Home theater soundproofing: why, why and how
The plot is in full swing, and the hero of the movie entered into an unequal battle with an insidious enemy. Or a tense, eloquent silence reigned in the world of the tape ... And then from the next room you can hear the echo of someone else's conversation, a car is driving along the street or a dog starts barking boringly. And the charm of the film is destroyed, returning the viewer to the mundane.
Not a very pleasant feeling. Now it will take some time to get back to what is happening on the screen. Or you may not be able to plunge back into the magic of the film at all. To avoid such situations, you need to think carefully about isolating the room from external sounds - there is no boring reality for at least a couple of hours! And those around you will not be hindered by protection from your film - in terms of sounds, of course, so as not to toss and turn without sleep from side to side while a funny musical comedy is playing somewhere nearby.
Soundproofing and sound reduction
Before we start talking about soundproofing a home cinema, we need to clarify the terminology. Let's figure out how sound insulation differs from sound absorption.
- Sound insulation is the complete elimination or reduction to negligible levels of noise entering the room from the outside.
- Sound absorption allows you to leave the soundtrack of what is happening in the room within it.
To solve both issues, special materials are used and a special geometry of the room is being developed. The right combination of these two factors allows you to deal with several types of noise that can enter the room from the outside or inadvertently escape from it through unprotected walls:
- Airy - all sounds that are transmitted through the air - conversations, the noise of working equipment, the barking of a dog, and even the attack of combat tripods from Mars.
- Impact - knocks that occur when objects fall on the floor, which is the ceiling of the cinema, or when they hit the walls: the knocking of an ax (at least the famous scene from Kubrick's The Shining was played on the screen), jumping children and the notorious the stomp of cats. In the cinema itself, percussive sounds can be produced by subwoofers, and such noises are clearly distinguishable from the outside, even if the dialogue of the characters and the music does not break through.
- Structural is the noise that occurs during the operation of the engineering systems of the house: the hum of ventilation, the movement of the elevator along the mine.
- Acoustic - most often it is an echo that makes it difficult to understand what is happening on the screen.
The most pressing noisy problems for cinema audiences are the first two, as they are equally likely to have external and internal origins.
Of course, in any cinema hall special acoustic panels are used, fixed on the walls and capable of absorbing unwanted sounds, but you should not rely only on them. The area and construction of even the most expensive and high-quality models will not be enough to effectively solve the problem with excess noise.
Taking care of sound insulation and sound absorption
When building a home cinema, it is important to properly equip entrances and windows. The issue of soundproofing on these fronts is solved by installing multi-layer doors, vestibule doors or using a monolithic canvas.
High-quality double-glazed windows are installed in the windows, and for the duration of the session they are covered with a heavy dense fabric that will reflect and attenuate the sound. The same curtain can be provided for the doorway - it certainly won't be superfluous.
All interior details that can vibrate, creating rattling, must be well secured. Ventilation and heating pipes should be wrapped in acoustic materials - playing the flute of downspouts does not always harmonize with the director's intention.
It is better to immediately foresee that the ceiling and walls are not fastened together into a rigid single structure. If they are isolated from each other, it will be much easier to control the sound transmission of the room - there will be no weak points such as surface joints.
The main types of soundproofing in a home theater
The easiest thing to do is to adjust the sound insulation at the time of the construction of the building - that is, if we are talking about a completely new apartment without finishing or about the construction of a country house. In this case, it is enough to design the desired structure and bring it to life.
Wall soundproofing can be done in two ways
- Frame - before installing the sound-absorbing material, it is necessary to mount a special lathing made of aluminum, which is filled with mineral wool or other fibrous materials. From above, such a structure is usually covered with drywall. If there is a risk of vibrating parts when playing a movie or music - this is typical for large rooms - then the metal frame can be replaced with a wooden one.
This method has one big drawback - the construction is very massive. It takes a tangible part of the space from the room, which can be critical for small rooms
- Frameless - multi-layer panels glued from drywall and sound-absorbing materials are attached to the wall. They are fastened together like pieces of a puzzle, which prevents the formation of cracks where sound can leak. The structure is fixed through special vibration isolating units.
Ceiling soundproofing is usually solved with the installation of a false ceiling. But it must be borne in mind that a conventional filler like mineral wool may not be enough for high-quality sound absorption. It is better to replace it with special acoustic or noise-canceling panels. It is advisable to install vibration pads at the joints of the structure with the walls.
The floor can be made floating - placed on a special substrate and "untied" from the walls. Less seams mean less sound leakage.
Is the basement the ideal place?
The best point for setting up a home cinema on a home map is usually the basement. This room is naturally isolated from everyone else in the house, so it seems like all that remains is to refine the details and enjoy the good sound without disturbing the other inhabitants of the house.
However, things are not so simple. Concrete walls become an excellent resonator for low frequencies - they are hardly absorbed by such material, but are reflected back into the room. And this unpleasant property can be supplemented by one more effect - the low frequencies not only return, but also continue to sound for some time, gradually fading away.
There are not very many materials that are able to effectively remove resonant low frequencies, and they are distinguished by a high price. But if you want to equip a home theater in the basement of a house, you can choose sound insulation that quite successfully removes this drawback.
For troubleshooting, you can use complex sound-absorbing structures, reminiscent of a layer cake, in which reflective and absorbent materials alternate. Viscous ones vibrate, converting the sound wave into heat, while porous ones absorb and drown it out.
Another way to get rid of low frequencies is wall cladding with double sheets of gypsum fiber board. The space between them is filled with mineral wool or any other fibrous absorbent material.
Concrete walls can add another surprise, the SpeakerBoundaryInterferenceResponse (SBIR), where acoustic reflections from a nearby wall clash with direct sound, creating a cacophony in the audience's ears. You can remove this effect if you mount the speaker diffusers in the plane of the wall. This is what they do in the best cinemas, and nothing prevents you from taking advantage of their experience when setting up a home cinema.
Let us add that a specialist should be involved in the development of a special decorative and functional design of the cinema. He should be involved at the stage of project development. It is enough for the master to provide a diagram of the future hall and a list of equipment that will be installed in it. Based on this data, he will be able to select the right materials.