Introduction to Acoustic Illusion
Welcome to the wonderful world of illusion. Welcome to the level where the eyes, ears and the rest of the senses part ways. But this time I won’t tell you about anything magical. It’s just some bits of physics and biology interacting. And all of this can happen from the comfort of your couch by using appropriate sound reflection and diffusion.
In this article we will explain in very simple terms how our body could translate a small room into a large music hall. This is of particular interest to those who want to enjoy music and often find themselves trapped in the dimensions of a small room that limits the scope of the music and does not allow it to spread beyond the walls that the eyes also face. How can we finally break the boundaries of a small room and unfold the dimensions of the music stage beyond any limitation? How can we see the opposite wall at a distance of three meters and at the same time have the music stage have endless depth like in the Concert Hall?
The Brain’s Acoustic Perception
Our brain translates space acoustically, with a precision that we cannot perceive. Our auditory system has capabilities that many precision instruments would envy. It is therefore very easy for our brain to receive the first reflections from the room where we listen to our music, and to calculate with great accuracy that the ceiling is two and a half meters or three and a half meters high, or that the side wall is very close to us.
So, our brain can very easily calculate that we are in a small room, and this is the trap that will not let our music spread beyond this dimension. Surely many people reading the article have a large space to enjoy their system and what I am describing may not concern them, but maybe it does? In any case, being able to break the physical dimension of our room, using sound diffusion, is desirable. This is what frees each recording and allows it to unfold to where the sound engineer intended.
Misleading the Perception of Space
But in the meantime. Since our brain calculates the reflections of our space to estimate physical space, what would happen if we tricked it and let it believe that the side wall is five meters from the listening position or that it doesn’t exist at all? There is a feasible way to do this. We can simply not let the natural first sound reflections of the room reach our ears.
Acoustic Management Techniques.
It’s so simple in theory. We just need to stop letting our brain believe it’s cramped in a room and take advantage of sound diffusion!!
But how does this work practically in a small room? Each first reflection, which would travel just a few meters from the speaker to our ear, will need to travel three times or more distance to reach us. Something like this would certainly correspond to the Megaron Hall, right? To achieve this we can use reflection and sound diffusion at the points where the first reflections are created by our speakers. For example, in a room five meters long, the sound emitted from the speakers at one end, to the listener at the other end (approximately 4 meters away), travels about five meters to arrive via reflection from the ceiling.
Creating a Sense of Depth and Height
By placing appropriate reflection on the ceiling to direct the sound back to the front wall and appropriate sound diffusion on the front wall so that the sound from the ceiling spreads throughout the space instead of ending up on our carpet, we will have managed to achieve a first reflection that reaches the listener after 7 to 15 meters. In practice, our brain is not even able to clarify what the limit of the ceiling is, nor of the front wall anymore!
Expanding the width of our scene
In the above way, we have managed to create an unlimited dimension of height and depth in a room with small finite dimensions. But what about the width of the stage? If we let the side walls send us a clear first reflection our room will remain “narrow”. So we need to eliminate this first reflection. Many of you will have already thought that an absorbent panel at the first reflection position on the side wall is the basic idea.
Limitations of Acoustic Absorption
But in the case of the acoustic panel, we will absorb the energy emitted to the side wall, and this energy will never return to our room. This takes the life out of the music, makes it dry, and limits the stereo image of our system between our speakers. If that’s enough for you, you don’t need to read any further. If some of you want the breadth of the music to be unlimited and continue to stretch out to your side until it hugs you from behind, you might find the rest interesting.
Alternative Approach: Direction of Energy
So instead of absorbing the energy coming from our speakers towards the side walls, we will direct it. With a combination of reflection panels and soft sound diffusion, which we place on the side walls, we cover as much area from the first side reflection of the speakers as we can. This is the holy grail for a stereo stage in a small space.
Directed Reflection and Timing
With the appropriate inclination, we direct this reflection, which would reach our ears directly (and create cancellations and a narrow room), to go to the back wall to our right and left respectively, without reaching our ears. I know it sounds a bit complicated but it’s worth it for better listening room acoustics! We’re not done yet though.
Our goal is for this energy that we sent to the back wall to reach our ears at the time we want, the time when the first reflection of the concert hall would arrive! And we are very close to achieving it. The back wall reflects the energy we sent from the side wall, back towards the front wall (by using a diffuser on the sides of the back wall we achieve a greater distribution of the reflection length) and from the front wall, finally the side reflection reaches our ears, neither more nor less, after 11-14 meters.
Sound Diffusion and the Effect of Space on Perception
This is really a huge difference for a room that is only 5 meters long. As you have noticed through this controlled sound diffusion we have led our brain into great confusion, as it can no longer clarify any boundaries in our room.
3D Acoustics & Reality
It sounds magical but it’s just natural. The music is heard coming from everywhere, with height and width. The depth is endless, and all this in a small room. All the endless efforts to improve our system with better equipment and better cables, finally find a place… and space!!!
In summary, it becomes clear that with the right approach, sound diffusion can transform even a small room into a listening space with a sense of unlimited dimensions. It is not magic, but about understanding how the brain perceives sound and applying the appropriate techniques. If you would like to discuss in more detail how you can achieve the “big picture” with sound diffusion in your own space and explore solutions that suit you, please do not hesitate to contact us.
