A CASE STUDY OF LOW-FREQUENCY NOISE

Abstract

Sound waves below 20 Hz, which are generally inaudible to humans, are called infrasound. When infrasound and the less audible sound of the lowest frequencies (10 to 200Hz) appear as an element that disturbs people and is harmful to health, it is low-frequency noise (LFN). This air-borne noise has a much greater range than normal audible frequency sound and LFN travels much further on the ground. Stronger or longer-lasting infrasound around 7-20 Hz directly affects the human central nervous system and can cause disorientation, anxiety, panic, depression, nausea, discomfort, vomiting, etc. Sooner or later, the waves can lead to damage to the nervous and/or cardiovascular system. It is estimated that about 2.5% of the population may have a low-frequency threshold that is at least 12 dB more sensitive than the average threshold, which corresponds to almost 1,000,000 persons in the age group 50 to 59 years in the EU-15 countries. LFN is recognized as a particular environmental noise problem, especially for sensitive people in their homes. Conventional noise assessment methods are not suitable for LFN and lead to wrong conclusions and consequently to wrong decisions. An LFN source is more difficult to localize, difficult to suppress, and spreads rapidly in all directions so that it can be heard over great distances. All existing sound field visualization methods have a lower frequency limit of 125 HZ. Low-frequency waves surround the noise source and such a source is practically "undirected". In the paper, we described the LFN assessment carried out, which we identified in a commercial/residential building. The measurements were carried out in the immediate vicinity (3-4 km as the crow flies) of the object in question, at the site of industrial facilities (V1 and OM2), the pond complex, and the gas and transformer station. The LFN in the facility was initially unidentified, and the source search diagnostics were based on the method of comparing the generic spectral distributions of the LFN in the facility with other selected measurement positions.