A Compelling Case for the Use of the C-Weighting Noise Metric for Outdoor Amphitheater Noise Measurements

This paper describes how, in February 2001, a city in Michigan granted a development company a Special Approval Land Use (SALU) Permit to build and operate an amphitheater within a parcel of land adjoining a residential community. Without the input of technically knowledgeable people to properly define and specify a noise limit, crafters of the SALU Permit arbitrarily imposed a noise level limit of 100dB at the back of the amphitheater. The stated intent of this limit was to protect residents of nearby neighborhoods from adverse and intrusive noise impact from music produced by concerts at the amphitheater. Unfortunately this limit was unspecific in terms of noise measuring metrics that were to be employed for compliance checks. This left the limit subject to interpretation, which was attempted by a variety of individuals including several with limited if any technical training and expertise in measuring and evaluating outdoor sound. The 7000 seat capacity outdoor amphitheater is considered small to moderate in size. Situated atop a long abandoned land fill, it is formed by an open (unroofed) fan-shaped area of concrete that contains fixed seating, with a 120º semi-circular earthen berm (hill) that slopes upward behind the fixed seating area and defines an area of lawn seating along the back of the amphitheater. The top of this hill is approximately 73 meters (240 feet) from the stage, and 8.5 meters (28 feet) above stage elevation. The top of hill is the designated location at which the SALU 100dB limit applies. The south facing stage has a partial roof, and back wall with side walls extending half way toward the front of the stage. The roof serves to partially shield the stage from adverse weather as well to support two clusters of speakers. The amphitheater hosts a variety of popular performers with genres ranging from jazz to country, and old to modern rock, hip-hop, and rap. Many of these genres employ loud rhythmic bass. South of the amphitheater is a large residential subdivision. The closest homes in this subdivision are approximately 427 meters (1400 feet) south of the amphitheater stage. While this is a somewhat large distance, noise from the amphitheater can be heard throughout much of the residential neighborhood and results in numerous, and frequent complaints, particularly concerning the loud rhythmic bass. As result of these complaints the local municipality, which granted the SALU, commissioned professional acoustical engineering services to evaluate and quantify the problem. At the request of the local municipality Kolano and Saha Engineers, Inc. conducted an in-depth study in order to determine the response of the amphitheater sound system and transmission of sound to the nearby community. In addition the engineers conducted noise level monitoring at the top of the hill to determine how well the concerts complied of with the SALU Permit noise limit. The results of this study helped to identify contributors to the noise impacting the residential community and demonstrated the ambiguity of the SALU limit.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References;
  • Pagination: pp 422-427
  • Monograph Title: Noise-Con 04. The 2004 National Conference on Noise Control Engineering

Subject/Index Terms

Filing Info

  • Accession Number: 01054147
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jul 19 2007 11:01AM