Fundamental frequency is critical to speech perception in noise in combined acoustic and electric hearing

Abstract

Cochlear implant (CI) users have been shown to benefit from residual low-frequency hearing, specifically in pitch related tasks. It remains unclear whether this benefit is dependent on fundamental frequency (F0) or other acoustic cues. Three experiments were conducted to determine the role of F0, as well as its frequency modulated (FM) and amplitude modulated (AM) components, in speech recognition with a competing voice. In simulated CI listeners, the signal-to-noise ratio was varied to estimate the 50% correct response. Simulation results showed that the F0 cue contributes to a significant proportion of the benefit seen with combined acoustic and electric hearing, and additionally that this benefit is due to the FM rather than the AM component. In actual CI users, sentence recognition scores were collected with either the full F0 cue containing both the FM and AM components or the 500-Hz low-pass speech cue containing the F0 and additional harmonics. The F0 cue provided a benefit similar to the low-pass cue for speech in noise, but not in quiet. Poorer CI users benefited more from the F0 cue than better users. These findings suggest that F0 is critical to improving speech perception in noise in combined acoustic and electric hearing.

Robustness against distortion of fundamental frequency cues in simulated electro-acoustic hearing

“…Carroll et al (2011) found a similar pattern (2.3 dB and 4 dB respectively), although both comparisons were significant. The amplitude of the pure tone indicates voicing but our results show that the presence of only the voicing cue has no significant benefit over the CI simulation -this is in line with the results of Carroll et al (2011) and . Consequently, our study confirms that the presence of the target's fundamental frequency, and, in particular, its variation in frequency is an important cue for improving speech recognition in noise.…”

“…Some authors use the abbreviation SRT but, as explained by Carroll et al (2011), this would not be correct in the present context because the SRT is initially defined as the absolute level in quiet, and not as a relative level in noise. The advantage of the measure chosen is that there is no need to present several lists with a different SNR for each listing condition, meaning that more conditions can be evaluated, and the SNR required for a 50% correct performance can be assessed without ceiling effects within the length of one list of the BKB sentences with an adaptive procedure.…”

“…The advantage of the measure chosen is that there is no need to present several lists with a different SNR for each listing condition, meaning that more conditions can be evaluated, and the SNR required for a 50% correct performance can be assessed without ceiling effects within the length of one list of the BKB sentences with an adaptive procedure. The adaptive procedure used has been inspired by the procedures of Turner et al (2004) and Carroll et al (2011); it starts at an 'easy' SNR with a step size of 5 dB and after one reversal the step size is decreased to 2 dB, and after four reversals the step size is decreased further to 1 dB. The first sentence of the first list was presented at a fixed SNR of 5 dB and the subsequent lists started 5 dB above the final SNR of the previous list.…”

“…Few other studies have used this performance measure so it is difficult to compare values; Chang et al (2006) found a score of 0 dB for the EAS setting (down from 10 dB for the 4-channel CI simulation), and Carroll et al (2011) report a score of about 5 dB for the EAS setting with a cut-off frequency of 500 Hz (down from 11.6 dB for the 6-channel CI simulation). Results of Kong and Carlyon (2007) reflect SNRs which are similar to the values measured by Carroll et al (2011). Although the score for the EAS setting in our experiment is close to scores reported by the other authors, the benefit observed is smaller.…”

The role of continuous low-frequency harmonicity cues for interrupted speech perception in bimodal hearing

“…It is now widely accepted that electric-acoustic stimulation (EAS) in the form of bimodal hearing [cochlear implant (CI) supplemented by low-frequency acoustic hearing in the contralateral ear] or hybrid hearing (CI supplemented by low-frequency acoustic hearing preserved postoperatively in the same ear) has the potential to enhance speech understanding relative to a CI alone (see reviews by Gifford, 2008, 2010). This is especially true when the target speech signal occurs in the presence of competing maskers or background noise (e.g., real EAS users: Kong et al, 2005;Zhang et al, 2010;Carroll et al, 2011;Visram et al, 2012a,b;Neuman and Svirsky, 2013; simulated EAS listeners: Qin and Oxenham, 2006;Li and Loizou, 2008;Tillery et al, 2012).…”