Starkey Research & Clinical Blog

Impact of Classroom Noise on Children’s Listening

Listening Effort at Signal-to-Noise Ratios that are Typical of the School Classroom

Howard, C. S., Munro, K. & Plack, C. J. (2010). Listening effort at signal-to-noise ratios that are typical of the school classroom.  International Journal of Audiology, 49, 928-932.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

Everyday activities often require attention to more than one concurrent task. The ability to do this successfully depends on a number of factors; including distractions, the difficulty of the tasks and the perceived importance of the tasks.  In a classroom, children regularly have to attend to multiple tasks at the same time. For instance, they may be taking notes and reading information on a board or a computer screen, while also listening to the teacher and comments or questions from other students. To complicate matters, these tasks are often carried out in the presence of varying levels of background noise.

Classroom noise has a detrimental effect on learning (Shield & Dockrell, 2003). Completing more than one task at a time in a noisy place may adversely affect learning because it requires greater listening effort on behalf of the student.  In other words, in the presence of background noise and when attending to multiple tasks, greater cognitive resources must be dedicated to understanding speech. This means that performance on one or more of the tasks, including comprehension of the spoken lesson, can deteriorate.  Classroom signal to noise ratios (SNRs) have been measured in the range of -7dB to +5dB (Arnold & Canning, 1999; Crandell & Smaldino, 1995, 2000). Low SNRs are known to have a particularly detrimental effect on speech perception for hearing-impaired listeners, especially children (Blandy & Lutman, 2005; Jamieson et al. 2004). Therefore, the effect of SNR on listening effort and classroom multi-tasking are of special concern for hearing-impaired students.

Listening effort can be measured in adults with self-report ratings, in children it is usually measured with dual-task paradigms. Hicks and Tharpe (2002) compared the performance of children with mild hearing loss to that of normal hearing children in a dual-task study. The primary task was word recognition at 70dB in quiet and in multi-talker babble at SNRs of +10dB to +20dB. The secondary task measured visual reaction time to randomly presented lights. The authors found that reaction time was longer for the hearing-impaired children than for the normal-hearing children, suggesting that the hearing-impaired children required more listening effort, therefore devoting fewer cognitive resources to the secondary task.  Interestingly, there was no significant effect of SNR on listening effort. 

McFadden & Pittman (2008) conducted a dual-task experiment with hearing-impaired and normal-hearing 8-12 year olds. The primary task was to categorize words, presented in quiet and in noise at SNRs or 0dB and +6dB. The secondary task involved completion of a dot-to-dot puzzle.  Performance on the secondary task decreased when both tasks were performed together, though there was no significant effect of hearing loss or SNR.

The authors of the current study surmised that the SNRs used in previous studies were too favorable and did not represent typical classroom SNRs. SNR may indeed have a detrimental effect on multi-tasking, but the SNRs used in previous experiments might not have been sufficiently challenging to yield an effect.  The study summarized in this blog post aimed to measure listening effort in a dual task paradigm using SNRs that were more typical of classroom environments. The authors hypothesized that as SNR decreased, listening effort would increase, yielding poorer performance on the secondary task.  Thirty-one normal-hearing children, age 9-12 years, participated in the study. None of the subjects had any history of hearing loss or communication or learning disabilities.

The primary task was a word recognition test using consonant-vowel-consonant monosyllables (Boothroyd, 1968). Words were spoken by a male speaker at 65dB and presented binaurally via headphones. Each set of words was mixed with multi-speaker babble which had been recorded from children’s background chatter (Hamilton, 2008), which the authors deemed most similar to typical classroom background noise.  The level of babble was adjusted to create four SNR conditions: quiet, +4dB, 0dB and -4dB. The secondary task involved rehearsing sets of 5 visually-presented digits and reciting them at a later time. Each task was presented alone and together in a dual-task condition. In the dual-task condition, the string of 5 digits was presented for 3 seconds. Then, a set of 5 words was presented and scored before the subjects were asked to recall the rehearsed digits.

For performance on the primary task, the authors found a significant effect of SNR and task combination, as well as a significant interaction between SNR and task combination. In other words, performance on the word recognition task deteriorated when combined with the digit recall task, and also deteriorated with decreasing SNR.  Even more deterioration in performance was noted in the dual task condition when SNR decreased. 

