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___ 16 Attachment 3 Sound G~'dvice Helpful Information from Stewart Glcoustical Consultants sfs-666-a6sg copyright20D4 A member firm of the National Council of Acoustical Consultants www. sacna,com 7406 L Chapel Hill Road, Raleigh, NC 27607 The information in this document is not provided as a consulting service or as a solution to any specific problem. EVALUATION OF ENVIItONN1ENTAL SOUND IN THE COMMCUNTT'Y By Noral D. Stewart, Ph.D. Revision of February 27, 2004 There aze ancient references to noise being a problem in cities. In this century, noise was recognized as a problem in cities in the 1920's. The sources were new modes of transportation, ventilation systems, industrial plants, and loudspeakers.. The coming of,jet aircraft renewed interest in enviromnental noise. With increasing population density, communities become noisier,. There has been much research on problems related to noise in the community. Most of this has concentrated on sources related to transportation, military systems, and ventilation systems. That is because these sources are widespread, and there are readily available mechanisms to fund the research. Most of this research has concentrated on establishing acceptable quantities of sound and reducing sound to those levels for these common sources. However, most of the research has concentrated on densely populated azeas where more noise is expected. Many of the criteria developed are aimed primarily at evaluating whether certain land uses such as residentialcan be made compatible with a given level ofnoise. Tlvs is a different matter than evaluatingwhether new noise is compatible with existing development. Some criteria based onlong-termaveragesalso fail to recognize problems due to recurring loud events thatmay only occur once a week. Problems due to the amount of sound from a fixed source aze usually solvable with enough money. The producer of the sound usually does not need or want the sound any more than neighbors who might be complaining. Primary exceptions where it is most difficult aze sources involving outdoor entertainment or recreation. More recently, manufacturers ofmany products such as automobiles, appliances, and ventilation systems have been paying more attention to "sound Quality." They have realized that once the quantity of sound is reduced, the quality becomes important. People have an expectation for way sources should sound. In quieter communities, this expected sound quality also becomes important. People expectto heaz ablend ofsounds that become unnoticeable., Sounds that stand out and typically demand attention cause problems ff they aze heard cleazly regardless of the level of sound. It is unportant to consider both the amount of sound and the way it sounds. Problems due to the nature of a sound aze sometimes related to industrial machinery that might have an impulsive chazacter or sound like a siren. The more difficult problems to resolve aze those related to speech, music, or other recreational activities where the sound is desired by the producers or their customers. This documenthas evolved from work on several projects. Portions of this material have been and often are incorporated into reports on major projects. It is intended to provide a basic primer on noise in the community..