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V The Benefit of Temporal Fine Structure in Spatial Release Listeners gained a 3.7 dB benefit to spatial release from masking From Masking for Older Hearing-Impaired Listeners Andrew King1,2 Lars Bramsløw1 Renskje K Hietkamp1 Marianna Vatti1 Atefeh Hafez1 Niels Henrik Pontoppidan1 Kathryn Hopkins2 Scan to access poster PDF. with the original, compared to tone-vocoded, temporal fine Eriksholm Research Centre Oticon A/S Snekkersten Denmark. 1 structure. The benefit was best predicted by low-frequency School of Psychological Sciences University of Manchester Manchester United Kingdom. 2 audiometric thresholds. QUESTIONS: ANSWERS: 1. Can older, hearing-impaired (HI) listeners benefit from spatially separating target and masker sentences? 1. Older, HI listeners benefited from spatial separation, although it was not as marked as for younger, normal-hearing listeners and varied between listeners. 2. How much benefit is lost when tone vocoding (TVC) removes cues of spatial separation in the temporal fine structure (TFS)? 2. TFS information contributed significantly to SRM: when it was disrupted, the listeners did not benefit so much from spatial separation of the sentences. M1 MHA Right ear Left ear Hearing Threshold (dB HL) 0 10 I/O Correction Linear Gain I/O Correction Linear Gain Original TFS TVC T T M2 M1 Separated M2 M1 45° 45° 45° 45° MHA I/O Correction Linear Gain Original TFS TVC IPD500 used 500 Hz pure tones, presented with a 0° starting phase in both ears in the reference stimulus. Onset and offset ramps were synchronous across ears. HYPOTHESES & RESULTS Discrimination Target Shifts Shift limit Listeners will perform better with the maskers spatially separated from the target than with the maskers colocated with the target: TMR50% was lower (better) by when speakers were separated (1.1 dB) than when co-located (3.3 dB); (F[1,19]=37.76,p<0.001). F0DL: Components are shifted by component number multiplied by modulation rate before filtering. FCk12 & FCk6: Components are shifted by a constant frequency before filtering, making them inharmonic. IPD500: Phase in the left ear is shifted positively. N/A. 30 The difference in listeners performance in separated and co-located conditions will be greater without TVC than with TVC: Spatial separation had a greater effect without TVC (4.0 dB) than with TVC (0.3 dB); (F[1,19]=38.58,p<0.001). 40 50 60 70 80 125 250 500 1000 2000 4000 8000 Frequency (Hz) Figure 1.The mean (±1 SD) audiometric thresholds in dB HL at the 11 tested frequencies for the 20 listeners in the study. METHODS Speech stimuli A special version of the Danish Dantale II corpus designed for spatial speech-on-speech testing was used (Behrens et al., 2007). Recorded words were spoken by three females. Sentences followed the structure: <Name> <Verb> <Number> <Adjective> <Object>. E.g. Henning købte tre flotte ringe. Three sentences are played simultaneously, masker 1 (M1), masker 2 (M2), and target (T). The name in sentence T is the Callsign, displayed to the listener via a computer screen hanging above the front loudspeaker. Maximum SPL at the centre of the listener’s head position was 70 dB for M1, M2 and T together. Procedure Listeners wore the MHAs which provided linear gain following CAMEQ specifications (Moore and Glasberg, 1998). One test block included TVC applied by the MHA before the gain whilst the other test block only applied gain (No TVC), these blocks were randomly ordered; within these blocks subblocks for Separated and Co-located spatial conditions were randomised (see Figure 2 for the test condition setup). Approximately a week before testing, the listeners completed a training program to familiarize them with the procedure and stimuli. For each test condition, a listener’s psychometric function is estimated from the number of correctly recalled words over 54 trials that spanned a TMR range of approximately 20 dB. The TMR that would give 50 % correct was taken as threshold (TMR 50%). Information Contact Andrew King University of Manchester [email protected] SNR (dB, estimated 50% correct) 90 6 4 0.2 FCk6 CL-TVC LR-TVC Figure 3. TMR50% in the four test conditions for each listener (open cirlces) and on average (filled diamonds) ± 1 SD. From left to right, conditions are colocated without TVC (CL-Lin), separated without TVC (LR-Lin), co-located with TVC (CL-TVC) and separated with TVC (LR-TVC). The average SRM was approximately 8-14 dB less than that achieved by NH listeners (Marrone et al., 2008; Neher et al., 2011). SRM was greater in the conditions without TVC than in the conditions with TVC. This suggests disruption of the original TFS limits the ability of old, HI listeners to benefit from spatial separation of talkers for understanding speech. Despite evidence that both age and hearing loss are associated with poor TFS sensitivity (Hopkins and Moore, 2011), some old, HI listeners can still benefit from the TFS in speech. However, the benefit is roughly half that achieved by young NH listeners (Andersen et al.2010). Without TVC, the variation in SRM for HI listeners (−0.9 dB to 8.4 dB), was very similar to that found by Marrone et al. (2008). This is generally greater than the variability seen in NH listeners (Behrens et al. 2008). 