Acoustic Panels For Sound Absorption
If you're like millions of people, you probably enjoy watching movies in the comfort of your own home with surround sound. Home theater systems can be expensive, and many people want to avoid the high cost of a full-blown home theater system. So many people turn to sound absorbing acoustic panels to improve the movie watching experience.
A common question that many people ask is how many acoustic panels do they need? The answer is that it depends. You can add as many acoustic panels as you need to meet the requirements of your specific theater room. Generally speaking, more panels are better, but sometimes too many panels can create a bit of echo in the room. Therefore, you should aim for the right balance of sound absorption and acoustical dampening. Your goal is to create the optimal home theater environment without an echo at all. Achieving this balance is usually best when your acoustic panels are properly positioned.
Thickness of Sound Absorption Panels
The thickness of sound absorption panels is a matter of consideration in most cases, especially if you intend to purchase the panels for domestic use. As a matter of fact, it is a common mistake not to pay adequate attention to the thickness of the sound absorption panels. However, this is one mistake that needs to be prevented since the thickness determines the level of quality of sound absorption that particular panel or group of panels is going to provide. In order to make a wise purchase, you should be aware of the thickness of sound absorption panels. This is because a thicker sound absorption panel is going to make a more significant impact on attenuating the home theater loudness as compared to a thiner one.
The thicknesses of sound absorption panels that are available in the market today vary from 1" thickness (for most general applications) to 4" thickness (for high-level applications). However, the 5" thickness panels are not as common as the others. In order to understand whether a particular sound absorption panel is suitable for the home theater installation or not, you need to determine the attenuation level that you are going to need.
The recommended thickness for home theater installation is 4" sound absorption panel. However, if a 5" sound absorption panel is available in expandable format, you can buy 3 5" panels and combine them to get 4" thickness for the sound absorption.
Thickness of Bass Traps
Designing a acoustic treatment plan requires analyzing the deficiencies of the room and addressing them. The key goal is to ensure that the sound falls off evenly over distance as well as over frequency.
The thickness of an acoustic panel or bass trap does not solely determine how well it can handle bass frequencies. These limitations are due to other issues like the type of membrane and the density of the fiberglass or rock wool that is used in the panel.
If you are using an acoustic panel with a rigid surface, it will be more effective in controlling higher frequencies, but will be less effective in controlling the fundamental frequencies compared to a bass trap that has a very soft diaphragm attached to it.
Based on this, while thick panels might be effective in controlling mid-range frequencies, they might not be the best choice to use in large rooms. In most cases, a thinner bass trap will be much more effective.
The thickness of the acoustic panels and bass traps being used are also more of a function of the speaker or studio involved. Some music styles may be heavy on bass, so acoustic panels need to be in panels that are much thicker. Using thicker acoustic panels will simply decrease the cost of the project as costs will increase with the thickness.
Reflection Points In Your Room
The experts at Waves recommend hanging at least one acoustic panel at every reflection point in your room. You can identify reflection points in your room by looking for spots where the walls, floor, and ceiling are parallel to one another.
Should you hang them lower than the height of the reflection points? No, hanging acoustic panels lower than the reflection points will not decrease reflections.
However, unless your room is extremely large, you will probably not be able to hang panels in every single reflection point in your room. In a small room, you can gather most of the reflection points by hanging acoustic panels on the wall that is parallel to the ceiling and floor.
You will have to decide for yourself how many acoustic panels you need based on your room size. Another decision you will have to make is whether to hang multiple acoustic panels in the same reflection point or hang multiple reflection points.
Some people may want to have several panels along the same wall. However, you must keep in mind that the more panels you hang in one reflection point, the lower the frequency at which sound will be absorbed. In other words, your room will look a bit messier, but the bass and midrange frequencies will be absorbed better and reflected less.
How To Find The Reflection Points
This may sound difficult. However, it’s actually an easy technique. The easiest place to find the reflection points in a room is in the corners.
The further you move away from the corner, the fewer reflections you’ll find. There are probably several reflection points in each of the corners, but most of them will be so faint that they won’t be audible.
Other common reflection points include windows, doors, and walls. Also, keep in mind that a large panel can have the same effect as multiple smaller ones.
