Let’s find out together with acoustic expert Jean-Philippe Delhom, in this interview by 健住社 TREND

A Mysterious Stairway

The stairways in the showroom for a furniture company in Shanghai have a particular sound to them. As you walk up the stairs, your footsteps sound unusually loud, they seem to echo a little. If you speak, it feels as though everyone across multiple floors might be able to hear you, and yet someone standing right next to you may feel a little unclear as to what you said. Sound seems to be amplified, and distorted; louder, but somehow hollow.

As you walk into the reception area of the office, everything changes. Suddenly you can speak to the person standing next to you with a sense that all you’re saying is springing forth with absolute clarity. Your footsteps are barely audible, and there’s a sense that what you do say is remaining private between the two of you, with your voices not carrying across the large open space. You have privacy, and comfort.

What’s going on here?

The showroom has laid out its offices in this way for a reason. It is to demonstrate the difference between rooms that have undergone an acoustic treatment, and rooms that have not. If you were asked to stand in the stairway and picture giving a presentation, or holding a conversation, you would undoubtedly imagine an uncomfortable scenario. The way our voices travel affects how confidently we can conduct ourselves – if they are simultaneously hollowed out and amplified, it can make us feel self-conscious, worried that we are intruding.



This, simply put, is because the stairway has a high level of reverberation. We’ve spoken about reverberation before, but to recap, it is the degree to which sound persists in a space after its initial occurrence. Sound travels in waves, like ripples on a pond, and when it reaches surfaces, some of the force of those waves is absorbed, and some is reflected. Imagine interrupting a ripple on the surface of some water with a sheet of hard metal. The ripple would reflect back almost in its entirety. Now imagine placing a length of luffa sponge there instead. Some of the ripple would reflect back, but much would be absorbed by the porous, uneven surface of the luffa.

So it is with sound. Hard, flat surfaces reflect a large amount of the sound waves that hit them. When there are two or more surfaces of this kind close to one another, as there are in many rooms, sound waves bounce back and forth between them. When a room is made up of too many of these surfaces, the sound takes a noticeable length of time to die down. In audible terms, all sounds begin to have a long tail-end.


Try it out yourself

If you’re at home, go between the different rooms, and clap. You’ll notice that the very same clap can sound completely different in the kitchen than it does the bathroom, and different in the hallway as it does just outside your front door. If you have a long hallway or corridor and clap at one end, you may feel as though the sound is heard flowing more down the hallway, away from you. This is because of how the sound is bouncing. It is because of reverberation.

How do things sound in a room that’s had acoustic treatment?

The showroom aforementioned has undergone acoustic treatment. This means that certain sound-absorbing materials were selected and placed appropriately to achieve a comfortable acoustic balance. That is, they aimed to reduce reverberation to a degree where conversations would be comfortable and feel private enough, but not so much that the sound in the air felt dead.

The answer to the question above really depends on the purpose of the room. Acoustic treatments are adapted depending on the purpose of the space to which they’re applied. For example, in call centres, there are usually large open-plan office areas where employees take phone calls in close proximity to one another all day. The key objective of an acoustic treatment here would be to minimise the degree to which the sound from one call might interrupt another. It would require a fairly robust use of acoustic products, creating a space where sounds die out very quickly. That ‘tail-end’ mentioned above is shortened as much as possible.

Acoustic treatment for call center
Acoustic treatment for call center

Different industries, different treatments

In an auditorium used for giving presentations, a different type of acoustic treatment would be applied. The aim in this case would be to allow the sounds produced on-stage to travel easily and clearly across the audience, but to be absorbed behind and around them to maintain a high level of clarity. Meanwhile, sounds from the audience shuffling in their seats, getting up to use the bathroom, or whispering to one another, would need to be minimized. The room would therefore have gradations of sound-absorbing materials, to achieve these multiple effects.

Acoustic treatment for meeting room
Acoustic treatment for meeting room

Our Services

At Zenfeel we provide a comprehensive service when it comes to acoustic treatment. We often conduct consulting on sensible, space-appropriate acoustic design solutions. We have a whole range of acoustic products that seamlessly blend into any commercial environment. And we are experts at installing acoustic design products.

Sometimes our consultation and/or installation involves coming in before the construction phase of a planned space. This is the ideal point at which to start putting in place decent acoustic solutions, as the treatment can go hand-in-glove with existing construction plans.

Other times, it may involve a turnkey acoustic retrofit. This would first involve doing an acoustic study of the space, then creating a treatment design, installing purchased materials and finally following up with a performance check to guarantee results. While this may sound daunting at first, acoustic products are so flexible that usually a little bit of work goes a long way.

For the acoustic comfort of employees, a better environment for customers, and a sustainable way to maintain noise levels, acoustic treatments are an invaluable investment.