Sound-proofing your living space can be a difficult task. The first step is to understand how sound gets where you don’t want it, and what options you have to minimize it.
As sound propagates from the emission source, it reduces in proportion to the square of the distance it travels. This basically means that it is reduced to a quarter of the amplitude when it travels twice the distance.
That is why it is critical to put the maximum distance between yourself and the sound source. By plugging one hole in your bedroom, but leaving others (for instance in your bathroom window) open, you are increasing the distance the sound must travel through openings to reach your ears. Although the thought of a hole in your house may seem extreme, sound only needs the slightest openings to slip through and give you uncomfortable nights! Check cracks in your window panes or doors that appear slightly ajar. If light can penetrate the opening, then sound can seep in as well. One way to check is by turning on the light in your room and inspecting from the outside.
By increasing the amount of material between the sound source and yourself, you increase the transmission loss through the medium. This loss is heavily dependent on the atomic structure of the medium. Dense materials, with little space between atoms, block more sound, but if they are too stiff they will also allow the sound to be converted from the air and resonate through them. The best material is flexible, but dense enough to reflect the sound back toward its source. If this is the case, the transmission loss is proportional to the density and thickness of the material. However, since the decibel scale is logarithmic, you will actually see a 10 decibel transmission loss when you double the thickness of the material. Note: Reducing sound by 10 decibels makes the sound half as loud.
Once sound enters your house, it will reflect around until it is absorbed into the environment and dissipated as heat. We’ve all been in loud gyms where the sound bounces around for several seconds, and the ear detects this reverberation as an echo. If you add sound absorbing material into the room, this will trap the sound between the light, porous fibers and quickly lessen the sound reflection. It is important to remember that the physics between acoustic absorption and reflection is very different, and you must attack each of the issues separately.
In the end, you need to determine if you are trying to dim down sound in your house (to make for a more comfortable conversation), or trying to keep it out in the first place. Perhaps you want to keep noise from one side of the house out of another. Review how the noise is getting there; through walls, small openings, windows, and doors. Then mitigate the noise by selecting commercial products or solving the problem at its source.