0.6 0.8 1.0 Performance on FCk12, FCk6 and/or IPD500 will account for variance in the benefit of TFS to SRM that is not accounted for by audiometric thresholds between .125 and 1.5 kHz (PTALF): Whilst the FCk6 test was significantly correlated with the benefit of TFS to SRM, a multiple linear regression model with a stepwise method of entering and removing predictor variables only included PTALF and excluded FCk6, F0DL and IPD500 scores and listener age. PTALF 8 6 6 4 4 2 2 30 35 40 45 4 50 Hearing Loss (dB, HL) 8 F0DL 1.0 1.2 Frequency (kHz) Binaural 1.4 16 32 Carrier Frequency Shift (Hz) 64 IPD500 Spear. R = −0.40 6 4 4 2 2 0 r = −0.17 8 6 0 2 4 6 8 10 12 Modulation Rate Shift (Hz) 14 50 100 200 Phase shift (μs) 400 800 Figure 6. Scatterplots of the difference in SRM with TVC and without TVC (TFS benefit to SRM) and (clockwise from top left) low frequency audiometric thresholds (PTALF), harmonic and frequency shifted complex discrimination (FCk6), IPD discrimination (IPD500) and fundamental frequency difference limens (F0DL). Correlation coefficients are given in each panel. 1.6 DISCUSSION + 1.0 r = −0.64 0 0 8 FCk12 – FCk6 8 F0DL 0.8 DISCUSSION 0.4 r = −0.76 0 LR-Lin 1.0 Figure 6 shows the scatterplots illustrating these correlations. None of the listeners performed the FCk12 test better than by chance. 180° −2 CL-Lin 0.8 Thresholds on some or all the psychoacoustic tests will correlate negatively with benefit of TFS to SRM: TFS benefit to SRM was correlated with FCk6 scores (r=−0.64, p<0.01) and with PTALF (r=−0.76,p<0.001), but not with IPD500 scores (r=−0.17, p>0.05) or F0DL scores (Spearman R= −0.40, p>0.05). Procedure Monaural Individual scores Mean (±1 SD) 0.6 The PTALF model provided an adjusted R 2 of 0.55. 2.0 3.0 Time (ms) 4.0 1.0 2.0 3.0 Time (ms) 4.0 Figure 4. A schematic of the stimuli in the three monaural pschyoacoustic tasks (top three panels) and the IPD discrimination task (bottom two panels). Light turquoise indicates the target stimuli, whilst the dark turquoise indicates the reference stimuli. Peissig and Kollmeier (1997) found audiometric threshold to be a poor predictor of SRM. However, Neher et al (2011) found a moderate correlation between low frequency audiometric thresholds and SRM. The current results suggest that PTALF is a good predictor of the benefit of TFS in SRM. Neher et al. also found a relationship between IPD discrimination and SRM. However, the current study did not find IPD500 to be a good predictor of the TFS benefit to SRM, despite the IPD500 task relying on binaural TFS cues. REFERENCES: Andersen, M. R., Kristensen, M. S., Neher, T., and Lunner, T. (2010). Effect of Binaural Tone Vocoding on Recognising Target Speech Presented Against Spatially Separated Speech Maskers. Poster at IHCON. Behrens, T., Neher, T., and Johannesson, R.B. (2007). ERH-42-08-05 Evaluation of a Danish speech corpus for assessment of spatial unmasking. Poster at ISAAR. Behrens T., Neher T. and Johannesson R.B. (2008). Evaluation of speech corpus for assessment of spatial release from masking. In: T. Dau et al (eds.) Auditory Signal Processing in Hearing-Impaired Listeners. Copenhagen, Denmark: Centertryk A/S, pp. 449–457. eriksholm.com Duquesnoy, A. J. (1983). Effect of a single interfering noise or speech source on the binaural sentence intelligibility of aged persons, J. Acoust. Soc. Am. 74, 739-743. Gatehouse, R. W., and Noble, W. (2004). The speech, spatial and qualities of hearing scale (SSQ), Int. J. Audiol. 43, 85-99. Eriksholm Research Centre Rørtangvej 20 DK - 3070 Snekkersten Phone +45 4829 8900 0.0 F0DL F0DL, FCk12 and FCk6 were presented monaurally to the left ear, whilst IPD500 was presented binaurally. See Figure 4 for diagrams of the stimuli. 2 −6 0.4 Time (s) 25 −4 0.2 HYPOTHESES & RESULTS Modulation rate / 2. A geometric adaptive procedure tracked 71% correct (Levitt, 1971). Up to three tracks were performed for each test by each listener and the geometric mean of these results was used as that listener’s threshold.If the listener could not discriminate the maximally-shifted stimulus from the reference stimulus, 40 trials were presented with the maximum shift, then the adaptive track was run again if the listener scored better than 65% correct. 