That’s why John recommends obtaining acoustic absorption that’s calculated by total surface area rather than number of panels. In other words, consider your room’s dimensions and ceiling height, and then add up the surface area of the panels you would like to purchase.
What About The Subwoofer?
If you’re in the market for acoustic panels, the first question you most likely have is “how many acoustic panels do I need?” If you’re a first time home theater owner, this question might even seem daunting.
The good news is that your acoustic panel requirements are dictated by one simple factor – what area of your room do you want to control noise in. The first thing you’ll need to do is measure your room (it’s easy and cheap to use a tape measure). Next, take a look at the total room surface area (including the walls and the ceiling). This is what you should use when ordering your panels, whether you’re ordering from us or another vendor. You’ll also notice that when this factor is expressed as a ratio of the room’s total surface area, it turns out to be around 2% at low frequencies. To get the best results, you should use this factor when comparing acoustic panels to find a vendor that has the most coverage per square foot (or meter).
How Many Acoustic Panels Do You Actually Need?
Ceiling-mounted acoustic panels are very popular in home theaters. Manufacturers often claim that they treat the entire room, making it appear to be a perfect acoustic environment. However, what many people don’t realize is that you need a lot of panels (or a very large surface area of one panel) to make a significant impact on your room’s overall acoustics. As countless reviews confirm, front or rear wall-mounted panels only treat the area directly behind them, but you need to have many more to treat the rest of the room effectively.
That said, let’s first understand what it takes to treat a room via acoustic panels and then build a simple formula to find out the number of acoustic panels you need.
Priority 1 – First Reflection Points
Priority one on the path to perfect home theater acoustic treatment is to control the first reflections of the sound field, and the best way to do that is to place absorptive panels directly on the walls at the first reflection points.
Reflection points are locations inside a room where a sound wave can be reflected off a surface and bounce back onto another surface. In a typical movie theater, the front walls and the screen are the surfaces that receive these reflected waves.
If you can control the reflections coming off of the front wall, you will bring clarity to the dialogue in the movie. If you are watching tv and have the volume turned up, you can hear everything in the scene. When an actor laughs, you can feel the boom in the speakers. If the audio was not mixed properly, you may hear echoes in the room, and this is referred to as reverberation. This is where a room’s poor acoustics start hurting the listening experience.
When the first reflection is absorbed by an acoustic panel on the wall, the sound waves become too weak to be heard so they no longer bother the viewer. This can be done by placing acoustic foam panels on the walls at these reflection points.
Priority 2 – Bass Traps In Front Corners
Bass typically reverberates on walls. It may have come from a distinct direction or it may have spread across the room. You can try to adjust the tone and level of the bass by adding or subtracting bass traps in specific places.
The most effective way to reduce the magnitude of reverb is to add bass traps in the ‘hot spots’ you have identified. In the image above, corners are indicated by red rectangles.
Priority 3 – Bass Traps In Rear Corners
Why are the rear corners so important to treat? The rear corners have significantly more bass buildup than the front because of multiple factors.
The rear corners receive some audio signals directly from the rear wall and also from signal reflections from the side walls and floor. The mid to long-bass wavelengths are long and therefore interact with the rear wall more directly. In addition, the rear corners are not as influenced by side wall or ceiling reflections because the rear walls are generally parallel with the side walls.
As you add more acoustic panels to the rear corners and the side walls, the sound becomes tighter, more controlled, cleaner, and more natural. The bass in the rear corners is still audible in the front but is not overpowering or distracting.
Priority 4 – Reflection Points On The Front And Back Wall
Priority 4 reflection points will be your first set of acoustic panels, and they are equally as important as the others. These four points on the front and back wall of your room will eliminate a majority of the frequency-related problems in your theater room.
Starting with the front wall, your priority 4 locations are the corners at the front of the room. People generally don’t sit at the corner of a front wall, and they can be skipped in some rooms. But, they can be very effective at eliminating low frequency build up in rooms with poor first reflection points.
Next, you’ll want to position acoustic foam panels on the remaining two side walls of the front stage. These are the walls created by your first reflection points. They will act as the line between reflection and absorption, and you’ll need to use these to help eliminate enough buildup and control reflections so you don’t have to deal with a terrible first reflection point at the front of the room.
The front stage will be your picture frame and it’s important to control and eliminate ambient sound from it.
