Mis à jour le 26 February 2019.
Few of us are aware that 70% of the sound that reaches our ears has first reflected off surrounding surfaces. Only 30% of the sound we hear arrives directly to our ears. The acoustics of any listening room are an important and even crucial factor, since reflections give rise to amplification and delay.
A source of inspiration: the movie theater
Have you ever wondered how acoustics are optimized in a movie theater? Despite the high volume level, the profusion of speakers and the large size of the screening rooms, the sound is not aggressive and does not cause unpleasant vibrations. In fact, quite the opposite is true, and there are several reasons for this. First of all, movie theaters benefit from extensive acoustic research in order to promote a harmonious distribution of the sound wave throughout the screening room. The basic idea is simple: reduce the 70% of sound waves that are reflected off the walls, floor and ceiling by minimizing opportunities for such reflections to occur. To this end, a movie theater presents a natural advantage: its surface is covered by many seats composed of foam and cloth, two materials with a high damping capacity. The floor itself is covered in carpet, which is another material with a high damping capacity. The ceiling is often tiered in order to capture and trap sound waves before they can be reflected. Lastly, the walls are sometimes covered with carpet or cloth, as is the case for new Dolby Atmos certified screening rooms.
In your home, the acoustic characteristics of your listening room are fundamentally different. Unlike a movie theater, which benefits from a high damping capacity, a living room naturally provides opportunities for sound to reflect. The presence of hard, smooth surfaces (glass, tile, wood flooring, plasterboard, concrete?) is a real problem for mids and highs, as these frequencies are prone to reflections.
To ensure optimal results, the floor, walls and ceiling should all be considered together. However, it isn’t a problem if you aren’t able to take all three into consideration, as increasing the damping capacities of a single wall can totally transform the acoustics of your listening room.
Improving acoustics: the floor
Ideally, a large carpet should be placed on the floor to eliminate undesirable reflections. Note that thicker carpets offer the best results. However, not everyone wants to install thick wall-to-wall carpeting in a living room, especially if it opens out onto the kitchen, as this would expose the carpet to heavy wear and tear.
When it comes to acoustics, the number one culprit is tiles, as their smooth and hard surface reflects the mids to which the human ear is very sensitive. If your living room has tile flooring, we highly recommend covering it with one or several thick carpets, especially between the speakers and the listening area. Installing a sprung floor composed of solid wood’and not fiberboard’will also greatly enhance the way sound is dispersed throughout the room.
If there are wooden floor joists in your listening room without any mineral wool or insulating foam filling in the gaps, the floorboards may act as a ?resonator. This is particularly problematic for lows and will affect the overall sound restitution. Adding cellulose wadding can solve this problem. Ultimately, wooden floor joists are still less problematic than tile flooring and waxed concrete.
If adding a carpet or solid wood sprung floor is not an option, you can reduce reverberations by ?breaking up? sound waves before they come into contact with the floor by installing a coffee table or decorative objects.
Rule of thumb: Adding furniture and decorative objects to your listening room will allow you to optimize the performance of your audio system.
Improving acoustics: the walls
Optimizing the acoustic qualities of a wall will provide immediate results. Often, furniture is placed close to a wall, or paintings and other decorative objects are hung from a wall. Full bookcases are very efficient sound traps. These are best placed behind the listener. The sound diffused by the speakers will then travel beyond the listener but not be reflected by a bare wall. Another solution is to install a thick curtain along the wall behind the listener.
Glass windows, like tile floors, generate a lot of reflections. You can consider installing a thick curtain in front of a window, and then focus your attention on the walls and ceiling.
Improving acoustics: the ceiling
A living room ceiling is most often flat and smooth. This makes it yet another enemy of good room acoustics. Acoustic panels may be installed to reduce a ceiling?s reflective potential by partially absorbing mids and highs at prime locations, including above the listener.
On the other hand, a smooth ceiling should be left as is in one kind of audio installation: those which include vertical Dolby Atmos / DTS:X speakers designed to project sound toward the ceiling and reflect it back down to the listener. Optimizing the acoustics of your ceiling is only necessary if you have a ?horizontal’ home theater installation (5.1, 7.1, etc.) or hi-fi installation.
If you enjoy home improvement projects, then creating a suspended ceiling, whether tiered or flat and injected with foam (polyurethane, for example) and perforated, will allow you to radically reduce reflections and even capture sound waves. A similar partition (plasterboard or wood) can be used for the wall behind the listener. This solution is adopted by some indoor swimming pool facilities as it captures sound waves reflected off aquatic surfaces.