Acoustics In Education: Can Acoustic Design In Lecture Theatres Affect Speech Intelligibility?
University is a life defining period of time for most students. The subjects they study and the grades they come out with become influencers on the options available to them after graduation.
Learning in environments that are acoustically designed to maximise their potential outcome is a rite that students should automatically hold at university. Speech intelligibility in lecture halls can play a huge part in this.
Read on to find out more…
Learning In A Lecture Theatre
For most students, lessons will take place in lecture theatres. Lecture theatres, school halls and other large spaces are used for teaching, assemblies and meetings. These spaces allow module leaders to teach hundreds of students at once, eliminating the need to teach the same class several times a week because of space limitations.
Science Daily writes that “understanding how students interact and learn within the lecture theatre environment is central to successful learning”. In large spaces like lecture theatres and school halls, a common problem is high reverberation times which affect speech intelligibility because noise levels are naturally higher.
Student’s will place themselves in a lecture theatre depending on individual needs. Often this is with friends, or in a place there they are out of the lecture’s eyeline to avoid being asked questions. This isn’t always the case however, other student’s may purposely sit near the front to contribute or because of specific learning needs.
For lecturers, this means using the space to project their voices in a clear, understandable way that carries to the whole auditorium. If these spaces are improperly designed however, some student’s may not be able to hear the lecture properly, which could impact their learning experience. Speech intelligibility is a large part of this.
If a space is not designed with speech intelligibility in mind, the reverberation time for sound will be higher, meaning that students will have a more difficult time hearing the class because the sound of the lectures voice will echo more, rendering it less understandable.
For lecturer’s, poor speech intelligibility can also be an issue, as the sounds created by students talking, taping pens or shuffling in their seats will take longer to fade away, making it a distraction to their lesson.
Universities And Design Regulations
Universities are exempt from The Building Regulation E4, meaning that they aren’t forced to comply to the same standards set out for schools and nurseries.
The BB93 Design Regulation, states that: “many of the acoustic specifications [from the regulation] are desirable and can be used as a guide to the design of these buildings”, giving designers the option to optimise higher education spaces for the maximum comfort of the students.
Part of that comfort comes from the ability to understand the lecturer, and to be able to communicate questions to them clearly to reinforce learning.
Exemption from The Building Regulation E4, and BB93 Design guides, mean that lecture theatres can be designed with little to no consideration for how sound will carry. However, to ensure that the space has maximised usability, close consideration is important. Sound must transfer from the lecturer to the student as be as strong as possible no matter where the students are seated.
Sound weakens as it travels in line with the inverse square law. This law states that “the intensity is reduced by a factor of four and the sound level falls by 6 dB when the speaker to receiver distance is doubled”.
This is why distances between students and teachers should be kept short wherever possible with no obstructions between them. Since sound that is heard by the student 50 milliseconds after the initial noise is made is likely to be disturbing, it’s vital to avoid obstacles for the sound where ever possible.
In large spaces, such as school halls and lecture theatres, this can be managed by including acoustically absorbent materials on the rear walls to absorb the sound where late reflections are likely to take place. Lecture theatres can also include control room windows to move reflections of sound away so that students are free to learn.
Sound that’s focused by domes or barrel vaults can cause echoes and reflections as seen in the image above [ref: Acoustics of Schools – a design guide November 2015]. This is particularly true is they are above a hard floor, as are often found in lecture rooms and school halls. Flutter echoes may develop in these spaces which can interrupt the speakers and students which can be detrimental to learning.
An acoustically well-designed room will maximise the levels of speech intelligibility even if there are large numbers of students in the room. However, it may be necessary to include speech reinforcement systems to improve the sound in certain cases, such as when quieter speakers are carrying out classes or during student presentations.
These systems improve the volume of direct sound so that it can be easily heard by all, especially those at the back without losing the natural flow of the lecturer’s speech. This maximises speech intelligibility.
Loudspeakers can be distributed in the walls and ceiling at high levels such as along walls and on columns. In large halls these speakers should have natural time delay considered before they are installed so that distant receivers are factored into the layout. These may require electronic compensation to adjust the output to be correct when sound is made.
Specialist acoustic consultants sound be consulted when designing sound reinforcement systems because of the nature of the field. If the systems are incorrect for the space, there is a risk that speech intelligibility will be hindered rather than helped.
How Can Acoustic Consultants Help?
Prism Acoustics offer acoustic consultancy to architects, specifiers and designers to ensure that spaces such as lecture halls are designed to maximise speech intelligibility and improve the quality of a space for staff and students alike.
Using our own 3D Acoustic modelling software, we can create noise maps to show how a lecture theatre will sound before construction work has begun. This allows for a smooth process as the space is constructed or refurbished to ensure student’s will be able to hear everything exactly how it should be.
Having acoustic consultants working alongside the project will ensure that speech intelligibility in a space is maximised and prevent students and staff losing out on key learning opportunities in lectures thanks to the creation of excellent acoustic design.
About Prism Acoustics
Prism Acoustics are leading acoustic consultants based in Birmingham in the West Midlands.
Prism work alongside architects, designers and developers, offering acoustic consultancy on a range of projects in the following sectors:
- Sound monitoring and acoustic modelling for live events.
Prism are currently developing the next generation of acoustic prediction software, using virtual reality to demonstrate how the sound will carry before development work has even started! We can carry out environmental noise surveys and will work alongside you to ensure that your acoustic needs are met to the highest standard.