Liesbeth Royackers

SVD-based optimal filtering for noise reduction in dual microphone hearing aids: a real time implementation and perceptual evaluation

In this paper, the first real-time implementation and perceptual evaluation of a singular value decomposition (SVD)-based optimal filtering technique for noise reduction in a dual microphone behind-the-ear (BTE) hearing aid is presented. This evaluation was carried out for a speech weighted noise and multitalker babble, for single and multiple jammer sound source scenarios. Two basic microphone configurations in the hearing aid were used. The SVD-based optimal filtering technique was compared against an adaptive beamformer, which is known to give significant improvements in speech intelligibility in noisy environment. The optimal filtering technique works without assumptions about a speaker position, unlike the two-stage adaptive beamformer. However this strategy needs a robust voice activity detector (VAD). A method to improve the performance of the VAD was presented and evaluated physically. By connecting the VAD to the output of the noise reduction algorithms, a good discrimination between the speech-and-noise periods and the noise-only periods of the signals was obtained. The perceptual experiments demonstrated that the SVD-based optimal filtering technique could perform as well as the adaptive beamformer in a single noise source scenario, i.e., the ideal scenario for the latter technique, and could outperform the adaptive beamformer in multiple noise source scenarios.

Hearing status in children with congenital cytomegalovirus: Up-to-6-years audiological follow-up

OBJECTIVE To evaluate the audiological outcome of children with congenital cytomegalovirus infection. METHODS In a prospective study, the hearing of ninety seven congenitally cytomegalovirus-infected children, born between January 2003 and July 2009, was systematically evaluated until the age of six, applying the Flemish CMV protocol. Depending on the age of the child, the protocol provides hearing evaluation by objective-, play- or conventional audiometry. Symptomatic children with hearing loss at birth were treated with ganciclovir, if parents consented. RESULTS Seventy children had a pass on initial screening, 27 had unilateral or bilateral hearing loss. Within the normal hearing group, one asymptomatic and two symptomatic children developed late-onset hearing loss. Within the group with hearing loss, 8 children received ganciclovir, while 8 symptomatic and 11 asymptomatic children did not receive ganciclovir. As for the treated group, 37.5% of the children had stable hearing loss, one child had progressive and one child had fluctuating hearing loss. Improvement of hearing threshold occurred in 37.5% of the children. Among the untreated symptomatic children, hearing loss remained stable in 50%, while progression occurred in 37.5%. In the group of asymptomatic children with hearing loss, hearing loss was most commonly stable (72.7%). Within the group of normal hearing ears at birth (n=156), there is a significant better progression in pure tone average for ears of asymptomatic subjects in comparison to ears of symptomatic subjects (p≤0.0001). As for the group of ears with hearing loss at birth (n=38), analysis shows no evidence for a difference in pure tone average progression between the different groups (p=0.38). CONCLUSIONS Cytomegalovirus infection may cause hearing loss, in both symptomatic and asymptomatic children. Our data show a significant difference, between both groups, in the progression of pure tone average of normal hearing ears at birth, in favor of the asymptomatic children. This is not the case for ears with hearing loss at birth. However, this may be due to the small number of ears in this group. Our data show the tendency that treatment with ganciclovir increases the likelihood of improvement and reduces the likelihood of deterioration of the hearing.

Single sided deafness affects language and auditory development – a case control study

To examine auditory, linguistic and cognitive outcomes of children with single‐sided deafness (SSD). An increasing body of research suggests that children with SSD lag behind with respect to their normal hearing (NH) peers. In this study, we tap into certain developmental skills.

A real time implementation and an evaluation of an optimal filtering technique for noise reduction in dual microphone hearing aids

A real time implementation and an evaluation of a singular value decomposition (SVD) based optimal filtering technique (Doclo, S. and Moonen, M., IEEE Trans. Sig. Process., vol.50, no.9, p.2230-44, 2002) for noise reduction in a dual microphone BTE (behind-the-ear) hearing aid is presented. A method to improve the performance of a voice activity detector (VAD) is described and evaluated physically. This method is used in the real time implementation of the optimal filtering technique. A perceptual evaluation by normal hearing subjects is carried out for single and multiple jammer sound sources with speech weighted noise. The SVD-based technique can perform as well as an adaptive beamformer strategy (Maj, J.B. et al., Ear and Hearing, 2003) in a single noise scenario (i.e. the ideal scenario for the latter technique), and, can outperform the beamformer technique in a multiple noise sources scenario.