Infrasonic and low frequency environment in the shadow zones of noise barriers

Abstract

Constant increase of life quality expands the number of activities that are necessary to satisfy the requirements of society. Increasing number of new technologies, machinery or equipment used in daily life together with positive outcomes generates secondary, unwanted consequences. Low frequency noise (LFN) is one of the most common environmental issues in urban areas and can be generated by the sources of both natural and artificial nature. Low frequency noise from artificial sources such as road and railway transport, airplanes as well as wind turbines, compressors or air conditioning stations is constantly growing. Transport noise is attributed as a source of low frequency noise yet the highest sound pressure levels usually lies in the frequency range from roughly 16 Hz to 5 kHz with dominant low frequencies in the range from 16 to 500 Hz. This frequency range is of common interest yet it has crucial role on annoyance, moreover the number of inhabitants under the sway of LFN and infrasound near highways is constantly increasing. The reduction of transport noise is usually implemented by installing noise barriers which lack infrasonic and low frequency attenuation and can even potentially amplify the subjective reaction to the transport noise because of inappropriate balance of low, mid and high frequencies. The aim of this research was to investigate the levels of low frequency noise and infrasound in the shadow zones of noise barriers. Assessment of LFN was done by using the G-weighted level as a metric for infrasonic frequency evaluation and dB(C) – dB(A) difference as indicate of low frequency noise.