Priority 5 – Reflection Points On The Floor
The low frequency wavelength is generally about 16ft (5m) long. This means that the sound is reflected off the floor and into your ears. Most of the sound will be absorbed through surface reflection off the floor, but the bass will continue to bounce around.
Unfortunately, you cannot stop these reflections with conventional acoustic wall treatments. Quite often these bass points are on the floor underneath home theater seating.
This why the placement and the number of acoustic panels on the floor is so critical to preventing excessive bass build up.
For more information on how to use acoustic panels to create the perfect acoustic environment for your home theater, visit our Home Theater Resources website.
Priority 6 – Reflection Points On The Ceiling
The home theater should have one reflection point spot for every home theater seat. You can use this as your guideline. This means that if you have 6 or more seats, you should have 6 reflection points. If you have a theater seat with more than one person, count both people as a requirement for having a reflection point. For example, a two-person seat requires two reflection points.
The ceiling of your home theater room is especially important as you will want to reflect sound from the surround speakers. In general, the more reflection points you have the better your listening experience will be. The reflection points are a huge part of how you shape the listening experience. The trickiest part of the home theater is acoustically treating the ceiling. You will probably want to use hanging acoustic panels as this is the best and fastest way to treat the ceiling.
Priority 7 – Go Crazy With Bass Traps
If you want to go bat crap crazy with your bass traps and acoustic panels … buy 12. If you’re looking to really clean up your lows; buy 10 or more.
Use the lowest note frequencies that are objectionable in your room, note it, then add 10 Hz. If the frequency is still objectionable buy some bass traps and place them to fix that problem.
The more bass absorption you have the better. But remember, expensive is not always what is needed, just make sure it is dense enough to clean up the problem frequency range you are trying to fix. Adding 8 quality acoustic panels (dense) will make a much bigger difference than adding 1 or 2 cheap and small panels.
The Number of Acoustic Panels That I Would Recommend
Different types of acoustic panels, their purpose and their placement are primary factors that come into play when you’re trying to balance sound quality and the acoustic treatment of a room.
The number of panels you’ll need will depend on the size of the room, how much control you want over sound reflections, and the room’s potential for bass buildup.
You should start by hanging the highest quality panels that you can reasonably afford, then fill in the gaps with the other types of panels. This approach takes into account a combination of factors, including the average daily usage of the listening room. Acoustic panels are like curtains. Ideally, they cover the length and width of the room and prevent sound reflections from entering the room off the walls and ceiling.
This approach can easily rack up a big bill, but there are other factors to consider in terms of application and common sense. If the room is rarely used, then the panels shouldn’t be either. It’s also common to find that there is a different type of acoustic panel for every region of the room. This clearly indicates that panels are used as a sound treatment technique, not as a design component.
I’d break it down this way:
Living Room: 4-6 panels
Theater Room: 8-10 panels
Some Handy Tips
Acoustic panels are important for a home theater system. The room in which you decide to mount them is your "home theater room." While designing, constructing, and planning your theater and sound system, you must remember one thing: the acoustic panels are a critical part.
They help to control sound, prevent reverberations, and add depth to your experience through all the speakers in the system. It is a good idea to plan your sound system as part of an overall home theater system. Get the subwoofer or surround sound system working together with the correct amplifier and receiver. They will require the right acoustic treatment to match the speakers in order to make the system the best it can be.
The ideal acoustic panels for you will depend on how the room is, what your preferences are, and what you really want to listen to. If you are setting this up in your home theater, you are likely using the speakers you have as they are. You may not wish to buy more expensive speakers. In that case, avoid any piece that might interfere with other speakers, like the left and right rear channels.
Choose a size that will satisfy your space. Most make generous panels for a 12 x 12 or 8 x 9 or 10 x 10-ft space. You might find many other panels between 6 x 6 and 12 x 12 to cover your needs. Their panels are also known, in that they provide reflection control.
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One of the most obvious uses for acoustic panels is to improve the acoustics in a home theater or a movie room. Whether you are shopping for the perfect set of acoustic panels or planning to build your own, the question of how many acoustical panels you need to buy or make comes up frequently.
The type of acoustic panels you purchase and place in your home theater will be one of the most important components when it comes to sound quality. The number of acoustic panels you need depends on absorption and reflection. Off-the-shelf acoustic panels can be used in different ways.