Home Theater Design - Home Theater Room Design: Room Acoustics Basics
Updated: September 6, 201

Home Theater Room Design Basics

Home Theater Room Acoustics and Sound-proofing

No basic home theater room design is complete without appropriate consideration to the acoustic performance of your entertainment space, whether that being a dedicated home theater room or a shared space in the house.

Unfortunately, few realize that the acoustic performance of a room is very much dependent on the shape, size, and layout of the room - a fact often overlooked by many to the detriment of an enjoyable home theater experience.

The truth is that when it comes to home theater room design, the room characteristics affect just about every aspect of your home theater experience, from picture quality and acoustics, to overall comfort and movie enjoyment.

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Acoustics and Soundproofing in Home Theater Room Design

The acoustical performance of your home theater room represents an important element for a clear and optimal home theater sound.

No matter how good your home theater sound system is, if the environment within which it is operating is not geared towards good quality sound, it will sound terrible.

This in itself is dependent on the nature, as well as on the overall area of the different surfaces within your home theater room.

In particular, the room's construction, furnishings, widows, and wall surfaces, all have a massive impact on the acoustic performance of your home theater.

Unfortunately, many would-be home theater rooms are less than ideal for the purpose from an acoustics perspective.

Sound reflections from the different surfaces, and refractions as sound travels through different materials, all lead to serious sound distortions. Furthermore, there is also the issue of noise transmission both from within the home theater as well as from outside. One has to look at ways on how to stop sound crossing the room boundary, more specifically, to soundproof the home theater room.

It is not the scope of this home theater room design article to go into the details of soundproofing. Soundproofing is best carried out by a professional as if it done wrongly, it can make things sound worst ...and that would surely turn out to be an extremely expensive mistake!

Yet, there are a few basics about soundproofing which if followed carefully by the DIY enthusiast at the early stages of any home theater room design, may help avoid wasting thousands of dollars in creating a 'room-within-a-room', which is in essence, the basis behind sound isolation and sound control techniques.

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Reflective Surfaces and Noise Absorption

On one extreme, one finds 'hard' reflective surfaces that leads to a harsh echo-filled sound; the other extreme are those 'soft' very absorptive type surfaces that lead to a dull lifeless sound.

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A room with all hard surfaces such as wooden or ceramic tile flooring, gypsum partitioning and concrete ceilings, etc., represents the ideal environment for a high level of sound reflections leading to echo and extremely poor sound quality.

This echo or reverberation level increases with an increase in the sound level. The solution is to introduce an adequate amount of soft furnishings to absorb some of this echo.

The other extreme is a room with all soft furnishings such as fitted carpets and wall to wall curtains - leading to an acoustically 'dull lifeless' room. 

For optimum results, your home theater room design effort should aim at striking a balance between these two types of acoustic surfaces. 

Sound Absorption Control

Controlling sound absorption implies changing the characteristic of the sound within your home theater room. Stop it from echoing by controlling the reverberation. Stop the noise reflections.

As already indicated, for this type of sound control, you will use carpets, upholstered furniture, acoustical ceiling tiles, soundboard, etc.

However, there is even more to just striking a balance when it comes to home theater room design. The position of these absorptive and reflective surfaces with respect to your speaker placement plays a critical role towards achieving a pleasing overall acoustical home theater sound.

The following are just a few practical guidelines to take into account during your home theater room design process; these should prove useful to help improve the acoustical room performance:

1] Carpeting is essential especially between the front speakers and the listener to catch the first reflective sound waves.

2] The use of acoustical wall paneling or curtains close to the front speakers will also help in this respect. However, do not fall into the temptation of painting your acoustic paneling - this will only reduce their effectiveness.

3] Other soft furnishings such as sofas and cushions will also contribute to absorb some of the echo.

4] On the other hand, the ceiling should preferably be an all-hard surface so as to carry the sound from front to back while helping to further diffuse the surround within the room.

As a rule of thumb, your home theater room design should aim at having some 50% of the total room surface area - wall, ceiling, and floor area, absorptive. Most of these absorptive surfaces should be within the front part of your home theater room.

The rear part of your room should contain surfaces that are more reflective; this will help diffuse better the surround sound within the room from your rear speakers.

So... How can you strike this much-desired balance in your home theater room design?

Experimentation is the name of the game! One needs to experiment with the positioning of any soft furnishings around the room - an essential approach for an effective home theater room design.

The end result however is more a question of personal preference.

Soundproofing and Noise Transmission

Directly related to a home theater room acoustic performance is noise transmission between adjacent rooms in your house. Neither will you want to disturb others with your home theater sound, nor to be disturbed during a good movie with undesirable noise from outside.

In other words, you may have to create a 'room-within-a-room' to isolate the inside walls, ceiling and floor, as much as possible from the rest of the house. In this manner, you will be able to control the impact of the sound system on the room itself as well as stop the transmission of sound from both within as well as from outside.

While soundproofing a room can turn out to be expensive and a huge project in itself that is best done by a professional, yet it is possible for the DIY to soundproof a room without spending big money. The reason is that when it comes to the transmission of sound between adjacent rooms, the worst contributors are windows and doors rather than walls, ceiling and flooring.

