Effects of Broadband Noise on Frequency-Following Response to Voice Pitch

1. Effects of Broadband Noise on Frequency-Following Response to Voice Pitch Ximing Li

2. Specific aim • the study aims to examine the effects of broadband noise on frequency-following response (FFR) , in aspects of signal-to-noise ratio (SNR) and signal intensity level.

3. Background • FFR is scalp recorded response; reflecting the phase-locking activity from ensemble neurons in brainstem area; • Can be evoked by toneburst, two tones, tonal sweeps and speech (Hoormann, 1992; Krishnan et al., 2002, 2004; Galbraith et al., 1995; Cunningham et al., 2001; Russo et al., 2004). • FFR preserved pitch-related information; assess pitch perception (Krishnan et al., 2004).

4. Effects of noise on scalp-recorded response • on auditory brainstem response (ABR) (Burkard and Hecox, 1983) Both noise level and intensity level showed effects; • on cortical P1-N1-P2 complex (Billings, 2009) Response was mainly affected by SNR;

5. Mechanism of pitch perception in noise • Another benefit of studying this topic was to learn the effects of broadband noise on pitch perception; • Previous studies on speech evoked ABR (Cunningham et al., 2001; Russo et al., 2004): • response degraded in noisy condition (SNR+5 dB): rms amplitdue decreased; latency delayed; • FFR part sustained;

6. Hypothesis • FFR originates from brainstem area (Snyder and Schreiner, 1984; Hooremann et al., 1992) • Broadband noise would have the effects on FFR similar as on ABR. • It was hypothesized that SNR and intensity level should have a combined effect on FFR.

7. Method • Subjects: • 9 native Chinese speakers (5 males, 4 females) aged between 20 to 30 years old; • All subjects were with normal hearing.

8. Method • Stimuli: • Mandarin i2 tone plus background noise at various conditions: intensity level conditions: 70, 55, 40 dB SPL; SNR level conditions: Quiet, +12 dB, +6 dB, 0 dB, -6 dB and -12 dB. • Conditions were presented randomly; • One condition 2000 sweeps recorded.

9. Method • Recording: • Bipolar montage: lower forehead (Fz) as positive, right mastoid bone (M2) as reference, left mastoid bone (M1) as ground;

10. Method • Data Analysis: • Preprocessing: band pass filtered (100 to 1500 Hz), segmented, baseline corrected, criterion rejected(±25 μV) and averaged; • For each condition, spectrograms were averaged across subjects; • Three parameters quantified for evaluation: frequency error, slope error and pitch tracking accuracy.

11. Method Response contour

12. Method response stimuli

13. Method Correlation Pitch tracking accuracy ∑ ∆ frequency Frequency error Time bin ∆ slope Slope error

14. Results – frequency error

15. Results – frequency error

16. Results – frequency error

17. Results – frequency error

18. Results – slope error

19. Results – pitch tracking accuracy

20. Results • The 0 dB SNR point is a key point; • When SNR is larger or equal to 0 dB, the intensity level dose not show large effect on response; • When SNR is less than 0 dB, the response becomes worse as SNR decreases and is largely affected by intensity level.

21. Thanks a lot!!