1 Introduction

University is an important time for students. It is where they work towards obtaining a tertiary degree to open up opportunities for future employment, prepare for work, contribute to the social, cultural, economic and political enrichment of society, and contribute to their own well-being [1]. Therefore, it is vital that higher education spaces are accessible to all and are places that promote equity and inclusion.

A recent review revealed that poor classroom acoustic conditions can negatively affect university students’ listening, learning, and well-being [2]. For example, higher noise levels can negatively affect students’ speech intelligibility [3, 4], listening effort [5], listening comprehension [6, 7], word recall [8], concentration [9, 10], memory [11], academic acheivement [12, 13], and satisfaction [14, 15]. Additionally, long reverberation times can negatively impact students’ speech intelligilbilty [16], listening effort [17], listening comprehension [6, 7, 18], attention [19], memory [11], and academic acheivement [12,13,14].

Poor acoustic conditions are problematic for all students, but are likely to be especially an issue for those with communication difficulties or hearing sensitivities who have a listening disadvantage and need better acoustic conditions [20]. Studies with primary school children have shown poor acoustic conditions to be particularly problematic for children with hearing loss, autism, or attention deficit hyperactivity disorder [21,22,23,24]. Poor acoustic conditions are also detrimental for those who are non-native listeners [16, 25], which is problematic given that international students are common at universities. Additionally, it is not only the students who are likely to suffer, but also the teachers, especially if they have any communication, sensory, or language difficulties. Poor acoustic conditions can also be problematic for teachers’ vocal health from the need to raise their voice above a comfortable level [26, 27]. Therefore, it is important that the acousic conditions of university classrooms are adequate to ensure that they are accessible to all students and teachers, and promote their listening, learning, and well-being. The aim of this study was to measure the unoccupied noise levels and reverberation times of all of the classrooms in an Australian university as an example of the current acoustic accessibility and identify where the shortfalls are. This will provide information for future projects to improve accessibility so that all students and teachers can flourish.

2 Method

2.1 Campus

Macquarie University was chosen as the campus to take the measurements. Macquarie University is located in Sydney, New South Wales, Australia. The main campus (Wallumattagal Campus) is located in Macquarie Park, 15 kms from Sydney's city centre (hence is a quieter location), in one of the largest business and technology precincts in the Southern Hemisphere. It was first built in the late 1960s and early 1970s, but several buildings have been built or refurbished since then. Around 44,000 students attend the main campus from more than 100 different countries. There are around 3,000 staff members. Macquarie University is in the top 1% of universities in the world [28]. A total of 166 out of the 169 classrooms available at the university at the time were measured for this study.

2.2 Acoustic Measures

Unoccupied background noise levels and unoccupied reverberation times were measured in the university classrooms using the ListenApp for Schools on an iPad Pro running software version 13.4.1. The ListenApp for Schools uses the same backend as the SoundOut Room Acoustics Analyser app which has been validated on an iPad Air against a sound level meter [29]. Three measurements of the noise levels and reverberation times were taken in each classroom—one measurement at the front, one in the middle, and one at the back. The average of the three measurements was then used in the data analysis.

2.3 Macquarie University Design Guidelines

Macquarie University has its own acoustic design standards called the MQU Design Guidelines Review Performance Standards [30]. For classrooms, the recommended noise level is 35 dBA (low) and 40 dBA (high), and reverberation times are recommended to be within 0.4–0.6 s. These are similar to the Australian/New Zealand Standard [31]. These are the guidelines that the traffic light system of good, ok, and poor classrooms is based on for this study.

2.4 Data Analysis

Data were collated and organised in Microsoft Excel. Correlations were run using R Studio 2023.06.1 using R version 4.2.1.

3 Results

3.1 Unoccupied Background Noise Levels

Figure 1 shows the unoccupied background noise levels of the measured classrooms in order of the rooms with the lowest noise level to the highest noise level. The data points are colour-coded according to the Macquarie University design guidelines. The results revealed that 52% of classrooms were within the recommended < 35 dBA limit (good), 20% were within the 35–40 dBA maximum limit (ok) and 27% were above the 40 dBA limit (poor). The high noise levels in classrooms were due to loud air-conditioning systems.

Fig. 1
figure 1

Unoccupied background noise levels of the measured classrooms in order of the rooms with the lowest noise level to the highest noise level. Data points are colour-coded by the following key: green = good, orange = ok, red = poor

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3.2 Unoccupied Reverberation Times

Figure 2 shows the unoccupied reverberation times of the measured classrooms in order of the rooms with the lowest reverberation time to the highest reverberation time. The data points are colour-coded according to the Macquarie University design guidelines. The results revealed that 65% of classrooms were within the recommended 0.4–0.6 s limit (good), 6% were < 0.4 s (we still mark this as good but it should be noted that this is on the lower end as some reverberation is helpful for comfortable speech production) and 29% were above the 0.6 s limit (poor). Figure 2 shows that there is a steady increase in non-compliant reverberation times from 0.6 to 0.7 s, then a sharper increase from 0.7 s upwards, with two classrooms that are particularly poor are around 1.3 s.

