Student working at a desk

Classroom Acoustics

Research summary

Because students on the autism spectrum process sensory input differently from students not on the spectrum, they often find classroom noise overwhelming. In particular, researchers have consistently found that students on the spectrum have significant difficulty processing speech in noise, affecting their capacity to follow instructions in noisy classrooms. Two studies conducted in special education classrooms have indicated that improved acoustics could significantly improve attention and reduce response times in students on the spectrum.

Research aim

This project compared the educational outcomes of students on the autism spectrum with those of age-, gender-, and classroom-matched students not on the spectrum when they are taught in:

  • a classroom without a sound field amplification ( SFA ) system
  • a classroom with an SFA system.

The project’s focus were educational outcomes, including students’:

  • listening to and comprehension of verbal instruction
  • attention to task
  • compliance with directions
  • report of ease of listening in the classroom
  • academic performance.

Associate professor and project leader Dr Wayne Wilson explains classroom acoustics.

Key elements

Classroom acoustics is how sound ‘behaves’ in the classroom. Classroom acoustics affect how well students can hear in the classroom. Some terms to be aware of:

  • Unoccupied sound level : The sound in the classroom when it is empty. This sound level is usually reported in A-weighted decibels (dBA). Australian Standards recommend unoccupied sound levels in classrooms should be below 35–45 dBA. 35 dB is about the level of a whisper.
  • Occupied sound level : The sound in the classroom when students and teachers are present. This sound level is usually reported in A-weighted decibels (dBA). Australian Standards recommend unoccupied sound levels in classrooms should be below 50–60 dBA. 50 dB is about the level of someone who is speaking in a normal conversational voice.
  • Reverberation time ( RT ): The time taken for sound to decrease in the classroom – specifically, the time taken for a briefly played sound to decay by 60 dB. Australian Standards recommend RTs in classrooms should be below 0.3–1.2 seconds from small to large classrooms. Higher RTs make a room sound echoey.
  • Speech transmission index ( STI ): An estimate of how easy it is to hear speech sounds in a classroom. The STI ranges from 0 (no speech sounds would be heard) to 1 (all speech sounds would be heard).
  • Signal-to-noise ratio ( SNR ): The ratio of the level of a desired signal to the level of the noise – e.g. the level of the teacher’s voice to the level of general background noise. When represented in decibels, the SNR can be conveniently calculated as the difference between the signal and noise levels. 

In Australia and New Zealand, acoustic standards and recommendations for primary school teaching spaces or single classrooms include:  

  • unoccupied sound levels of <35 dB LAeq and RTs of <0.3 s to 1.2 s (depending on room size)
  • occupied sound levels of <50 dB LAeq
  • STI values of >0.75 for classrooms containing younger primary school children and >0.60 for classrooms containing older primary school children. 

In Australia and New Zealand, recommendations for the acoustic measures listed above can be drawn from two sources: 

  • Australian/New Zealand Standard 2107: Acoustics – Recommended design sound levels and reverberation times for building interiors (AS/NZS 2107:2016) 
  • Classroom acoustic conditions: Understanding what is suitable through a review of national and international standards, recommendations, and live classroom measurements (Mealings, 2016).

Poor classroom acoustics negatively affects student performance, including students’:  

  • speech reception
  • speech perception
  • reading and language comprehension
  • linguistic and cognitive processing
  • cognition, concentration, psychoeducational, and psychosocial achievement.

The impact is greater for students on the autism spectrum.

Teachers can also be affected by the need to raise their voices for extended periods, which can lead to vocal strain.

One way to improve classroom acoustics is to improve the SNR in the classroom.

The SNR in classrooms can be improved through:

  • SFA systems
  • personal sound amplification 
  • acoustically treating classrooms. 

Improved SNR is reported to support all students, including students on the spectrum. 

Quick reference guide

Classroom acoustics: Quick reference guide

Our evidence base

Aim

This review of the literature aimed to determine if improving the signal-to-noise ratio ( SNR ) improves classroom performance in students on the spectrum.

Method

Six databases were searched using the search terms ‘acoustics’, ‘signal-to-noise ratio’, ‘classroom’, and ‘ASD’. 

To be included in the literature review, the studies had to:

  • include students on the spectrum with or without other developmental conditions such as ADD/ADHD (if the study included students with conditions other than autism, it must have reported data for the students on the spectrum separately)
  • enhance the SNR through device (e.g. personal sound amplification or sound field amplification ( SFA )) or environmental (e.g. acoustic treatment of the classroom) modifications
  • compare treatment versus no treatment conditions 
  • measure any aspect of student listening and/or classroom performance.

Five studies were found that met the selection criteria.

Results

All five studies reported that improving SNR improved classroom performance in students on the spectrum.

