Loudness Perception in Children Using Hearing Aids and Children Using Cochlear Implants

Abstract

The study compared two loudness perception measures (loudness growth identification & intensity discrimination) in children using a single cochlear implant (n = 25), children using binaural hearing aids (n = 20), and typically developing children (n = 31). In the children using hearing aids, the effect of compression parameters on loudness perception was also evaluated in three different conditions (own prescribed hearing aids, linear hearing aids, & non-linear hearing aids). While the participants’ own hearing aids had lesser compression compared to the non-linear hearing aids, the linear hearing aids had no compression. The children aged 6 to 15 years, were evaluated using three warble-tones (500 Hz, 1000 Hz, & 4000 Hz) and three vowels (/u/, /a/, & /i/). Loudness growth was measured using a ‘Loudness growth chart’ having six loudness levels (very soft, soft, comfortable, loud, too loud, & very loud, & paining) and intensity discrimination was assessed using a Psycon software. Only 48% of the children using cochlear implants and 65% of children using hearing aids could give consistent responses in the loudness growth identification test, while all typically developing children could do so. Further, on the loudness growth test, among the hearing aid users no significant difference occurred between the three hearing aid conditions for most stimuli. Across the three participant groups, significant differences were obtained mainly for the soft loudness levels for most stimuli. Both the clinical groups required more intensity to perceive the softer loudness levels compared to the normal hearing children. However, the children using cochlear implants did not differ significantly from the children using hearing aids for most loudness levels and stimuli. The intensity discrimination thresholds across the three hearing aid conditions were significantly better when the children used the linear hearing aids than when they wore their own prescribed hearing aids only for a few stimuli (500 Hz & 4000 Hz). On the other hand, between linear and non-linear hearing aids, the discrimination thresholds were significantly different for most stimuli (500 Hz, 1000 Hz, 4000 Hz, & /i/). Further, across the three participant groups, the typically developing children had significantly better discrimination thresholds than both the clinical groups for the majority of stimuli. However, no such difference was obtained between children using cochlear implants and children using hearing aids for most of the stimuli. Thus, from the findings of the study it was observed that the warble-tones tended to differentiate the three participant groups better than did the vowels. This was observed for both loudness perception measures that were studied. Further, it was noted that loudness growth identification and loudness discrimination thresholds varied across the three participant groups as well as across the three hearing aid conditions. This was seen only for a few stimuli. Hence, it can be inferred that the devices worn by the two clinical groups did affect loudness growth perception at low levels, but did not do so for moderate to loud signals. Intensity discrimination was also adversely affected in the clinical groups wearing listening devices when compared to typically developing children. Based on the findings of the three hearing aid conditions, it is recommended to use lesser compression in listening devices to enable children with hearing impairment to perceive loudness cues akin to typically developing children.