Moving on from the previous article, let's now spend some time in exploring and understand the different methods available for you to isolate a room. Depending on how handy are you with tools and construction works, some of the methods below may be possible for you to do it yourself. However, you should check on any existing regulations that might require you to engage specific contractors in carrying out the works you have in mind (e.g. some office buildings have regulations for contractors to work in existing premises certified by the lease owner).
As mentioned in my previous article, every single surface of the room are as important as they might be the weakest link to leak sound in and out of the room. Thus, below are some practices that can help you improve on your room isolation index.
How much to isolate?
When space within is acoustically sensitive, the walls take on additional importance. They must work as sound barriers to isolate the interior space from exterior noise, and to separate the exterior from the interior sound. Before deciding on the design and construction of the wall, there are two factors for us to consider, how loud is the surrounding ambient noise and how quiet do you want your room to be? To clarify the two consideration even further, the first refers to the level of exterior noise the room must reject under your specifications, and the later would refer to the lowest sound pressure level (SPL) your room operates in when all equipment are turned on. The difference in the two measurements would also give you a good idea on what would the sound transmission class (STC) rating be for the wall (part 1).
Airborne vs. Structureborne sound
Sound can propagate through any medium, for example, it can pass through air and solids. When it comes to room construction, the solid medium would be more of the interest to us as that involved structure-borne transmission. A simple analogy would be the low thumping sound you felt and heard while you are outside, distance away from a night club. The low frequencies are being radiated structurally (in this case, floor and walls); hence you can hear it outside even though the subwoofers are inside the night club. Airborne sound is higher in frequency, and the structure-borne noise is present only as a vibration that is felt. Therefore, any barriers (walls) must be designed to minimise both airborne and structure-borne transmission.
Airborne transmission is minimised by sealing any air leaks in a partition, if the barriers are not sealed properly, the acoustical performance of these walls will exponentially decrease. Structureborne transmission can be reduced by utilising decoupling elements, breaking the transmission path. Also, structure-borne sound can also be reduced by eliminating any resonant conditions in the transmission frequency range.