METHODOLOGY

1. Does acoustic fundamental frequency information enhance cochlear implant performance? Laura Mulhern and Dr. Helen Cullington lmm204@soton.ac.uk Colours used to show results in Figure 2 are matched to participants in Table 1. INTRODUCTION HYPOTHESES DISCUSSION • Low frequency information via a hearing aid has been shown to increase speech intelligibility in noise for CI listeners. • Some studies suggest fundamental frequency (F0)provides this advantage (Brown and Bacon, 2009; Chang et al., 2006), while others question the importance of F0 (Kong and Carlyon, 2007). • Currently only one study assesses the benefit with CI patients (Brown and Bacon, 2009); the others use CI simulations. They found a significant benefit of acoustic F0 information to CI listeners, however: • 1. they used patients who have exceptionally • good residual hearing • 2. They only provide the target acoustically, thus • increasing the signal to noise ratio (SNR) • If the addition of F0 provides significant benefit to speech recognition in noise then F0 information must provide a cue to aid speech in noise performance. • 2. If the addition of F0 provides equal benefit to the addition of the entire acoustic information with all other cues omitted, the F0 must be the salient cue that provides the benefit. Our results suggest that the acoustic low-frequency and F0 information have no significant impact on speech recognition in noise in CI listeners. • This conclusion is not in agreement with other studies that suggest that low-frequency acoustic cues aid speech recognition (Chang et al., 2006) or that acoustic F0 cues aid CI listeners (Brown and Bacon, 2009). • Possible reasons for the discrepancy: • both the target and masker were presented acoustically (therefore the SNR was not changed) • typical CI listeners were used (those who had any amount of residual hearing below 500 Hz contralateral to the CI) not good ‘EAS’ users. • Despite no statistical difference, most participants have chosen to continue wearing a hearing aid since they feel they obtain a benefit. • One participant (F0Filt7, not recorded in results) was unable to achieve an adequate SRT score for the CI alone condition yet could successfully complete the adaptive test for both the filt and F0 conditions. • Limitations • Low frequency acoustic information may have been too quiet for the subjects to obtain benefit. • Only ‘good’ CI users participated (score >75% on BKB sentences in quiet) due to the use of the adaptive test in noise. • Low statistical power (5%). RESULTS A one-way repeated measures ANOVA showed no significant effect on speech intelligibility in noise between the three listening conditions (p=.126). Figure 2: Individual SRTs for all seven participants in the three listening conditions. Figure 3: The median, minimum and maximum data values and the interquartile range of SRT scores for each listening condition. No correlations were found between filt acoustic benefit (CI SRT minus filt SRT) or F0 acoustic benefit (CI SRT minus F0 SRT) and participant age, gender, processor, length of CI experience, residual hearing or bimodal status. A one-way repeated measures ANOVA on the order of conditions was insignificant, therefore any learning effect was negligible. METHODOLOGY Aim To investigate the contribution of acoustic low-frequency and F0 information using typical CI users. Participants Seven adult participants aged 34-84 years, with a score >75% on BKB sentences in quiet and aidable residual hearing <500 Hz. Table 1: Demographic data for participants Materials Target: BKB sentences spoken by maleMasker: IEEE sentences spoken by female Acoustic target and masker filtered through MATLAB using 3rd order elliptical filters with a cut-off at 500 Hz. F0 of target and masker extracted using PRAAT speech synthesis program. Unfiltered speech presented through a loudspeaker (target constant at 60 dB (A)). Filtered speech presented contralaterally via an insert earphone, intensity level adjusted to an audible and comfortable level for each participant. CONCLUSIONS • Low-frequency acoustic sound (<500 Hz) does not benefit speech recognition in noise for the participants in this study. • F0 acoustic information does not benefit speech recognition in noise for the participants in this study. FUTURE DIRECTION The experiment should be repeated with a larger sample size, thus improving the statistical power. LITERATURE Brown, C.A. and Bacon, S.P. 2009. Achieving electric-acoustic benefit with modulated tone. Ear and Hearing. (In press). Chang, J.E., Bai, J.Y. and Zeng, F. 2006. Unintelligible low-frequency sound enhances simulated cochlear-implant speech recognition in noise. IEEE Transactions on Biomedical Engineering 53, 2598-2601. Cullington, H.E. and Zeng, F. 2009. Bimodal hearing benefit for speech recognition with competing voice in cochlear implant subject with normal hearing in contralateral ear. Ear and Hearing. (In press). Kong, Y. and Carlyon, R.P. 2007. Improved speech recognition in noise in simulated binaurally combined acoustic and electric stimulation. The Journal of the Acoustical Society of America 121, 3717-3727. Figure 1: A spectrogram of an example sentence highlighting the extracted F0. The blue line indicates the F0, that has a mean frequency of 151 Hz and inter-sentence variation from 98 – 300 Hz. Design 1-up, 1-down adaptive procedure to measure the speech reception threshold (SRT) of three listening conditions: 1. CI alone 2. CI and acoustic <500 Hz filtered speech contralaterally (filt) 3. CI and acoustic F0 filtered speech contralaterally (F0) SRT: SNR at which subjects score 50% correct ACKNOWLEDGEMENTS Patients and staff at the South of England Cochlear Implant Centre