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.
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.
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 occupied 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.
This review of the literature aimed to determine if improving the signal-to-noise ratio ( SNR ) improves classroom performance in students on the spectrum.
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.
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:
- auditory performance
- 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.
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).
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.
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.
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.
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.
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.
Dr Rebecca Armstrong
Dr Keely Harper-Hill
Dr Wayne Wilson
Dr Jill Ashburner
All researcher details including names, honorifics (for example ‘Dr’), and organisational affiliations are correct at the time of the project.
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