Three studies with 29 participants in total reported that using personal FM systems resulted in improvements in areas including: 

  • listening 
  • auditory performance 
  • communication 
  • speech recognition in noise  
  • on-task behaviours 
  • auditory filtering 
  • effects of noise and reverberation  
  • aversiveness to sound 
    (Rance et al., 2014; Schafer et al., 2013; Schafer et al., 2016).

One study reported no significant improvements in:

  • listening comprehension  
  • auditory memory
    (Schafer et al., 2016).

One study with 10 participants reported that SFA systems reduced listening stress (Rance et al., 2017).

One study with three participants reported that sound-absorbing walls decreased nonattending and inattentive behaviours (Kinnealey et al., 2012).

Conclusion and limitations

The review suggests: 

  • improving the SNR leads to improved classroom performance in students on the spectrum compared to no intervention
  • the most effective way to improve the SNR is by using personal FM systems.

The conclusions of this review were limited by the:

  • small number of studies that met the selection criteria
  • lack of randomised controlled trials
  • lack of explicit descriptions of autism diagnoses 
  • small number of students in the studies
  • student and teacher bias when completing questionnaires
  • low response rate from teachers on questionnaires
  • lack of diversity in studies, which did not always include students on the spectrum with greater support needs. 
Aim

The aim of this study was to determine if the classroom acoustics of a large sample of primary school classrooms in and around Brisbane, Australia, complied with relevant Australian and New Zealand standards (Standards Australia Limited/Standards New Zealand, 2016) and recommendations (Mealings, 2016).

Method

For this study, measurements were taken of:

  • the unoccupied sound level and reverberation time ( RT ) in 33 primary school (Year 3) classrooms 
  • the occupied sound level and STI in 12 of the 33 classrooms.
  • All three education sectors in the region were represented: 
  • Department of Education: 3 schools, 7 classrooms
  • Brisbane Catholic Education: 5 schools, 8 classrooms 
  • Independent Schools Queensland: 5 schools, 18 classrooms. 

The classrooms were chosen by the school principal and were ‘typical’ for the region. They were:

  • single-cell classrooms, or dual-cell classrooms separated by a concertina divider 
  • generally large – between 69 to 378 m3 in volume 
  • made predominantly from acoustically hard materials, including concrete, brick, plaster, wood and glass.
Results

All 33 classrooms

Unoccupied sound levels ranged from 25.7 to 50.0 dB LAeq. This was a 26% failure rate against Australian Standards for unoccupied sound level of teaching spaces in primary school classrooms.

RTs ranged from 0.34 to 1.26 s. This was a 79% failure rate against RTs for Australian Standards for teaching spaces in primary school classrooms. 

12 classrooms – further measurements

Occupied sound levels ranged from 49.8 to 64.8 dB LAeq during quiet activity. STI values ranged from 0.35 to 0.80 (on a scale of 0 to 1). This represented a 92% failure rate against research recommendations for teaching spaces in primary school classrooms in Australia.

Conclusion and limitations

The ‘acoustic health’ of the 33 primary school classrooms in the study was generally poor but similar to that seen in classrooms around the world. 

The poor acoustic health was most likely due to the design and build of these classrooms. The classrooms would likely benefit from routine measurement of their acoustics and the implementation of standard methods to improve those acoustics. 

The trialling of SFA was also deemed to be a viable option for these classrooms.

Aim

This study aimed to determine whether SFA can support students on the spectrum in the areas of: 

  • auditory attention
  • auditory memory
  • phonological processing in quiet and noise
  • educational achievement in literacy and numeracy.
Method

A trial was conducted with students in Year 3 from 12 primary schools in and near Brisbane, Australia. The sample consisted of:

  • 13 students on the spectrum (9 males, aged 7.6 to 8.4 years)
  • 17 students not on the spectrum (7 males, aged 7.6 to 9.3 years).

All students had an SFA system in their classroom for one semester of the same school year.

  • 17 students (a mix of students on the spectrum and not on the spectrum) had an SFA system in their classrooms in semester one.
  • 13 students (a mix of students on the spectrum and not on the spectrum) had an SFA system in their classrooms in semester two.
Results

The short-term use of SFA in classrooms could assist students on the spectrum to improve their skills in some areas of phonological processing (nonword blending) in quiet and noise. However, SFA did not assist students in other areas of phonological processing (nonword repetition) in quiet and noise, or in areas of academic performance, attention, or memory. 

Conclusion and limitations

The study suggests that one semester of SFA could improve the learning of students on the spectrum, but does not guarantee immediately improved learning.

SFA helped students on the spectrum to more clearly and consistently hear the phonemes spoken by their teachers in their classrooms over the course of a semester. This led to students improving their skills in some areas of phonological processing (nonword blending). By making hearing easier, SFA could allow students to focus on phonological processing. 

