PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Speech enrichment: Listening effort and intelligibility
Anna EXENBERGER1; Paul IVERSON2
1,2

University College London, UKABSTRACT
In this study, we investigated differences between a hearing impaired (HI) and a normal hearing (NH) groupon subjective, behavioural and neurophysiological measures of speech processing and listening effort. We
fitted both groups with a hearing aid (HI for hearing loss compensation and NH with minimal amplification
for comparison), and asked them to perform a speech-in-noise task. The target speech was presented in multitalker babble noise in two SNRs (+5dB and 0dB). The hearing aid had three different settings: hearing loss
compensation only, noise cancelling and beam forming. EEG (64 channels) was recorded during theexperiment in order to analyse cortical entrainment as well was intersubject correlation. Results revealed amarked difference between cortical entrainment and other measures; whereas the subjective listening effort
measure, behavioural performance (intelligibility) and intersubject correlation (as a measure of auditory
attention) showed relatively small differences between the NH and the HI group, we found substantiallylarger cortical entrainment for the HI group, specifically in higher SNRs (+5dB). We suggest that these results
might indicate that processing is altered for hearing impaired people specifically in the auditory stage.
Keywords: Hearing impairment, listening effort, EEG

1. INTRODUCTION
Compared to normal hearing people, hearing impaired people suffer from increased difficulties tounderstand speech in noisy conditions. Neurophysiological measures of online speech processing canbe used to investigate this increased difficulty. Among those, there are two specifically that have been
associated with auditory attention: neural entrainment and intersubject correlation. Neural (cortical)
entrainment originates from neural oscillations in the cortex, which become phase-locked to lowfrequency temporal modulations of speech (1, 2). Previous research has shown that selective attention
can enhance cortical entrainment (3, 4, 5). Intersubject correlation (ISC), as a measure of similarityof the neural response between subjects, has been found to be significantly enhanced when listenersactively attend to a stimulus (6).
Based on previous findings and in conjunction with subjective and behavioral data, this study
investigated differences in cortical entrainment and ISC between a normal hearing and a hearing
impaired group. Additionally, the effect of algorithms commonly implemented in hearing aids (noisereduction algorithms, directional microphones) on our measures was assessed.

2. RESULTS
2.1 Cortical entrainment
Coherence in low-frequency regions (2-8Hz) to the target speaker was found to be significantly
increased in the hearing impaired group, compared to the normal hearing group. Statistical analysis
revealed a significant effect of condition (χ2 (5) = 56.489, p < 0.0001), group (χ 2 (1) = 6.7371, p <0.001) as well as the interaction between group and condition (χ 2 (5) = 34.409, p < 0.0001).

125700a.exenberger@ucl.ac.uk
p.iverson@ucl.ac.uk

Figure 1 – Cortical entrainment for the hearing impaired and normal hearing groups
2.2 Intersubject correlation
For both groups, intersubject correlation (ISC) was higher for the easier noise conditions (+5dBSNR) than for the hard conditions (0dB SNR). Additionally, the normal hearing group showed a clear
trend of higher ISC for conditions with enhancement compared to those without. For the hearing
impaired group, this trend was less consistent. Statistical analysis (model comparison) revealed asignificant effect of condition for both the normal hearing and the hearing impaired group (NH: χ 2 (5)= 59.554, p < 0.0001, HI: χ2 (5) = 31.14, p < 0.0001). We found no significant difference in ISC
between the two groups (χ 2 (1) = 0.0172, p = 0.8956).

Figure 2 – Intersubject correlation for both groups

3. CONCLUSIONS
While cortical entrainment was significantly different between the hearing impaired and the normal
hearing group, no such effect was found for ISC. These findings indicate that both groups were paying

5701

attention at similar levels, but that processing specifically in the auditory stage was altered i n thehearing impaired group.

ACKNOWLEDGEMENTS
ENRICH has received funding from the EU’s H2020 research and innovation programme underthe MSCA GA 675324.

REFERENCES
1. Ahissar E, Nagarajan S, Ahissar M, Protopapas A, Mahncke H, Merzenich MM. Speech comprehension
is correlated with tempral response pattern recorded from auditory cortex. Proc National Academy ofSciences; 2001; 98(23); p. 13367-13372.
2. Luo H, Poeppel D. Phase patterns of neuronal responses reliably discriminate speech in human auditory
cortex. Neuron 2007;54(6):1001-1010.
3. Ding N, Simon JZ. Emergence of neural encoding of auditory objects while listening to competing
speakers. Proc National Academy of Sciences; 2012; 109(29); p. 11854-11859.
4. Kerlin JR, Shahin AJ, Miller LM. Attentional gain control of ongoing cortical speech representations in a'cocktail party'. J Neuroscience 2010;30(2):620-628.
5. Zion Golumbic EM, Ding N, Bickel S, Lakatos P, Schevon CA, McKhann GM, Schroeder CE.
Mechanisms underlying selective neuronal tracking of attended speech at a 'cocktail party'. Neuron
2013;77:980-991.
6. Ki JJ, Kelly SP, Parra LC. Attention strongly modulates reliability of neural response to naturalistic
narrative stimuli. J Neuroscience 2016:36(10):3029-3101.

5702