Objective: The goals of this research were to develop and evaluate a new version of the Listening in Spatialized Noise Test (LISN; Cameron Dillon & Newall, 2006a) by incorporating a simplified and more objective response protocol to make the test suitable for assessing the ability of children as young as 5 yr to understand speech in background noise. The LISN-Sentences test (LISN-S; Cameron & Dillon, Reference Note 1) produces a three-dimensional auditory environment under headphones and is presented by using a personal computer. A simple repetition response protocol is used to determine speech reception thresholds (SRTs) for sentences presented in competing speech under various conditions. In four LISN-S conditions, the maskers are manipulated with respect to location (0 degrees versus +/-90 degrees azimuth) and vocal quality of the speaker(s) of the stories (same as, or different than, the speaker of the target sentences). Performance is measured as two SRT measures and three "advantage" measures. These advantage measures represent the benefit in decibels gained when either talker, spatial, or both talker and spatial cues combined, are incorporated in the maskers. This use of difference scores minimizes the effects of between-listener variation in factors such as linguistic skills and general cognitive ability on LISN-S performance.
Design: An initial experiment was conducted to determine the relative intelligibility of the sentences used in the test. Up to 30 sentences were presented adaptively to 24 children ages 8 to 9 yr to estimate the SRT (eSRT). Fifty sentences each were then presented at each participant's eSRT, eSRT +2 dB, and eSRT -2 dB. Psychometric functions were fitted and the sentences were adjusted in amplitude for equal intelligibility. After adjustment, intelligibility increased across sentences by approximately 17% for each 1 dB increase in signal-to-noise ratio (SNR). A second experiment was conducted to gather normative data on the LISN-S from 82 children with normal hearing, ages 5 to 11 yr.
Results: For the 82 children in the normative data study, regression analysis showed that there was a strong trend of decreasing SRT and increasing advantage as age increased across all LISN-S performance measures. Analysis of variance revealed that significant differences in performance were most pronounced between the 5-yr-olds and the other age groups on the LISN-S measures that assess the ability to use spatial cues to understand speech in background noise, suggesting that binaural processing skills are still developing at age 5 yr. Inter-participant variation in performance on the various SRT and advantage measures was minimal for all groups, including the 5- and 6-yr-olds who exhibited standard deviations ranging from only 1.0 dB to 1.8 dB across measures. The intra-participant standard error ranged from 0.6 dB to 2.0 dB across age groups and conditions. Total time taken to administer all four LISN-S conditions was on average 12 minutes.
Conclusions: The LISN-S provides a quick, objective method of measuring a child's ability to understand speech in background noise. The small degree of inter- and intra-participant variation in the 5- and 6-yr-old children suggests that the test is capable of assessing auditory processing in this age group. However, because there appears to be a strong developmental curve in binaural processing skills in the 5-yr-olds, it is suggested that the LISN-S be used clinically with children from 6 yr of age. Cut-off scores, calculated as 2 standard deviations below the mean adjusted for age, were calculated for each performance measure for children ages 6 to 11 yr. These scores, which represent the level below which performance on the LISN-S is considered to be outside normal limits, will be used to in future studies with children with suspected central auditory processing disorder.