The conclusions of this review were limited by the:

  • small sample sizes
  • inconsistent pairing of students on the spectrum and not on the spectrum
  • use of standardised measures of cognition and educational performance, which could have missed functional gains from SFA
  • short-term use of SFA (single semester only), which could have missed benefits from longer term use of SFA
  • group comparisons, which limit the ability to interpret results of individual students.

The results are restricted to students who are like those in the study – students in mainstream schools who are required to complete lengthy assessment.

Meet the researchers

Dr Rebecca Armstrong

University of Queensland

Cerys Downing

Dr Keely Harper-Hill

Queensland University of Technology

Kelsey Perrykkad

Dr Wayne Wilson

Dr Jill Ashburner

Autism Queensland

Publications from this project

Van der Kruk, Y., Wilson, W.J., Downing, C., Palghat, K., Harper-Hill, K., & Ashburner, J. (2017). Improved signal-to-noise ratio and classroom performance in children with Autism Spectrum Disorder: A systematic review. Review Journal of Autism and Developmental Disorders, 4(3), 243–253.

Wilson, W.J., Downing, C., Perrykkad, K., Armstrong, R., Arnott, W.L., Ashburner, J., & Harper-Hill, K. (Submitted). The 'acoustic health' of primary school classrooms in Brisbane, Australia. Speech, Language and Hearing. doi:10.1080/2050571X.2019.1637042 

Wilson, W.J., Harper-Hill, K., Armstrong, R., Downing, C., Perrykkad, K., & Ashburner, J. (nd). Soundfield amplification for primary school students on the autism spectrum: standardised measures, Journal of Autism and Developmental Disorders.

Articles informing this project

Anderson, K. (2001). Kids in noisy classrooms: what does the research really say? Journal of Educational Audiology, 9, 21–33.

Bennetts, L. K., & Flynn, M. C. (2002). Improving the classroom listening skills of children with Down syndrome by using soundfield amplification. Down's Syndrome, Research and Practice, 8, 19–24.

Berg, F. S., Blair, J. C., & Benson, P. V. (1996). Classroom acoustics: The problem, impact, and solution. Language, Speech, and Hearing Services in Schools, 27(1), 16–20.

Blake, R., Field, B., Foster, C., Platt, F., & Wertz, P. (1991). Effect of FM auditory trainers on attending behaviors of learning-disabled children. Language, Speech, and Hearing Services in Schools, 22, 111–114.

Bolt, R. H., & Macdonald, A. D. (1949). Theory of speech masking by reverberation. Journal of the Acoustical Society of America, 21(6), 577–580. doi:10.1121/1.1906551

Cassidy, G., & MacDonald, R. A. R. (2007). The effect of background music and background noise on the task performance of introverts and extraverts. Psychology of Music, 35(3), 517–537. doi:10.1177/0305735607076444

Crandell, C., & Smaldino, J. J. (2000). Classroom acoustics for children with normal hearing and with hearing impairment. Language Speech and Hearing Services in Schools, 31(4), 362–370. doi:10.1044/0161-1461.3104.362

Dockrell, J. E., & Shield, B. (2012). The impact of sound-field systems on learning and attention in elementary school classrooms. Journal of Speech Language and Hearing Research, 55(4), 1163–1176. doi:10.1044/1092-4388(2011/11-0026)

Dockrell, J. E., & Shield, B. M. (2006). Acoustical barriers in classrooms: The impact of noise on performance in the classroom. British Educational Research Journal, 32(3), 509–525. doi:10.1080/01411920600635494

Finitzo-Hieber, T., & Tillman, T. W. (1978). Room acoustics effects on monosyllabic word discrimination ability for normal and hearing-impaired children. Journal of Speech and Hearing Research, 21(3), 440–458.

Flexer, C., Millin, J. P., & Brown, L. (1990). Children with developmental disabilities: The effect of sounds filed amplification on word identification. Language, Speech, and Hearing Services in Schools, 21, 177–182.

Gotaas, C., & Starr, C. D. (1993). Vocal fatigue among teachers. Folia Phoniatrica, 45(3), 120–129. doi:10.1159/000266237

Greenland, E. E., & Shield, B. M. (2011). A survey of acoustic conditions in semi-open plan classrooms in the United Kingdom. Journal of the Acoustical Society of America, 130(3), 1399–1410. doi:10.1121/1.3613932

Johnston, K. N., John, A. B., Kreisman, N. V., Hall, J. W., & Crandell, C. C. (2009). Multiple benefits of personal FM system use by children with auditory processing disorder (APD). International Journal of Audiology, 48(6), 371–383.

Keith, R. W. (1999). Clinical issues in central auditory processing disorders. Language, Speech, and Hearing Services in Schools, 30, (339–344).

