Past Research Projects

The Listening in Spatialized Noise - Sentences test (LISN-S, Cameron & Dillon, 2009a) is an adaptive speech-in-noise test that creates a three-dimensional auditory environment under headphones.   The LiSN-S was specifically developed to assess the ability of children with suspected central auditory processing disorder (CAPD) to understand speech when there is background noise present.  CAPD refers to a number of separate disorders with various loci of origin throughout the auditory system, which result in distortion or deletion of auditory information. 

Our research has shown that a large proportion of children with suspected CAPD have what is termed a "spatial processing disorder" or SPD (Cameron & Dillon, in press). SPD is a condition whereby individuals are deficient in their ability to use binaural cues (specifically the interaural time and intensity differences between competing auditory signals) to selectively attend to sounds arriving from one direction while simultaneously suppressing sounds arriving from another. As a result, children and adults with SPD experience greater-than-normal difficulty listening in noisy environments, such as in the classroom (Cameron & Dillon, 2008a). As such, children and adults with SPD require a more favourable signal-to-noise ratio that their normally-hearing peers in order to be able to process speech in noisy environments.

The LiSN-S utilises a simple repetition-response protocol to assess a listener's speech reception threshold (SRT) for target sentences presented in competing speech maskers (children's stories). Using HRTFs, the targets are perceived as coming from directly in front of the listener (0^o azimuth) whereas the maskers, relative to the targets, vary according to their perceived spatial location (0^o vs. + and -90^o azimuth), the vocal identity of the speaker/s of the stories (same as, or different to, the speaker of the target sentences), or both.

Performance on the LISN-S is evaluated, therefore, by comparing listeners' performances across four listening conditions, generating two SRT measures and three "advantage" measures. The advantage measures represent the benefit in dB gained when either talker, spatial, or both talker and spatial cues are incorporated in the maskers, compared to a baseline condition where no cues are present in the maskers. The use of relative measures of performance (i.e., difference scores) serve to minimize the influence of higher order language, learning and communication skills on test performance. For example, as such skills affect both the SRT when the distracters are presented at 0^o, and the SRT when they are spatially separated at - +90^o, these skills will have minimal effect on the difference between the SRTs in these two conditions. Thus, the differences that inevitably exist between individuals in such functions can be accounted for, allowing for clearer evaluation of their abilities to use spatial and voice cues to aid speech understanding.

A study was conducted with 24 children aged 8 to 9 years to determine the relative intelligibility of the sentences (Cameron & Dillon, 2007a). Psychometric functions were fitted, and the sentences adjusted for equal intelligibility. Intelligibility across sentences increases by approximately 17% for each 1dB increase in SNR.

Normative data has been collected for the Australian-accented version of the LiSN-S of the from 202 normally-hearing children and adults aged 6 to 60 years There was a trend of decreasing SRT, and increasing advantage, as age increased, across all measures. Inter- and intra-participant variation was minimal across age groups and conditions. Cut-off scores, calculated as two standard deviations below the mean adjusted for age, were calculated for each performance measure. These scores represent the level below which performance on the LISN-S is considered to be outside normal limits (Cameron & Dillon, 2007a; Cameron, Dillon & Glyde, in press).

Test-retest reliability data on the Australian-accented version of the LiSN-S was collected from 95 children (Cameron & Dillon, 2007b; Cameron, Dillon & Glyde, in press). Mean changes in performance on re-test on the LISN-S performance measures were minimal, ranging from 0.1 dB to 1.2 dB. Critical differences for test score improvements ranged from 3.3 dB to 4.7 dB, making this test suitable for detecting improvements in an individual child with CAPD following auditory compensation (such as an FM system) or remediation with the LiSN & Learn auditory training software (Cameron & Dillon, 2008b; Cameron & Dillon, 2010; Cameron & Dillon, in press).

A study was conducted to assess a group of nine children who presented with difficulties hearing in the classroom in the absence of any routine audiological or language, learning or attention deficits to explain such a difficulty (SusCAPD group) on the LISN-S and a traditional CAPD test battery (Cameron & Dillon, 2008b). In order to study the effect of higher-order deficits on the LISN-S, a group of 11 children were also included in the study who presented with a range of documented learning or attention disorders, such as auditory memory deficits, dyslexia, specific language impairments and attention deficit hyperactivity disorder (LD group).

There were no significant differences on any LISN-S performance measure between the LD group and 70 age-matched controls (p ranging from 0.983 to 0.136). There were, however, significant differences between the SusCAPD group and the controls on all conditions where the physical location of the maskers was manipulated (p ranging from 0.001 to < 0.0001). This pattern of results, where an individual is outside normal limits only on the spatially-separated conditions of the LiSN-S (high cue SRT, spatial advantage and talker advantage), is defined as a spatial processing disorder (Cameron & Dillon, in press).

Only one child in the SusCAPD group and three children in the LD group were outside normal limits on one of the traditional (C)APD test battery assessment tools. Up to seven participants across groups were outside normal limits on one or more of the spatialized conditions of the LISN-S. The LISN-S did not correlate significantly with any of the assessment tools in the traditional CAPD test battery.

