Sound Localization and Binaural Hearing in Children with a Hearing Aid and a Cochlear Implant

Abstract

The aims of the study were to investigate whether sound localization acuity improved when children with 1 cochlear implant use a hearing aid in the contralateral ear (bimodal fitting), and whether this enabled them to benefit from a binaural masking level difference. Four different noise bursts were used as stimuli for a minimal audible angle localization test. On average, localization acuity remained poor with the cochlear implant alone, but also with bimodal fitting. A significant benefit of bimodal fitting was only shown when the most complicated stimulus with roved amplitude and spectrum was presented (minimal audible angle of 151° with bimodal fitting vs. 175° with cochlear implant alone). No significant binaural masking level difference was found between the cochlear implant alone and the bimodal condition.

Development of Auditory Localization Accuracy and Auditory Spatial Discrimination in Children and Adolescents

“…To date, there are no MAA studies examining a large number of healthy children at different ages and within a wide range of acoustic space. The available small database already shows a trend for the continuous development of spatial hearing; in an unpublished Dutch study [cited in Beijen et al, 2010], 14 participants with normal hearing (6-19 years) showed an average MAA threshold of 10° for 500-ms broadband-noise pulses (0.3-7 kHz) presented either from the left or from the right side while abstaining from the use of reference signals at 0°. Related to the presently used measurement method (3-AFC), this corresponds to an MAA threshold of 5°.…”

“…To date, published data mostly refer to the spatial hearing abilities of adults [Makous and Middlebrooks, 1990;Perrott and Saberi, 1990;Middlebrooks and Green, 1991;Blauert, 1997;Sabin et al, 2005]. Respective data for children are rather sparse, and were mostly collected as mere comparative data for studies on children with hearing impairments or cochlear implants [Bess et al, 1986;Beijen et al, 2010]. Infants have also been studied, and in these studies -because of the limited ability of infants to cooperate in behavioral studies requiring voluntary decisionsstimulus-induced head/eye movements were used to indicate the detection of a shift in sound source location.…”

“…Firstly, the terms 'identification of source location' and 'MAA' are being used alternately in some of the studies employing absolute localization tasks (such as left-right discrimination without a reference signal) [e.g. Morrongiello and Rocca, 1990;Beijen et al, 2010;Godar and Litovsky, 2010]. Today, researchers agree on the fact that absolute localization (source identification) and spatial discrimination (MAA) are not only two different auditory tasks, but are also (at least partially) processed at different stages of the ascending auditory pathway [Zatorre et al, 2002;Spierer et al, 2009].…”

“…To date, clinical diagnostic tools mainly use speech material, making it difficult to differentiate between genuine auditory performance and speech-related impairments of the tested patients. In recent years, it has also been suggested to include an evaluation of spatial hearing abilities in the assessment of cochlear implant users [Litvosky et al, 2006;Beijen et al, 2010] and of persons with conventional hearing aids.…”

A comparison of the speech recognition and pitch ranking abilities of children using a unilateral cochlear implant, bimodal stimulation or bilateral hearing aids

“…'Binaural squelch' refers to a range of central auditory processing mechanisms which improve the effective SNR by analysing differences in the phase and level of the signal arriving at each ear. Neither adult, nor child users of BMS are able to fully utilise binaural squelch mechanisms as current speech processing strategies are unable to reliably code phase information required for the perception of interaural timing and phase differences [7,23]. The 'head shadow effect' is caused by interactions between the acoustic signal and the head which result in between-ear differences in the SNR at each ear.…”