How to design a better-sounding audio system in the reverberant room - so our ear can hear word by word?
After reading this article you will understand:
Architectural Acoustics and Audio System is one close system
A common misconception between Sabine Reverberation Time and Reverberant Sound Level
How to design a better-sounding audio system in a reverberant room, without redesign architectural acoustic.
Assume we sit in the back of the hall as shown in the picture above, and we barely hear the spoken word by word clearly because the reverberant sound level is bigger than the direct sound level. As we can see on the bar chart above if we sit at the front row the direct sound level is bigger than the reverberant sound level, in the middle part we might hear the balance of direct and reverberant sound.
Usually, in this situation, we always think it happens due to the longer Sabine Reverberation Time of the room, or the loudspeakers is too far so we need to add more loudspeakers at the back of the hall so the people can hear the speech more clearly.
This statement is not 100% correct.
Let’s analyze Hopkins and Stryker Equation as follow:
From the two equation above we know that there is a unbroken correlation between Architectural Acoustic Parameter such as Absorptoon Modifier (Ma), Total Acoustic Absorption in the room (Sa) and the Audio System Parameter such as Loudspeaker Directivity Index (DI), Number of Loudspeaker (N) and so on.
What should you know about designing a intelligibility sound system and room?
To increase speech intelligibility our goal is to make the direct sound level ratio is bigger than the reverberant level. As from the equation above, there are four things we have to be aware of if we want to increase the direct level while lowering the reverberant level.
(1) From the Direct Level Equation below we understand that if we want to increase the direct level, we can increase loudspeaker output level (Lw) and/or the Directivity Index (DI).
(2) But if we look at both equation Ld (direct level) and Lr (reverberant level) increasing loudspeaker output level (LW) will increase both LD and LR.
(3) From the Reverberant Level (Lr) equation, we also understand that quantity of loudspeakers (N) will affect the reverberant sound level (Lr). If we increase the number of loudspeakers (N) it means we increase the reverberant sound level (Lr).
(4) Directivity Index (DI) of Loudspeakers is accounted for Absortion Modifier (Ma) term in the LR formula. If the DI confines the energy to a specific area with a very reflective and reverberant room (RT60), then the Reverberant Level (LR) is reduced because the lower surface area that reflecting the direct sound of the loudspeakers.
To prove point number 2 above we make two (2) sound auralization in the hall comparing six (6) undelayed loudspeakers configuration versus four (4) delayed loudspeakers configuration as below.
Auralization & Animation Electro-Acoustic Software Modeling - 6 Undelayed Distributed Loudspeakers
Auralization & Animation Electro-Acoustic Software Modeling - 4 Delayed Distributed Loudspeakers
From the two auralization above we can conclude beside the importance of architectural acoustic design, to increase speech intelligibility we have to design simultaneously architectural acoustic and loudspeakers configuration as well as microphone position.
If you are facing a problem with lower speech intelligibility in your room, which makes your audience struggling to understand every word said.
If you have tried to solve the problem by buying better loudspeakers and it does not solve the problem.
If you want to improve speech intelligibility so your audience can hear better word by word spoken.
Our proven Architectural-Acoustic-Audio-System design methodology will help you get rid of this problem. We have a proven track record of helping companies solve their acoustical problems while saving money and time. Hit the Contact Us button below to discuss how we can help you.
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