Authors' objectives:

The review was comprised of two areas of investigation and thus had two separate objectives. The first was to critically appraise evidence for the effect of classroom sound field amplification (SFA) on children's behavioural and learning outcomes. The second was to critically appraise the evidence examining the effectiveness of otoacoustic emissions (OAE) as a method of screening children for hearing impairments.

Authors' recommendations: Key results and conclusions Classroom sound field amplification Overall, evidence of the effect of sound field amplification on children's academic or behavioural performance is not strong for two main reasons, these being a lack of published studies and poor study design. Many of the studies promoting sound field amplification are unpublished or have been presented as conference papers only and so did not meet the criteria for inclusion in this technical brief. In addition, poor study design meant many of the published studies were susceptible to response bias. Several studies relied on class teachers to complete measures of children's behavioural or academic progress and these teachers were not blind to either the rationale of the study or the experimental condition. Teachers could potentially have been influenced by response and expectation bias making the results of these studies less convincing. The best evidence came from two longitudinal studies, one set in the United States and one in New Zealand. Improvements in children's learning and listening behaviours were seen in amplified classrooms. In the New Zealand study children who studied in classrooms with sound field amplification improved to a greater extent than children in unamplified classrooms in standardised tests of listening comprehension, reading comprehension and mathematics. The effect was the same for children with or without a history of middle ear disorders and for children from Pakeha or Maori ethnic groups. There was a trend for lower decile (lower SES) schools to improve more than high decile schools following sound field amplification but this was not significant. Unfortunately, analyses did not include direct comparisons of the control group and intervention group in either of these studies, so the results are less certain. There is a need for randomised controlled trials investigating the effect of both sound field amplification and classroom acoustic augmentation on children-s academic and behavioural performance before implementing amplification on a wide scale. Standardised academic measures or independent measures of behaviour, such as referrals for poor behaviour, should be utilised to avoid bias due to knowledge of the experimental condition. For measures where standardised assessments are not available independent observers blind to the experimental condition should be utilised. Otoacoustic emissions The lack of a true gold standard in audiometric testing of children resulted in studies using puretone audiometry, tympanometry, audiograms or a combination of pure-tone and tympanometry as a substitute gold standard, making comparison between the studies more difficult. Otoacoustic emission testing performed well relative to pure-tone audiometry with a high specificity and a good sensitivity. When compared to tympanometry, otoacoustic emission testing did not perform as well and sensitivity was lower. It may be that otoacoustic emissions are not as sensitive to hearing loss caused by middle ear disorders. In addition, variations between studies in the pass/fail criteria applied to otoacoustic emission, pure-tone and tympanometry tests may have affected test performance. Two studies manipulated the signal-to-noise ratio to determine the best pass/fail criteria for optimal OAE test performance in young children. The results of these studies suggest that the criteria used for infants and newborns may not be as appropriate for the assessment of young children's hearing. Optimal signal-to-noise ratios varied for different frequencies and varying the pass/fail criteria for different frequencies improved the sensitivity of the test. One study compared the performance of a test battery combining distortion-produced otoacoustic emissions with tympanometry with the commonly used pure-tone plus tympanometry battery. Further studies are needed to identify the optimal criteria for otoacoustic emission testing and how transient-evoked otoacoustic emissions perform in a test battery with tympanometry relative to a puretone/tympanometry test battery. It appears that otoacoustic testing would be especially suitable for hearing assessment in populations which are difficult to test using pure-tone audiometry, such as children with behavioural problems, or intellectual or physical impairments. It is, however, still subject to difficulties with a small number of children refusing to cooperate for both ears and testing sometimes being affected by ambient noise or breathing difficulties. No studies were identified which assessed the test performance of otoacoustic testing among difficult to test populations however initial feasibility studies have suggested there is potential for this to be successful. It would appear that otoacoustic emissions could be used to replace pure-tone testing in a test battery with tympanometry to screen for hearing loss but not to replace tympanometry. There is a need for community-based screening using the test battery and comparing it to a puretone/ tympanometry battery and further investigation of the performance of otoacoustic emission testing in difficult to test populations.

Authors' methods: Review

Project Status: Completed

URL for project: http://nzhta.chmeds.ac.nz/publications.htm

Year Published: 2007

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: New Zealand

Organisation Name: New Zealand Health Technology Assessment

Contact Address: Department of Public Health and General Practice, Christchurch School of Medicine and Health Sciences, University of Otago, P.O. Box 4345, Christchurch, New Zealand. Tel: +64 3 364 1145; Fax: +64 3 364 1152;

Contact Name: nzhta@chmeds.ac.nz

Contact Email: nzhta@chmeds.ac.nz

Copyright: New Zealand Health Technology Assessment (NZHTA)