Page 28 - Winter 2009

around the turbines; however, wind and other causes of sound refraction may cause the turbines to be heard at much greater distances.
National parks
The National Park Service (NPS) has been working on the problem of maintaining the character of wilderness areas and their sounds since the early 1990’s. The first studies came as a result of the presence of air tour operations in the Grand Canyon. It was found that the ability to hear the aircraft was a key factor. This is at odds with the typical noise exposure criterion in use by the Federal Aviation Administration for people around airports. A new standards effort has just been started (S3-SC1-WG4) on this topic under the direction of two scientists at the NPS.
Soundscapes
The term soundscape is just like landscape, but for sounds (Figs. 5–8). It is used to describe an area, usually in a city, to try to avoid the negative implications of the word noise. Recent work has shown that sound level is often less important than the viewpoint of the listener. Influences of the norms of society may play an important role.
In addition to the “sound walks” which have occurred in recent years at Acoustical Society of America meetings, a new workshop series has started to bring acoustics into the plan- ning processes in cities. The first such workshop occurred in Portland, Oregon.
Green building codes and standards
For the first time since the U.S. Green Building Council’s Certification Leadership in Energy and Environmental Design (LEED) standards were introduced, credit can now be taken for acoustical design for schools and hospitals. The class- room standards give one credit for a design that is similar to that discussed in the national standard on classroom acoustics (Fig. 9).
Credit for hospitals is given in the current revision of the green building documentation for hospitals (Fig. 10). A national standard will soon be available whereby two credits are possible—one for speech privacy and one for ambient levels. The speech privacy criterion is given when conversa- tions between doctors and patients are not easily overheard. The ambient level criterion is given for proper design so that the interior of the hospital is quiet enough to be restful. This is not the case in many current designs.
Energy savings from noise control
The material for sealing of sound leaks on an outside wall is the same as that which is used for energy conserva- tion, namely caulking and weather stripping. In both cases, the best improvement is for a solid material to be placed between the inside and outside of the building. Both acousti- cal performance using the sound transmission class (STC) as a criterion, and infiltration (the amount of air that may came in through the cracks) are available for doors with different degrees of treatment.
Fig. 5. Soundscape: Open Air Market.
Fig. 6. Soundscape: Park/Playground.
Fig. 7. Soundscape: Dogs/Children.
Fig. 8. Church.
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