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Combined Effects of Noise and Reverberation on Speech Recognition Performance of Normal-Hearing Children and Adults

Neuman, Arlene C.1; Wroblewski, Marcin1; Hajicek, Joshua1; Rubinstein, Adrienne1,2

doi: 10.1097/AUD.0b013e3181d3d514
Research Articles

Objectives: The purpose of this study is to determine how combinations of noise levels and reverberation typical of ranges found in current classrooms will affect speech recognition performance of typically developing children with normal speech, language, and hearing and to compare their performance with that of adults with normal hearing. Speech recognition performance was measured using the Bamford-Kowal-Bench Speech in Noise test. A virtual test paradigm represented the signal reaching a student seated in the back of a classroom with a volume of 228 m3 and with varied reverberation time (0.3, 0.6, and 0.8 sec). The signal to noise ratios required for 50% performance (SNR-50) and for 95% performance were determined for groups of children aged 6 to 12 yrs and a group of young adults with normal hearing.

Design: This is a cross-sectional developmental study incorporating a repeated measures design. Experimental variables included age and reverberation time. A total of 63 children with normal hearing and typically developing speech and language and nine adults with normal hearing were tested. Nine children were included in each age group (6, 7, 8, 9, 10, 11, and 12 yrs).

Results: The SNR-50 increased significantly with increased reverberation and decreased significantly with increasing age. On average, children required positive SNRs for 50% performance, whereas thresholds for adults were close to 0 dB or <0 dB for the conditions tested. When reverberant SNR-50 was compared with adult SNR-50 without reverberation, adults did not exhibit an SNR loss, but children aged 6 to 8 yrs exhibited a moderate SNR loss and children aged 9 to 12 yrs exhibited a mild SNR loss. To obtain average speech recognition scores of 95% at the back of the classroom, an SNR ≥10 dB is required for all children at the lowest reverberation time, of ≥12 dB for children up to age 11 yrs at the 0.6-sec reverberant condition, and of ≥15 dB for children aged 7 to 11 yrs at the 0.8-sec condition. The youngest children require even higher SNRs in the 0.8-sec condition.

Conclusions: Results highlight changes in speech recognition performance with age in elementary school children listening to speech in noisy, reverberant classrooms. The more reverberant the environment, the better the SNR required. The younger the child, the better the SNR required. Results support the importance of attention to classroom acoustics and emphasize the need for maximizing SNR in classrooms, especially in classrooms designed for early childhood grades.

A virtual classroom test paradigm was used to determine how elementary school children's (ages 6-12) speech recognition in noise is affected by reverberation typical of current classrooms (RT = 0.3, 0.6, and 0.8 s) as compared with adult performance. Signal-to-noise ratios required for 50% performance significantly increased with increased reverberation and decreased age. Findings support continuing efforts to control background noise levels and reverberation in classrooms. SNRs required for optimum speech recognition (95%) of elementary school children exceed the typical SNRs found in occupied elementary school classrooms.

1Department of Otolaryngology, New York University School of Medicine, New York, New York; and 2Department of Speech Communication Arts and Sciences, Brooklyn College, CUNY, Brooklyn, New York.

This work was supported by the National Institute on Disability and Rehabilitation Research. The contents of this paper were developed under a grant from the Department of Education, NIDRR grant number H133E030006. However, those contents do not necessarily represent the policy of the Department of Education, and you should not assume endorsement by the Federal Government. Etymotic Research provided ER6i earphones and ear tips for testing.

Portions of this study were presented in a poster at the 2009 meeting of the American Academy of Audiology.

Address for correspondence: Arlene C. Neuman, PhD, NYU School of Medicine, Department of Otolaryngology, 550 First Avenue, NBV 5E5, New York, NY 10016. E-mail:

Received October 14, 2009; accepted December 23, 2009.

© 2010 Lippincott Williams & Wilkins, Inc.