Carpet is not a cure-all for noisy houses. In fact, it is typically only 15-20% absorptive. It would take four times as much carpet to have the same impact as a typical acoustic material, which is about 80% absorptive.
Controlling sound transmission, whether it is produced by a teen blasting music from their bedroom or a nearby freeway, noise can be difficult to do. Good design and selection and installation of building materials can reduce the intrusions whether they originate in the house or from outside.
See Chapter 2 The House as a System Green from the Ground Up book for more details.
Windows are often the culprit
When noise from the outside is a distraction, windows are often to blame. Exterior walls typically block at least 45 to 50 decibels of sound, but even a very high quality window might not be able to block 40 decibels.
Dual-pane windows with increased air space between sheets of glass improve acoustic isolation. "Superglass" windows, in which glass is combined with a very thin layer, or layers are even more effective. Noise, however, migrates through the weakest structural element, and that could be a door or ventilation duct as well as a window. The acoustic isolation provided by a door is only as good as the effectiveness of the door seal. If air can get around or under the door, so can sound.
Walls that Reduce Sound
Typical wall construction of 2x4s on 16-in. centers with fiberglass insulation is not very effective in reducing sound. Structural Insulated Panels (SIPs) or framed walls with exterior rigid foam are more effective. Cellulose and foam insulation do a better job of reducing noise than conventional fiberglass batts. The ideal combination for houses close to noise sources would take advantage of SIPs, sided with cementitious boards, along with Superglass® windows. This combination results in a very quiet house and, coincidentally, is a recipe for a very energy-efficient home.
Another option for homes close to environmental noise is the staggered stud approach, which has the added advantage of reducing thermal bridging. A further option is to add flexible C-channel to inside walls perpendicular to the studs.
Barriers and Distance to Block Sound
Noise barriers, such as:
- earth berms
- solid walls
- neighbor's buildings
can help with noise reduction. To be effective, barriers must block the line of sight between the noise source and the house
Note: Vegetation provides little if any reduction.