4aPPa32. How Susceptibility To Noise Varies Across Speech Frequencies Sarah E. Yoho1, Eric W. Healy, Frédéric Apoux2 Department of Speech and Hearing Science The Ohio State University Currently at Department of Communicative Disorders and Deaf Education, Utah State University Currently at Department of Otolaryngology - Head & Neck Surgery, The Ohio State University Purpose: To determine the particular susceptibility to noise of individual bands of speech 1. Intelligibility Functions 4. Importance / Susceptibility General Method: IEEE sentences (IEEE, 1969) 21 ‘critical bands’ as specified in ANSI SII (ANSI, 1997) 10 talkers (5 male), general American dialect Subjects all young adults, normal hearing, native speakers of English Baseline Scores: Band absent and band present in quiet scores used as baseline intelligibility (from Yoho et al., in review) 20 subjects randomly assigned into three groups (Bands 1-7; 8-14; 15-21) Target band presented with four other bands randomly assigned from trial-to-trial (band present), or four randomly-assigned other bands presented without target (band absent) 20 sentences/band condition; total of 140 sentences/subject Broadband speech set to 70 dBA Noise Susceptibility: 40 subjects divided into two groups (odd bands; even bands) Band 1 excluded due to very low importance value Target band presented with 4 other bands, randomly assigned from trial-to-trial Gaussian noise added to target band at six SNRs: -12, -8, -4, 0, 4, 8 dB Noise had 10-ms raised cosine rise/fall, started at least 300 ms prior to speech 10 sentences/ condition, 60 total conditions: (10 Target Bands x 6 SNRs) Noise Susceptibility Definition: Amount of noise (SNR) required to reduce performance for that target band halfway from band present in quiet to band absent in quiet Fig 6. Relationship between noise susceptibility (in dB SNR) and band importance for the twenty bands tested here (r = -0.238, p = .312). Fig 2. Sentence intelligibility in percent correct as a function of target band signal-to-noise ratio for the ten even-numbered critical bands. The dashed top and bottom lines in each panel are average ‘band-present’ and ‘band absent’ sentence intelligibility, respectively, for that target band. The dotted line in each panel is the midway point between band present and band absent for that target band. Fig 3. Same as for Fig 2., but for the ten odd-numbered critical bands tested. Results and Conclusions: Results suggest that susceptibility to noise is not equal across the speech spectrum There is large variability in noise susceptibility across the spectrum, with the lowest band being very susceptible, a region of low susceptibility in low frequencies, and no consistent pattern in high frequencies These findings are despite the use of multiple talkers- therefore they do not simply reflect any particular aspect of an individual voice There is no systematic relationship between noise susceptibility and band importance Some bands of high importance (bands with center frequencies of 1370 and 1850 Hz) displayed high susceptibility to noise Possible implications for evaluating band importance in the presence of background noise 3. Noise Susceptibility Values (SNR) 2. Additional Functions Fig 4. Same as for Figs. 2 and 3, but data from a new group of five subjects for bands 2 and 20. The dashed ‘band-present’ and ‘band-absent’ scores were obtained from these same five subjects. Fig 5. Noise susceptibility as equivalent signal-to-noise ratios for the target bands indicated. Values for bands having center frequencies of 250 and 7000 Hz are from the group of five subjects shown in Fig 4. Work supported in part by NIDCD grants R01 DC008594 and R01 DC 015521 to EWH American National Standard Inst. (1997). ANSI S3.5 (R2007). American National Standard Methods for the Calculation of the Speech Intelligibility Index (American National Standards Inst., New York). Apoux, F., and Healy, E. W. (2012). “Use of a compound approach to derive auditory-filter-wide frequency-importance functions for vowels and consonants,” J. Acoust. Soc. Am. 132, 1078-1087. Healy, E. W., Yoho, S. E., & Apoux, F. (2013). “Band importance for sentences and words reexamined,” J. Acoust. Soc. Am., 133, 463-473. IEEE (1969). “IEEE recommended practice for speech quality measurements,” IEEE Trans. Audio Electroacoust. 17, 225–246. Fig 1. From Yoho et al. (in review). Band importance functions for IEEE sentences by a single male talker and by 5 male and 5 female talkers. The multi-talker function (open symbols) was used for comparison here.