For performance on the secondary task, there was less of an effect of SNR in the single task condition, suggesting that subjects were able to ignore the background noise successfully as they completed the visual recall task.  For the dual task condition, digit recall performance decreased significantly, especially for lower SNRs.  There was a strong, significant interaction between SNR and task combination, showing that performance decreased more substantially in the dual task condition when SNRs were lower.

As expected, mean performance on the word recognition test decreased with lower SNRs. In general, the dual task condition yielded similar word recognition performance, but for lower SNRs, performance on the secondary task deteriorated, supporting the hypothesis that increased listening effort was required for multi-tasking in the presence of increasing background noise. This is consistent with results found for adult subjects, in which decreased performance on a secondary reaction-time task was found when noise was added to the primary listening task (Downs & Crum, 1978).

All test stimuli used in the current experiment were presented under headphones. This test condition removes acoustic cues that would be experienced in the classroom where there is spatial separation between primary and secondary speech stimuli.  Future work with hearing-impaired children listening in a spatially distributed sound field would more closely approximate a classroom environment.  Additionally, the use of hearing aids with directional microphones and FM systems may reduce some deleterious effects of SNR. Further research is needed to illuminate the interactions among these variables. 

The current study showed a clear deterioration in secondary task performance as the SNR decreased, suggesting that increased listening effort was required in conditions with poorer SNRs. This has important implications for classroom environments, in which children are regularly required to listen and perform secondary tasks such as taking notes and reading visual materials.  As classroom background noise increases, children are likely to have fewer cognitive resources available to attend to the spoken lesson, take notes and participate in discussions.  Decreases in classroom noise levels may be achieved in many ways, including classroom architecture and design, the use of acoustic damping and noise reduction materials and organization of students’ workstations.

These observations have particular importance for hearing-impaired students, who are more likely to suffer deleterious effects of classroom background noise.  Although this study did not include hearing-impaired listeners, the findings support the continued recommendation of preferential seating, FM systems and other efforts to improve signal to noise ratio in the classroom.

References

Arnold, P. & Canning, D. (1999). Does classroom amplification aid comprehension? British Journal of Audiology, 33, 171-178.

Blandy, S. & Lutman, M. (2005). Hearing threshold levels and speech recognition in noise in 7-year-olds. International Journal of Audiology, 44, 435-443.

Boothroyd, A. (1968). Developments in speech audiometry. British Journal of Audiology, 2, 3-10.

Crandell, C.C. & Smaldino, J.J. (1995). Speech perception in the classroom. In: C. Crandell, J. Smaldino & C. Flexer (eds.), Sound-field FM Amplification: Theory and Practical Applications. San Diego, California: Singular Publication Group.

Crandell, C.C. & Smaldino, J.J. (2000). Classroom acoustics for children with normal hearing and with hearing impairment.  Language, Speech and Hearing Services in Schools, 31, 362-370.

Downs, D.W. & Crum, M.A. (1978). Processing demands during auditory learning under degraded listening conditions. Journal of Speech and Hearing Research, 21, 702-714.

Hamilton, G. (2008). Compressed Babble for Speech-in-Noise Testing. Available from: The Ewing Foundation in association with the University of Manchester. www.ewing-foundation.org.uk/.

Hicks, C.B. & Tharpe, A.M. (2002). Listening effort and fatigue in school-age children with and without hearing loss. Journal of Speech, Language and Hearing Research, 45, 573-584.

Howard, C. S., Munro, K. & Plack, C. J. (2010). Listening effort at signal-to-noise ratios that are typical of the school classroom.  International Journal of Audiology, 49, 928-932.

Jamieson, D.G., Kranjc, G., Yu, K. (2004). Speech intelligibility of young school-aged children in the presence of real-life classroom noise. Journal of the American Academy of Audiology, 15, 508-517.

McFadden, B. & Pittman, A. (2008). Effect of minimal hearing loss on children’s ability to multitask in quiet and in noise. Language, Speech and Hearing Services in Schools, 39, 342-351.

Shield, B.M. & Dockrell, J.E. (2003). The effects of noise on children at school: A review. Journal of Building Acoustics, 10, 97-106.