Klatte, M., Lachmann, T., & Meis, M. (2010). Effects of noise and reverberation on speech perception and listening comprehension of children and adults in a classroom-like setting. Noise & Health, 12(49), 270–282. doi:10.4103/1463-1741.70506

Lochner, J. P. A., & Burger, J. F. (1964). Influence of reflections on auditorium acoustics. Journal of Sound and Vibration, 1(4), 426–454. doi:10.1016/0022-460x(64)90057-4

Massie, R., & Dillon, H. (2006). The impact of sound-field amplification in mainstream cross-cultural classrooms: Part 1 – Educational outcomes. Australian Journal of Education, 50(1), 62–77.

Maxwell, L. E., & Evans, G. W. (2000). The effects of noise on pre-school children's pre-reading skills. Journal of Environmental Psychology, 20(1), 91–97. doi:10.1006/jevp.1999.0144

Mealings, K. T. (2016, 9-11 November 2016). Classroom acoustic conditions: Understanding what is suitable through a review of national and international standards, recommendations, and live classroom measurements. Paper presented at the Acoustics 2016, Brisbane, Australia.

Mealings, K. T., Buchholz, J. M., Demuth, K., & Dillon, H. (2015). Investigating the acoustics of a sample of open plan and enclosed Kindergarten classrooms in Australia. Applied Acoustics, 100, 95–105. doi:10.1016/j.apacoust.2015.07.009

Nabelek, A. K., & Pickett, J. M. (1974). Reception of consonants in a classroom as affected by monaural and binaural listening, noise, reverberation, and hearing-aids. Journal of the Acoustical Society of America, 56(2), 628–639.

Nelson, P. B., & Soli, S. (2000). Acoustical barriers to learning: Children at risk in every classroom. Language Speech and Hearing Services in Schools, 31(4), 356–361. doi:10.1044/0161-1461.3104.356

Nelson, P. B., Kohnert, K., Sabur, S., & Shaw, D. (2005). Classroom noise and children learning through a second language: Double Jeopardy? Language Speech and Hearing Services in Schools, 36(3), 219–229. doi:10.1044/0161-1461(2005/022)

Reynolds, S., Kuhaneck, H. M., & Pfeiffer, B. (2016). Systematic review of the effectiveness of frequency modulation devices in improving academic outcomes in children with auditory processing difficulties. American Journal of Occupational Therapy, 70(1), doi:10.5014/ajot.2016.016832

Ronsse, L. M., & Wang, L. M. (2013). Relationships between unoccupied classroom acoustical conditions and elementary student achievement measured in eastern Nebraska. Journal of the Acoustical Society of America, 133(3), 1480–1495. doi:10.1121/1.4789356

Schafer, E. C., Traber, J., Layden, P., Amin, A., Sanders, K., Bryant, D., & Baldus, N. (2014). Use of wireless technology for children with auditory processing disorders, attention-deficit hyperactivity disorder, and language disorders. Seminars in Hearing, 35(3), 193–205.

Seibein, G. W., Gold, M. A., Siebein, G. W., & Ermann, M. G. (2000). Ten ways to provide a high-quality acoustical environment in schools. Language, Speech, and Hearing Services in Schools, 31, 376–384.

Shield, B., & Dockrell, J. E. (2003). The effects of noise on children at school: a review. Building Acoustics, 2, (97–116).

Shield, B., Greenland, E., & Dockrell, J. (2010). Noise in open plan classrooms in primary schools: A review. Noise & Health, 12(49), 225–234. doi:10.4103/1463-1741.70501

Smaldino, J. J., & Crandell, C. C. (2000). Classroom amplification technology: Theory and practice. Language Speech and Hearing Services in Schools, 31(4), 371–375. doi:10.1044/0161-1461.3104.371

Smith, E., Gray, S. D., Dove, H., Kirchner, L., & Heras, H. (1997). Frequency and effects of teachers' voice problems. Journal of Voice, 11(1), 81–87. doi:10.1016/S0892-1997(97)80027-6

Updike, C. D. (2006). The use of FM systems for children with attention deficit disorder. Journal of Educational Audiology, 13, 7–14.

Vickers, D. A., Backus, B. C., Macdonald, N. K., Rostamzadeh, N. K., Mason, N. K., Pandya, R., . . . Mahon, M. H. (2013). Using personal response systems to assess speech perception within the classroom: An approach to determine the efficacy of sound field amplification in primary school classrooms. Ear and Hearing, 34(4), 491–502. doi:10.1097/AUD.0b013e31827ad76f

Wilson, W. J., Marinac, J., Pitty, K., & Burrows, C. (2011). The use of sound-field amplification devices in different types of classrooms. Language Speech and Hearing Services in Schools, 42(4), 395–407. doi:10.1044/0161-1461(2011/09-0080)

Young, D., Bradle, P., Hickson, L., & Lawson, M. (1997). Preferred FM system listening levels of children with central auditory processing disorders. Journal of the Academy of Rehabilitative Audiology, 30, 53–61.

Practices