Think of a memorable visit to a concrete, block or stone finished project and it’s highly probable that the structure’s poor acoustics is the focal point of the experience that is etched in your memory. Concrete block walled gymnasiums, for example, are notoriously reverberant making graduation loudspeaker announcements memorable for being unintelligible. Despite those unfortunate memories, every building material can be acoustical, and with proper selection and planning, you can achieve the project’s acoustic goals for noise isolation and architectural acoustics, even if your materials are hard.
The most intuitively obvious acoustical attribute of concrete, block and stone is the brute force ability of their dense mass to block sound. Unlike many other common sense notions about acoustic design, this one is absolutely correct. In fact, the sound transmission loss of simple, single component walls and ceilings can be accurately predicted by the so-called “mass law equation.” According to that equation, sound isolation increases 6 dB for every doubling of sound frequency, and another 6 dB for every doubling of the wall’s surface density (i.e., density by thickness of the wall). Brute force improvements in noise isolation can be made by choosing a more dense building material, by increasing the structure thickness, or by doing both.