Is Acoustic Treatment and Soundproofing the same?
Have you ever heard of a friend who tried to soundproof his room by putting acoustic foam or even egg crates on the wall? Well, the attempt probably failed miserably because it is impossible to soundproof a room by just sticking any type of acoustic panels onto the wall.
Acoustic panels are meant for acoustic treatment, which is the control of echoes and reverberation in a room. Whereas soundproofing is about preventing sound from entering or exiting a room. In this article, we attempt to discuss the differences between acoustic treatment and soundproofing!
What is acoustic treatment?
Acoustic treatment is the control of reverberations and echoes found in a space. I do not want to define acoustic treatment as “to reduce echoes and reverberation”, because even though most of the acoustic treatment jobs require the reduction of echoes and reverberation, some jobs require the redirecting of such echoes, such as in an opera house or a choral chamber. Nonetheless, let’s discuss how we can effectively reduce the reverberations and echoes in a room as that’s what most people want.
There are many types of acoustic panels that you can purchase from your local shops or online that you can hang on your wall and have it look beautiful at the same time. Generally there are 2 types of acoustic panels. There are acoustic panels that are soft to the touch such as fabric panels, foam panels, or even polyester panels. Then there are acoustic panels which are hard to the touch, such as timber grooved panels, perforated metal panels, or even acoustic plaster. The general rule of thumb is that soft acoustic panels have better NRC (Noise Reduction Coefficient) than hard acoustic panels, and if you want the most bang for your buck, choosing the soft type is the way to go.
Many different rooms have different requirements of how little echo it should have. A measurement of the amount of echo found in a room can be ascertained with a test called the RT60 test. Basically the RT60 measures the amount of echo by seeing how long an impulse sound would take to decay by 60 decibels. An impulse sound is just an acoustician’s way of saying a loud sound.
Usually small rooms require a lower RT60 time and larger venues like an auditorium will not require as low an RT60 time as say, a smaller room like your bedroom. The amount of RT60 required also depends on what the venue is used for. For instance, vocal recording studio would require a very low RT60 time of 0.2 – 0.4 seconds, whereas a teleconference room would suffice with an RT60 time of 0.8 seconds.
Putting more acoustic panels in the room will reduce the RT60 time as there are more surfaces for absorption. A good estimate install enough acoustic panels to cover 60% of the exposed walls. This should allow you to reduce the echoes in the room and achieve a respectable RT60 time of 0.8 to 1.2 seconds, assuming it is a small to medium-sized room of about 500 – 1,000 sqft.
Soundproofing or sometimes called “sound isolation” is very much different from acoustical treatment. It is much harder to soundproof a room than it is to acoustically treat a room. We will discuss the different elements required for a soundproof room to work and the things to look out for.
To begin, we will first understand the 2 ways the sound can travel.
Air: It is of no surprise that sound can travel by air as a medium. This is the way we communicate with one another as the sound waves generated by our voice box is carried through the air and into the ears of our recipient. To prevent sound from travelling through the air from one space to the next, a sound absorbing substrate such as rockwool or polyurethane foam can be used. The sound energy is converted into heat energy when it is trapped in the porous surface of the insulation material.
Solid (structure): What is not commonly understood is that sound can travel by a solid structure too. This is commonly known as vibrations. Low frequency sounds are more like to travel through a solid structure such as a beam or soffit than mid or high frequency sounds are. To prevent the transmission of these low-frequency sounds, we need to decouple the structure. There are many ways to decouple the structure, but commonly used products include high-density rubber mats, sound isolators, resilient channels, and springs.
To fully soundproof a room, we need to build a room within a room (RWAR). A room within a room construction consists of building a smaller room in a larger room, and decoupling the smaller room from the larger room with isolators for the inner walls, joist isolators for the inner floor, and springs for the inner ceiling. It is also important to consider the use of building materials with heavy mass, as these high-density material will help to convert some of the low-frequency (LF) sound energy into heat energy before the transmitting through any isolators or springs. This means the walls and ceiling of the inner room can be lined with lead-sheet or mass-loaded vinyls for maximum LF absorption. In between the inner room and outer room, a high-density packing of insulation of 80 – 100kg/m3 should be installed. To prevent any possible short-circuiting of sound within the inner walls, floor, and ceiling, a neoprene rubber strip or foam tape strip should be used where the boards of the wall/ceiling/floor touches one another, along with a generous caulk of acoustic sealant to seal up any possible joint leaks.
Soundproofing is not an easy job and should be done by a professional team who has experience building RWAR construction. It should not be attempted as a DIY project as there are many areas if not done properly can cause sound to leak through gaps or flanking paths.
Putting it all together
To build a room that noise cannot enter and have no echoes, you will have to do both soundproofing and acoustical treatment. A room that is acoustically treated but not soundproofed will still be affected by outdoor sounds coming in, and a room that is soundproofed but not acoustically treated will be plagued by echoes since no sound can escape.
It is recommend to soundproof the room first by isolating all the structures and walls in the room, then finish it off with acoustical treatment by installing acoustic panels on the walls and ceiling. The endeavour to have the perfect acoustic room is a tough one, but once properly done will give you a room that can acoustically serve you for many years to come.