![]() ![]() As the industrial devices generate mainly low-frequency noise, and the semi-active and active methods are the most effective at low frequencies, the frequency range of interest in this research is limited to 500 Hz. In semi-active methods, specific materials or elements are used to modify on demand properties of the structure in such a way that vibration or noise propagation is reduced. In active methods, the goal of noise and vibration reduction may be achieved by external activation of sources in vibroacoustic control systems used in different ways. However, these techniques are ineffective at low frequencies, which is wider explained in. In the traditional passive noise reduction techniques, absorptive materials or vibration absorbers may be used. Therefore, to reduce noise and vibration, three main groups of methods may be employed, i.e., active, semi-active or passive. The aim of contemporary researchers is to minimize noise and vibration pollution in the human environment by improvement of the materials and methods. ![]() Vibrations in the form of shocks have dangerous impact on humans in vehicles, as resonant frequencies of the human body may be excited. ![]() Low-frequency vibration, specific to the machine operator’s profession, is especially harmful and causes decrease of work efficiency. Both noise and vibration have an impact on humans. Noise exposure is a common issue, which may significantly annoy or even result in irreversible hearing loss of workers and people using noisy appliances in their everyday life. ![]()
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