Fig. 2
figure 2

Unoccupied reverberation times of the measured classrooms in order of the rooms with the lowest reverberation time to the highest reverberation time. Data points are colour-coded by the following key: green = good, red = poor

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3.3 Combined Noise and Reverberation Results

Figure 3 shows the combined unoccupied noise level and unoccupied reverberation times of the measured classrooms. The data points are colour-coded according to the Macquarie University design guidelines, where green means both measures were good, orange means one measure was good but one measure was ok, and red means that at least one measure was poor. The results revealed that 40% of classrooms were good, 13% were ok, and 48% were poor.

Fig. 3
figure 3

Combined unoccupied background noise levels and reverberation times of the measured classrooms. Data points are colour-coded by the following key: green = good, orange = ok, red = poor

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3.4 Correlations with Room Floor Area

Figure 4 shows the correlations of the measured reverberation times with the floor area of the classroom. Floor area was not significantly correlated with reverberation time (r = 0.15, p < 0.051).

Fig. 4
figure 4

Correlations of the measured reverberation times with the floor area of the classroom. Data points are colour-coded by the following key: green = good, red = poor

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3.5 Categorisation by Year Built/Refurbished

Figure 5 shows the (a) unoccupied background noise levels and (b) unoccupied reverberation times categorised by the year on record that the building was built or when the classrooms were refurbished. For the noise levels, there is a trend of a lower level the more recent the building. A trend cannot be seen for reverberation times, however. The main points to note for reverberation times are that there was a big spread for classrooms built in the early 1970s, and that reverberation times were particularly high for the classrooms refurbished in 2010.

Fig. 5
figure 5

Results of the measured classrooms (a) unoccupied background noise levels and (b) unoccupied reverberation times categorised by the year built or refurbished. Classrooms in buildings where dates were not able to be found come under “unknown”

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4 Discussion

The aim of this study was to measure the unoccupied noise levels and reverberation times of all the classrooms in an Australian university to assess the current acoustic accessibility and plan how to make the campus more accessible so that all students and teachers can flourish. The results revealed that 40% of classrooms met both the noise level and reverberation time limits recommended by the MQU Design Guidelines Review Performance Standards [30].

Regarding noise levels, 52% of classrooms were within the recommended < 35 dBA limit. The high noise levels in classrooms were due to the air-conditioning systems. However, there was a trend of lower noise levels in classrooms that were more recently built. This may be due to technology developments in reducing the noise level of air-conditioning systems and closer adoption of the MQU Design Guidelines.

Regarding reverberation times, 65% of classrooms were within the 0.4–0.6 s limit. All classrooms had carpet; however, the majority of poor performing classrooms did not have acoustic ceiling tiles. There was not a clear trend of lower reverberation times for more recently built or refurbished classrooms. In fact, long reverberation times were found for classrooms refurbished in 2010, likely because the refurbishment did not include acoustic ceiling tiles. Reverberation time and floor area were not significantly correlated.

4.1 Towards an Acoustically Accessible Campus

The information collected in this study will go towards creating a more acoustically accessible campus. The traffic light colour-coded system used in Fig. 3 will be used to provide a communication friendliness rating of each classroom on the Macquarie University room information database. This database can be accessed by students and teachers, and there is also a direct link to them from the timetabling page. This will allow teachers to request which room they would prefer to teach in. It will also allow students to choose the best room for their communication needs when there are different options available for their tutorial classes.

The university is also looking into improving the worst performing classrooms. Acoustically treating classrooms can improve the acoustic environment and enhance students’ listening, learning, and well-being [32]. Reducing the noise levels and reverberation times of the classrooms to the recommended limits will help make them more accessible to both students and teachers with communication difficulties or hearing sensitivities.

4.2 Future Research

The findings of this study and the plans towards creating a more acoustically accessible campus give rise to future research opportunities. For example, it would be beneficial to conduct research that assesses whether the students and teachers use the communication friendliness information that will be provided on the university room information database and if so, whether they are more satisfied with their classroom environments as a result. It would also be worthwhile to do pre/post acoustic treatment studies with a class over a semester to better understand if making particular classroom modifications to the poor performing classrooms improves students’ and teachers’ listening, learning, and well-being. Additionally, it would be beneficial to assess how the acoustics of the classroom affects listening, learning, and well-being for those joining classes online given the current trend of remote learning.

5 Conclusions

This study assessed the current acoustic accessibility of an Australian university and found that 40% of classrooms met both the noise level and reverberation time limits. The university is currently planning how to use this information and make the campus more acoustically accessible so that all students and teachers can flourish. This is important not only for students who are attending the campus but also for those attending online given the current trend of audio recording classes and having remote participants.