8 0.0 Time (s) METHODS Figure 2. The four test conditions for the SRM experiment. Each listener performed all four conditions. – Figure 5. A schematic of the two-interval, two-alternative forced choice discrimination task used for F0DL, FCk12, FCk6 and IPD500 tests. Both intervals included noise. Light turquoise indicates the target stimulus, whilst the dark turquoise indicates the reference stimulus. F0DL and FCk12 used harmonic complexes with a modulation rate of 100 Hz. FCk6 used a modulation rate of 200 Hz. Stimuli were bandpass filtered around a centre frequency of 1.2 kHz, passing five components with a 30 dB/octave rolloff. Therefore F0DL and FCk12 passed the 10th to the 14th harmonic components and FCk6 passed the 4th to the 8th harmonic components. MHA I/O Correction Linear Gain + – Stimuli Listeners will perform better without TVC than with TVC: TMR50% was higher with TVC (3.6 dB) than without (0.8 dB); (F[1,19]=87.00,p<0.001). 20 Amplitude In addition to the age and hearing loss data already collected, we measured listeners’ fundamental frequency difference limens (F0DL), discrimination thresholds of IPDs (IPD500), and discrimination thresholds of harmonic and frequency-shifted bandpass complexes centred around the twelfth harmonic (FCk12) and around the sixth harmonic (FCk6). MHA 2 interval, 2 alternative forced-choice + Threshold Equalizing Noise – + TFS benefit to SRM (dB) −10 + TFS benefit to SRM (dB) Listeners ranged from 64 to 86 years old and had bilateral, gently sloping sensorineural hearing loss (see Figure 1). Asymmetry across ears was < 15 dB at any audiometric frequency tested (125 Hz to 8 kHz). All listeners spoke Danish as their first language. PREDICTING TFS BENEFIT TO SRM M2 Component Magnitude LISTENERS T Neher et al. (2011) found IPD discrimination and low frequency audiometric thresholds predicted SRM performance in listeners with hearing loss. To explain the wide variation in TFS benefit to SRM for HI listeners, a battery of tests including TFS sensitivity were conducted with the same listeners. Andersen et al. (2010) showed normal-hearing (NH) listeners achieve greater SRM when the speech signals contain their original TFS than when the speech has TVC applied to it. Andersen et al. split the speech signal into 32 ERBN frequency bands (Glasberg and Moore, 1990), took the envelope from each band and multiplied it by a pure tone at the band centre frequency. The current study extends the study of Andersen et al. (2010) by using a master hearing aid system (MHA) to apply TVC and amplify the sounds presented from loudspeakers in an anechoic room, rather than processing the sounds with generic head related transfer functions before presenting them over headphones. Using the MHA is more ecologically valid than headphone presentation for hearing aid users as it processes the sounds at the listener’s ear, allowing the listener’s own head and torso to affect the sounds, including head movements. M1 Amplitude Old, HI people, struggle to understand a target sound when they are in a noisy environment (Duquesnoy, 1983; Gatehouse and Noble, 2004). This may be because hearing loss is associated with poorer SRM (Marrone et al., 2008; Neher et al., 2009). TVC M2 Co-located SRM is the ability to hear target sounds over maskers more easily when the sounds come from different directions than when all sounds come from the same direction. T Amplitude No TVC BACKGROUND 3. Benefit from TFS to SRM was not correlated with interaural phase difference (IPD) discrimination of pure tones in noise. Rather, the best predictor to the TFS benefit to SRM was audiometric hearing loss below 1.5 kHz, over which TFS measures accounted for no extra variability. Amplitude 3. Can discrimination tasks designed to measure TFS processing predict individual differences in how much TVC affects spatial release from masking (SRM)? Glasberg, B. R.; Moore, B. C. J. (1990). Derivation of auditory filter shapes from notched-noise data, Hear. Res. 47, 103–138. Hopkins, K., and Moore, B. C. J. (2011). The effects of age and cochlear hearing loss on temporal fine structure sensitivity, frequency selectivity, and speech reception in noise, J. Acoust. Soc. Am. 130, 334-349. Levitt, H. C. C. H. (1971). Transformed up‐down methods in psychoacoustics. J. Acoust Soc. Am., 49, 467–477. Marrone, N., Mason, C. R., and Gerald Kidd, J. (2008). The effects of hearing loss and age on the benefit of spatial separation between multiple talkers in reverberant rooms,J. Acoust. Soc. Am. 124, 3064-3075. Moore, B.C.J. and Glasberg, B.R. (1998). Use of a loudness model for hearing-aid fitting. I. Linear hearing aids. Brit. J. Audiol. 32(5), 317-325. Neher, T., Behrens, T., Carlile, S., Jin, C., Kragelund, L., Petersen, A. S., and Schaik, A. (2009). Benefit from spatial separation of multiple talkers in bilateral hearing-aid users: Effects of hearing loss, age, and cognition, Int. J. Audiol. 48, 758-774. Peissig, J., and Kollmeier, J. (1997). Directivity of binaural noise reduction in spatial multiple noise-source arrangements for normal and impaired listeners, J. Acoust. Soc. Am. 101, 1660-1670. IN COOPERATION WITH