Analysis specification of noise structural constituent spectra in highly glazed cabins

Introduction. Cabs of a wide range of technological machines of various functional purposes, in particular, track cranes of road-building equipment, have a large glass area. It will be observed that glazing should be designated as a “weak” element both in noise proofing and mechanical impedance which explains the significant effect of air and structural noise constituents on the formation of the acoustic characteristics inside such cabs. Materials and Methods. The present study objective is to analyze noise spectra created by the emission of the cab glazing elements in the closed space in the form of a rectangular parallelepiped. The investigative technique of the acoustic characteristics is based on the fundamental principles of the engineering vibroacoustics for proportional spaces. Research Results. Since the cabs of any machines and equipment are energetically closed systems consisting of small-scale plates, the vibroacoustic characteristics spectra analysis is based on the power balance methods. The existing studies are well founded for estimating the sound pressure levels created inside the production areas when the anacamptic sound impact can be neglected. When evaluating noise levels inside the cabins, this assumption is oversimplified, and, therefore, the studies presented in the paper are based on the system of the piston-type sources emitting sound energy into a closed space, while the dimensions of the radiators as such are commensurable to the overall sizes of the cab. This topic is most relevant for locotractors and diesel locomotive cabs. Discussion and Conclusions. The results of the theoretical studies allow performing engineering calculations of the vibration and noise spectra of all elements of the cab enclosure, and evaluating the quantitative contribution of each one to the formation of noise spectra within the cabin in the operators' workplaces. Such analysis permits to estimate the contribution of each source at the designing stage of the cabins and to define the excess over the admissible limit values. On this basis, also in the design, the most simple, technologically and economically feasible options are chosen to ensure the sanitary norms of noise by obtaining the required soundproofing parameters which is accompanied by the decrease in the proportion of the noise air constituent, as well as the impedances of the corresponding elements. This, in turn, leads to the reduction of the part of the noise structural constituent.