Field Evaluation of Reflected Noise from a Single Noise Barrier—Phase 1 (2016) / Chapter Skim
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7 C H A P T E R 2 Research Approach As noted in Chapter 1, the objectives of this research are to: 1. Determine the spectral noise level characteristics of the overall noise in the presence of a single reflective noise barrier for positions on the opposite side of a roadway through the collection of field measurements from diverse sites, and 2.
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8 is discussed. In addition to the sound level data, the data collection for the FHWA Method included recording of calibrated .wav audio files at each microphone position.
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9 • Meteorological data collection station with precision temperature sensors and precision quality anemometers capable of measuring wind speed in three dimensions at two heights (5 ft and 15 ft) above the ground; • Video camera and laser speed gun; and • Accessories including a 94-dBZ calibrator, extension cables, windscreens, microphone tripods and stands, extension poles, and guy wires.
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10 pressure levels. One-second broadband A-weighted levels and unweighted sound pressure levels and 1/3octave band unweighted sound pressure levels between 12.5 Hz and 20,000 Hz were saved, and were later processed into one-minute intervals, and the audio signal was recorded.
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11 adjusted to account for the angle of speed shooting off of head-on. As needed, the speed samples were time-adjusted forward or backward to represent the time of passage from the shooting point to a point midway between the Barrier and No Barrier sites.
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12 more bad one-minute periods)
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13 The audio .wav files were processed and examined in 1/3 octave bands in 1/8-second intervals. The data were then displayed using spectrogram-type graphs.
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14 account for the addition of the temporally varying sounds statistical values of Loudness have been calculated. While these individual psychoacoustic metrics are useful for comparing sounds of widely different natures, they do not necessarily indicate whether an individual might be annoyed by a given sound, nor to what extent.
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