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<br /> <br /> <br />Memorandum <br />February 26, 2025 <br />Page 4 <br />21202-23 North County Landfill_Noise DRAFT <br />the vibration signal. PPV is appropriate for evaluating potential damage to buildings, but it is <br />not suitable for evaluating human response to vibration because it takes the human body time <br />to respond to vibration signals. The response of the human body to vibration is dependent on <br />the average amplitude of a vibration event. The RMS of a signal is the average of the squared <br />amplitude of the signal and is more appropriate for evaluating human response to vibration. <br />PPV is normally described in units of inches per second (in/sec) and RMS is often described in <br />vibration decibels (VdB). <br />Vibration can be felt or heard by humans well below a level that would result in damage to a <br />structure. Except for long-term occupational exposure, vibration levels rarely affect human <br />health. Instead, most people consider vibration to be an annoyance that can affect <br />concentration or disturb sleep. According to the Federal Transit Administration (FTA), a <br />vibration level of 75 VdB is the approximate dividing line between barely perceptible and <br />distinctly perceptible.2 <br />ENVIRONMENTAL SETTING <br />Existing Ambient Noise Conditions <br />The project site located in a rural area. The primary sources of existing noise in the project <br />vicinity are vehicular traffic along East Harney Lane. The existing noise environment in the <br />vicinity of the project site was characterized through an ambient noise monitoring survey <br />conducted on February 7, 2025. The survey consisted of three short-term measurements (ST-1 <br />through ST-3). The noise measurement locations are illustrated in Figure 1. Sound level <br />measurements were conducted using Type 1 sound level meters with slow response and “A” <br />weighting. The noise monitoring equipment for the short-term measurements were collected <br />using a tripod at 5 feet above ground level. The microphones were protected from the effects <br />of wind noises. The noise meters were field calibrated immediately prior to and post use. <br />Ambient noise measurement locations, monitoring periods, and corresponding results are <br />summarized in Table 2 and the supporting noise measurement reports are included in <br />Attachment A. <br /> <br /> <br />2 Federal Transit Administration (FTA), 2018. Transit Noise and Vibration Impact Assessment Manual, FTA Report <br />No.0123, September.