Results

1. Noise Tolerance and the Frequency Following ResponseBy:Jennifer Davis, Kendall Looney & Fuh-CherngJeng Communication Sciences and Disorders js355804@ohio.edu kl107007@ohio.edu Repeated measure two-way ANOVA (SNR by intensity) results for Frequency Error, Slope Error and Tracking Accuracy. No significant differences were seen for SNR, intensity, or in their interactions. Recall the results from Li & Jeng (2011) in which a turning point was found to be around 0 dB SNR for all intensities Results Introduction Conclusion References Hypothesis In noisy environments, it becomes harder to understand or interpret a speech signal. The phenomenon known as the “Cocktail party effect” is based on the idea that we can still understand what is said in noise (Hawley, 2004). Our ability to process changes in pitch can be measured by the FFR, a measure of neural responses coming from the brainstem that follows patterns in pitch, without any active participant participation (Jeng et al., 2010; Jeng et al., 2011). Unlike English, languages such as Mandarin Chinese are based on pitch contours and changing the pitch contour of a syllable changes the meaning of the word. Past researched completed by Li & Jeng (2011), have started to examine the effects of noise on the quality of the FFR by presenting the Mandarin syllable /yi/ and Gaussian white noise to participants’ right ears with varying intensities and SNRs to determine the effect that noise would have on each condition. Results from Li & Jeng (2011) found that the FFR was able to tolerate up to a certain amount of noise and then degraded after that point. 0 dB SNR was found to be this “turning point” where the FFR started to degrade. Hawley, M., Litovsky, R.Y., Culling, J.F. (2004). The benefit of binaural hearing in a cocktail party: Effect of location and type of interferer. AcoustSoc Am, 115(2), 833-843 Jeng, F.-C., Hu, J., Dickman, M. B., Montgomery-Reagan, K., Tong, M., Wu, G., & Lin, C.-D. (2011). Cross-linguistic comparison of frequency-following responses to voice pitch in American and Chinese neonates and adults. Ear Hear, 32(6), 699-707 Jeng, F.-C., Schnabel, E. A., Dickman, B. M., Hu, J., Li, X., Lin, C.-D., & Chung, H.-K. (2010). Early maturation of frequency-following responses to voice pitch in infants with normal hearing. Percept Mot Skills, 111(3), 765-784 Li, X. & Jeng, F.-C. (2011). Noise tolerance in human frequency-following responses to voice pitch. J AcoustSoc Am, 129(1), EL21-26 Research for this project was supported by Dr. Fuh-CherngJeng’s HTC funds and the Communication Sciences and Disorders department. We would like to thank Jiong Hu, Johnny Sabol and Grant Hollister for all of their help this year! Acknowledgments Methodology 12 Mandarin-speaking adults (2 male, 10 female) Aged 18-28 years old participated in this study Recruited from the Ohio University campus and surrounding communities All participants were determined to have normal hearing sensitivity by a hearing screening of 250-8000 Hz Mandarin Syllable /yi/ presented to the right ear and white noise to the left ear Recorded from a male, Mandarin speaker at 20,000 samples/s for a duration of 250 ms and a stimulus envelope with 10 ms rise and fall time Gaussian white noise: 6 SNR conditions: No noise, 12, 6, 0, -6 and -12 dB Three Intensities: 40, 55 and 70 dB SPL 3,000 sweeps/condition with a 45 ms silent interval between onset and offset Electrically & acoustically treated room Reclined, resting position with eyes closed Three gold-plated electrodes with all impedances < 3 kΩ High Forehead: Inverting; Right Mastoid: Non-inverting; Left Mastoid: Ground Amplified, filtered to 10-3000 Hz and digitized at rate of 20,000 samples/s using IHS Abstract In 2011, Li & Jeng studied the effects of noise on the FFR when the signal stimulus, /i/ and the Gaussian white noise were presented to the same ear. Their findings showed a turning point of around 0 dB SNR, at which the FFR began to degrade. The present study examined the effects of noise on the FFR when the same stimulus and noise were presented to opposite ears. Native Mandarin speakers (2 male, 10 female) were recruited from Ohio University and the surrounding community. There were 18 conditions in total with varying intensities of 40, 55 and 70 dB SPL and varying SNRs of No Noise, -12, -6, 0, +6 and +12 dB SNR. Results showed a slight decrease in robustness of the FFR as the SNR conditions worsened; however, the FFR remained relatively stable and indicated no clear turning point. When comparing results from Li & Jeng’s 2011 study with the present study, we suspect the noise tolerance processing to be a peripheral mechanism. Figure 1. Grand-Averaged Spectrograms Figure 1 shows grand-averaged spectrograms created using the data from 12 normal hearing Mandarin-speaking participants for all 18 conditions. As is evidenced in this figure, the FFR is relatively stable across all 18 conditions. Figure 2. Objective Indices Table 1. Two-way Analysis of Variance (ANOVA) We hypothesized that noise tolerance processing occurs centrally, meaning the FFR to voice pitch, will be able to tolerate up to a certain amount of noise and then degrade after that point. tested. This finding was in agreement with their hypothesis and indicates that the FFR is able to tolerate up to a certain amount of noise and then begins to degrade after that turning point. The results of our study showed that the FFR remained relatively stable across all 18 conditions without a clear turning point, even though there is a slight decrease in robustness of the FFR as the SNR conditions worsened. The degradation of the stimulus on the FFR due to noise in the opposite ear may be more clearly seen at conditions worse than -12 dB SNR, however due to high intensities that may cause damage to one’s hearing and conditions that may become stressful to participants; we are unable to examine such conditions. Comparing results from Li & Jeng (2011) with the present study indicates that the noise tolerance processing is primarily a peripheral mechanism. It is suspected that this processing may be peripheral due to the fact that when noise was played to a different ear than the stimulus, it did not interfere with the FFR as much as when the stimulus and noise were presented to the same ear. It is likely there is also a central component that assists in processing incoming information from each ear. Everyday listening environments are unlike laboratory settings which allow for different stimuli to be completely separated. Instead, the brain is able to process multiple pieces of incoming stimuli from the ears at once. In order for this to happen, there must be a central processing component where information from each ear comes together to form one, integrated message. Three objective indices, Frequency Error (A), Slope Error (B) and Tracking Accuracy (C), derived from grand-averaged spectrograms are plotted as a function of SNR at the three stimulus intensities (40, 55 and 70 dB SPL).