Box and whiskers plots below depict the median, inter quartile range and total range for all measures for (a) the SusCAPD group, and (b) the LD group in the Australian LISN-S CAPD study. The results are expressed as deviations of the scores for the children in SusCAPD and LD groups relative to the mean scores of children with normal hearing, expressed in units of standard deviations of the normative data, i.e. z scores. (Adapted from Cameron & Dillon, 2008b).

The results support the hypothesis that a high proportion of children with suspected CAPD have a deficit in the mechanisms that normally use the spatial distribution of sources to suppress unwanted signals. It could also be suggested that traditional CAPD test batteries may not identify children with an auditory stream segregation deficit.

A North American-accented version of the LISN-S (NA LiSN-S; Cameron & Dillon, 2009) has been developed in collaboration with the University of Cincinnati, the University of Texas at Dallas, and the Calgary Health Service. Some semantic items were changed to reflect North American dialogue and the sentences were recorded using native North American speakers. An initial study was conducted to determine the relative intelligibility of the LISN-S sentences and to adjust the level of the sentences for equal intelligibility. Post adjustment, intelligibility increased by 18.7 percent for each 1 dB increase in signal-to-noise ratio. Normative data was collected from 192 children and adults aged 6 to 30 years. Just as for the Australian data there was a trend of decreasing SRT and increasing advantage, as age increased across measures. No significant differences were found on any performance measure as a consequence of data collection site or gender. Inter - and intra-participant variation was minimal. Test-retest data was collected from 85 children and adults. Mean changes in performance on re-test on the NA LISN-S performance measures were minimal, ranging from 0.1 dB to 0.8 dB. Critical differences for test score improvements ranged from 3.0 dB to 4.4 dB (Cameron et al., 2009; Brown et al., 2010). The formulas used to determine the NA LiSN-S cut-off scores were adjusted, based on the data from Cameron, Glyde & Dillon (in press) so that adults aged up to 60 years can be assessed.

Both the Australian and North American versions of the LISN-S have been released commercially by Phonak Communication AG. (see https://www.phonakpro.com/com/b2b/en/professional_tools/diagnostic/lisn-s/lisn-s_in_detail.html.) The Australian-accented version of the LiSN-S is also distributed by Phonak in the United Kingdom.  Below is the results screen from the LiSN-S showing a profile typical of a spatial processing disorder.

References:

1. Cameron, S, Glyde, H & Dillon, H (in press). Listening in Spatialized Noise- Sentences Test (LiSN-S): Normative and retest reliability data for adolescents and adults up to 60 years of age. Journal of the American Academy of Audiology (Accepted 18 May 2011).

2. Cameron, S & Dillon, H (in press). Development and Evaluation of the LiSN & Learn Auditory Training Software for Deficit-Specific Remediation of Binaural Processing Deficits in Children: Preliminary Findings. Journal of the American Academy of Audiology (Accepted 29 April 2011).

3. Cameron, S, & Dillon, H (2010). LiSN & Learn Auditory Training Software (Version 1.1.0) [Computer software]. Sydney, NSW: National Acoustic Laboratories.

4. Brown, D, Cameron, S Martin, J, Watson, C, & Dillon, H (2010). The North American Listening in Spatialized Noise – Sentences Test (NA LiSN-S): Normative data and test-retest reliability studies for adolescents and young adults. Journal of the American Academy of Audiology, 21(10), 629-641.

5. Cameron ,S, Brown, D, Keith, R, Martin, J, Watson, C, & Dillon, H (2009). Development of the North American Listening in Spatialized Noise - Sentences Test (NA LISN-S): Sentence equivalence, normative data and test-retest reliability studies. Journal of the American Academy of Audiology, 20(2), 128-146.

6. Cameron, S & Dillon H (2009) Listening in Spatialized Noise – Sentences test (LISN-S) (Version 1.206) [Computer software]. Murten, Switzerland: Phonak Communications AG.

7. Cameron, S & Dillon, H (2008a). The Listening in Spatialized Noise – Sentences Test: Comparison to prototype LISN test and results from children with either a suspected (central) auditory processing disorder of a confirmed language disorder. Journal of the American Academy of Audiology, 19(5), 377-391.

8. Cameron, S & Dillon, H (2008b). Spatial hearing deficits as a major cause of auditory processing disorders: Diagnosis with the LISN-S and management options. In R. Seewald & J. Bamford, eds. A Sound Foundation Through Early Amplification 2007. Proceedings of the Fourth International Conference: Phonak AG, Switzerland, 235-241.

9. Cameron, S & Dillon, H (2007a). Development of the Listening in Spatialized Noise - Sentences Test (LISN-S). Ear and Hearing, 28(2), 196-211.

10. Cameron, S & Dillon, H (2007b). The Listening in Spatialized Noise - Sentences Test (LISN-S): Test-retest reliability study. International Journal of Audiology, 46, 145-153.