This is why you can hear it and others can’t – You’re a dBC Receptor. Seems like it's regulated by ANSI in the USA - Now there's something to think about folks! Something new to trip "them" up on?
Below is a portion of a document at this website's URL: www.efsec.wa.gov/bpcogen/DEIS/3.%209%%20Noise.pdf Humans respond to a sound's frequency or pitch. Environmental noise is composed of many frequencies, each occurring simultaneously at its own sound pressure level. As measured by an electronic sound level meter, frequency weighting combines the overall sound frequency into one sound level. The commonly used frequency weighting for environmental noise is A-weighting, or dBA, which approximates how an average person hears sounds. C-weighting, or dBC, is a measure of the lowest frequencies of sound and vibration. Low frequency noise is usually described as humming or engine-like sounds or a feeling of pressure or vibration. How 'bout that?! Impact Criteria for Low Frequency Noise Although the state of Washington regulates low frequency noise through noise regulations using the A-weighted decibel scale, the American National Standards Institute (ANSI) presents recommendations to provide protection from low frequency noise disturbance in Gas Turbine Installation Sound Emissions (ANSI 1989). ANSI recommends limiting noise levels at residences near new gas turbine facilities to 75 to 80 dBC. As with the original Golder modeling study, the newer Hessler modeling also evaluated low frequency noise levels at the receptors. In general, the new modeling results indicate that low frequency noise from the cogeneration facility (C-weighted sound levels and the lower frequency levels) would be similar to or less than the levels reported by Golder for the original project configuration. Consequently, both studies conclude that low frequency noise would not reach perceptibility thresholds at any of the residential receptors. The normal threshold of perceptibility for low frequency noise and vibration is 75 to 78 dBC (ANSI 1989). The ANSI recommends C-weighted plant levels should be significantly below 75 dBC at residential receptors. -- You received this message because you are subscribed to the Google Groups "Hum Sufferers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/hum-sufferers?hl=en.
