Towards quantifying cochlear implant localisation performance in complex 
acoustic environments

Stefan Kerber (1), Paula Greenham (2) and Bernhard U. Seeber (1)

(1)
MRC Institute of Hearing Research
University Park, Science Road
Nottingham
NG7 2RD

(2)
Cochlear Inc.


Background

Patients with bilateral cochlear implants may be able to localise sounds in 
quiet, but this becomes difficult in situations with background noise and 
reverberation present, i.e. in so-called complex acoustic environments. Being 
unable to attend correctly and quickly enough to a speaker makes it impossible 
to lip-read and thus more difficult and mentally demanding to follow a 
conversation – a common complaint amongst school children with cochlear 
implants. However, systematic investigations of localisation abilities in 
complex acoustic environments are rare. Therefore, a test battery to quantify 
localisation ability with cochlear implants is proposed.

Methods

Participants sit in an anechoic chamber and use a trackball to position a 
light-pointer to the perceived position of different sounds they hear. Sounds 
are presented in the horizontal plane from the frontal hemifield (i) in 
anechoic conditions, (ii) in simultaneous background noise, (iii) with 
simulated reverberation and (iv) with a single reflection added. The test 
battery is completed by a speech test, a cognitive test and the SSQ 
questionnaire.

Results

Results show that the performance of cochlear implant patients differs 
considerably from that of normal hearing participants and patients wearing 
bilateral hearing aids. Localisation performance for cochlear implant users 
starts to degrade at lower levels of background noise and reflections - in 
accordance with informal patient reports.

Conclusion

The proposed test battery is suitable to quantify the localisation problems 
reported informally by patients. For the future we plan to use data obtained 
with the localisation test battery to find predictors for performance in 
complex acoustic environments.