Here is a simple formula to gauge your design on its acoustics

** Here is a simple formula to gauge your design on its acoustics **

In my recent posts, I discussed how we should create memorable moments to shape our perception of spaces. But I also told you that while these moments are essential, it's equally important to ensure that the basic comfort variables are solved.

Let’s continue with the reverberation theme of the last post as acoustics can be a daunting subject for designers. And yes, it is an area with many factors playing a role which I don’t want to disregard here. Still, there are some simple guidelines that can help you design with it.

Back in the 19th century, Wallace Clement Sabine, who is seen as the father of architectural acoustics, studied the acoustics of concert and lecture halls. He formulated a very practical formula that you can use to gauge the reverberation time of a space:

👉 RT=0.16×V/A (looks pretty simple right? No logarithms to be found as you would usually see in calculations in acoustics... which btw is also nothing to be afraid of…)

Where:
● RT is the reverberation time in seconds.
● V is the volume of the room in cubic meters.
● A is the area of a perfect absorber in square meters. This is the total area of the absorbing surfaces in the room multiplied by their absorption coefficients.

In simpler terms, the formula illustrates that the reverberation time is proportional to the room's volume and inversely proportional to the amount of sound-absorbing material present.

Let's look at an example: A meeting room of 5 x 5 x 2.8m.
If you aim for a reverberation time of 0.5s you can use the formula of Sabine to calculate the area of acoustic absorption needed:

0.5s = 0.16 x (5x5x2.8)/A => A=22.4m2
Hence, you would need an area of about 22.4m2 of total absorption.

The easy way out (and probably the cheapest) would be an acoustic ceiling with an absorption coefficient of 0.9 leading to 5x5 x 0.9 = 22.5m2, pretty much exactly the amount we need. And now you know why this is so often proposed.

Now think about a different solution for a design with ceiling islands that cover only 70% of the ceiling... How would you deal with the rest of the room to get to the targeted reverberation time?
How much could the floor realistically contribute? are there walls available or are they all from glass? What kind of furniture or other elements do you have to play with…?

While the science of acoustics has evolved since Sabine's time, this simple formula is still a great tool for early-stage design decisions.
Will you give it a try?

What else would you want to know about acoustics in the design of healthy buildings? Let me know in the comments 👇

#healthybuildings #SustainableDesign