphical buttons labeled with the VCs.  Number of VCs (2 or 4) in the carrier was fixed throughout blocks of trials.  Stimuli set (10 VCs x 3 talkers x 3 conditions = 90 trials in total) were randomly presented in each block, repeated twice for each subject.  Subjects: 14 Native English speakers  Percent-correct target identification scores were calculated for each condition and subject. t t =0.8 s 2 VCs carrier VCs carrier ---- VC1 VC2 VC VC1 VC2 VC3 VC4 VC Rev-C Rev-T Carrier phrase Target tttt Rev-T R1R2AE Rev-C 2VCs or 4VCs AE R AE - R1 RmRm R nm - R2 R nm RmRm -

Experimental Results Carrier Reverberation 2VCs % Correct target identification Rev-T R1R2AE Rev-C 2VCs or 4VCs AE R AE - R1 RmRm R nm - A2 R nm RmRm - 4VCs RmRm RmRm R nm R AE ** * ○ ： Rev-T ＝ R1 ， ● ： Rev-T=R2  The effect of Rev-C is significant only with Rev-T=R2 (p<.0001): performance with matching reverberation is significantly higher than unmatching rev. with Rev-T=R2.  The effect of the carrier length is not significant.  Condition means of the PC: across 14 subjects and two repetitions  Error bars: showing 95 % confidence intervals for mean within subject (14 data)

Analysis of BNIR - reverberation Frequency [Hz] Reverberation Energy (Rev(50ms-)/Dir(0-50ms)) Frequency [Hz] Reverberation Time (T60) R1R1 R2R2 Frequency [Hz] FFT of early 100ms Relative level [dB] SNR and STI R1 R2

Summary  Calibration to room reverberation improved consonant perception in one (but not in the other) room explored in this study.  The two rooms differ in several acoustic characteristics, which might be the cause of this effect.  The calibration occurs quickly, after just a few words.

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