In other words, your first approach in your home theater room design effort should be to soundproof the windows and doors of your room before proceeding with the much bigger investment required to soundproof the rest of the room. If you do not proceed in this direction, you may end up wasting thousands of dollars in unnecessary soundproofing.

At this point, it is important to realize that noise absorption is different from noise reduction, and therefore what holds good for one, would have very little impact — if any — on the other. As indicated earlier on, noise absorption is used to control the quality of sound within a room; on the other hand, noise reduction techniques are used to control the flow of sound energy from one room to another.

Thus, while the use of insulating material between double drywall panels can effectively help to stop the noise from crossing the room boundary, it would not help to control the reverberation level of the sound within the room unless the outside surface of the drywall panels is treated with the appropriate material, like acoustic fabrics or specially formulated acoustic foam panels.

When it comes to soundproofing a home theater room, there are three things that can help you stop noise from crossing the room boundary:

1] Space: Increasing space will help reduce noise.

2] Mass: The heavier the material, the more sound it will stop.

3] Dampening: This represents the absorption of energy as sound travels through a medium to help the vibrations die away. Thus, making the noise travel through heavy soft materials will help to dampen the noise better.

Reducing Noise

You can adopt various approaches to reduce noise. These have to be taken care of at an early stage of your home theater room design as these often imply substantial re-construction effort.

Noise reduction always relies on the use of mass and space to maximize the dampening of sound as it travels through the room structure.

As indicated earlier on, your effort should first focus on the openings in your room like doors, windows, etc. To this effect, you have to ensure that any doors and windows within your room should have a solid core structure with a tight rubber seal to reduce noise transmission. Increasing the space in between your double-glazed windows should help reduce noise.

Only once you have completed this step that you should consider additional soundproofing of your walls, ceiling and flooring if your first attempt is not fully effective in reducing noise.

When it comes to soundproofing of walls, the basic requirement is to avoid studs of two adjacent walls from touching each other in order to cut the primary means for sound to travel between rooms.

Usually, a second extra layer of drywall will further enhance the noise reduction effect. This adds more mass that will help dampen the noise vibration when traveling through the structure.

To dampen further the sound, apply some appropriate insulation inside the wall cavity; adding soundproofing material between the studs and the drywall will further block sound vibration.

The use of special materials like 'Z-shaped' resilient steel channels to use inside drywalls and ceiling can help reduce large noise vibrations. Specialty Vinyl and other noise stopping materials like lead lined drywall all rely on the use of mass to dampen the sound energy, and thus to stop noise from crossing a structure.

For the technically minded, your aim should be to increase the 'Sound Transmission Coefficient', also referred to as Sound Transmission Class (STC) to around 55 or higher. This represents the ratio of the sound energy for a given frequency range (typically 16 standard frequencies spread between 125Hz and 4000Hz), transmitted through a surface to that incident on it.

This high level of STC is required as sound energy in the home theater may easily reach and even exceed 100dB during loud passages of music and movie sound effects. With an STC rating close to 55, such loud noise levels would only be faintly heard from an adjacent room.

Achieving an STC of 55 typically requires the use of double layer of 1/2″ drywall on each side, on staggered wood stud wall, with batt insulation in wall.

Note however that STC does not take into account the low energy sound transfer; the latter is in effect the main reason behind most sound isolation complaints.

On the other hand, the 'Noise Reduction Coefficient' or NRC, is a single-number index for rating how acoustically absorptive a particular material is. It is simply the average of the mid-frequency sound absorption coefficients (250, 500, 1000 and 2000 Hz). NRC gives no information as to how absorptive a material is in the low and high frequencies.

Room Shape and Acoustic Performance

Directly related to your home theater room acoustic performance is the shape of your room. The room shape plays an important role in any home theater room design in that it affects the sound quality in the room.

Ideally, the dimensions should be such that the room width, height, and length are not divisible by a common denominator. For example, a room that is square is not ideal for home theater use as this may lead to undesirable acoustic performance which will be more difficult to control.

Similarly, a rectangular room where the length is twice the room width is also not suitable.

If your room is inadequately proportioned, do not move to the next phases of your home theater room design without first attempting to modify the room dimensions accordingly. Possible solutions here include the use of drywall partitioning - e.g. by introducing a small projection booth at the rear of your home theater room, or a fitted wall-unit that you can use to house your big screen display and the front speakers, etc.

Effort spent at this stage of your home theater room design will surely pay off later during your movie viewing and music listening.

More 'FREE' information on
Soundproofing Your Home Theater Room

Additional information is also available in the following 'free-to-download' soundproofing manuals published by Quiet Solution Inc:

- Soundproofing Home Theaters and Media Rooms

- Making Walls Quiet

Equally interesting is the Acoustical Wall Insulation Design guide published by Owens Corning

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 Article Content

Issues discussed in this home theater guide:

Blue bullet  Acoustics and Soundproofing in the home theater

Blue bullet  Reflective Surfaces and Noise Absorption: Sound absorption control

Blue bullet  Soundproofing and Noise Transmission: Noise reduction techniques

Blue bullet  Ideal Room Shape for the best acoustic performance

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