Abstract
Concern over noise pollution led to the development of methods for making environmental assessments. At the same time, the need arose for methods to measure low frequency sound and clarify propagation conditions.
The main objective of this research was to investigate low frequency sound propagation conditions and the problems associated with measurement and analysis. We also studied the characteristics of low frequency sound (below 100 Hz) near reflecting surfaces and developed a technique for positioning the measurement microphones. Additionally we found it necessary to develop a new measurement method we call “the synchronized integral” method.
A theoretically perfect point sound source was needed for the measurements. To satisfy this need, we constructed a source for quantitative investigation and measurements were made at distances up to 100 m from the sound source.
Analysis of the data we collected clarified the following phenomena: −6 dB/-doubling distance (d.d) attenuation is not reached; frequency and microphone height influence attenuation; measurements taken near the ground are most stable; superposition influence occurs at frequencies above 125 Hz.
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