Acoustic Insulation Explained

For the occupant of a house or apartment who is bombarded by noise from outside—or even inside his home, acoustic insulation is often the most viable solution to escaping this noise. There are ways of insulating against such aggravations; but before attempting any of the optional insulation methods, you'll need to know something about noise and acoustics.

Sound Transmission

Like the waves in water, noise travels in waves. But these are waves in the air.  Whenever there are vibrations that create these waves, and whenever these waves come in contact with your eardrum, you hear them as noise or unpleasant sounds. The problem that often arises in trying to reduce or eliminate noise is that these sound waves, unlike water waves, can penetrate certain materials. These waves are replicated in the material. They then travel through the material in the form of vibrations, which in turn reproduce them into air vibrations on the far side of the material from which they have entered.

Stopping Noise Transmission

Stopping these sound vibrations from passing from one space to another space is the challenge of acoustic engineers. The key is to find and use a material that will not vibrate from sound vibrations. This is not always simple to accomplish. The acoustics engineer must also determine the type of structure that normally separates two areas. These structures can be walls, ceilings, floors and often doors, windows, heating ducts, etc. For each type of structure, the engineer may need to use a different type of sound insulation.

Acoustical Insulation Installation Challenges

Once you, or the acoustics engineer, have found an insulation that is more likely to deter, or at last reduce, the transmission of sound; you must then know how to install the insulation. If, in installing it, you leave openings, cavities, or gaps through which sound waves can travel, your acoustical insulation will be ineffective. You will need to know how to cut, mold, attach and shape your insulation to effectively stop sound from passing through these airways.

Choosing Acoustical Insulation

How does one choose the sound insulation that will work best? You will need to first know certain things about the noise you wish to damper or reduce. You will also need to know how loud the noise is. This loudness is usually measure in decibels. For example: a typical conversation produces about 60 db (decibels), depending on how close you are to those conversing. In addition to knowing sound loudness, you'll need to know how efficient each type of prospective sound insulation is in stopping or reducing sound. This is typically measured on a noise level scale referred to as STC or Sound Transmission Class. A sound insulation that has a greater ability to reduce sound is ranked higher on this scale. An interior gypsum wall with 3/8 inch gypsum board, for example, is usually rated at about 35 on the STC scale. This same wall with a two layers of 5/8 inch gypsum board will rate about 60 on the STC scale.