The University Center for Energy-Efficient Buildings of CTU, in cooperation with the company Saint-Gobain Construction Products CZ a.s., ISOVER division, carried out a set of computational simulations, the results of which will help to predict the effect of perforated trapezoidal roof sheets of the ISOVER Roof Acoustic system solution on noise reduction in industrial halls .
The working environment inside industrial halls is significantly affected by noise from the operation of production machines and technological processes. A number of measures can be used to reduce its impact on workers, for example by covering noisy machines, screens, sound-proof control rooms, protective work aids, etc. Sound-absorbing coverings of internal surfaces can also play an important role.
The study of the Acoustics Laboratory of the Czech Technical University UCEEB was devoted to the effect of perforated trapezoidal sheets in the ISOVER Roof Acoustic system roof compositions on the spatial acoustics of industrial indoor buildings, in particular to shortening the reverberation time and reducing the acoustic pressure level from the operation of noise sources. For this purpose, an acoustic model of a "typical" single-nave hall with a steel supporting structure and light cladding was created. Acoustic calculations were performed in the specialized software ODEON Combined version 14 and supplemented with predictions according to commonly used calculation methods.
The results of the calculations proved that the increase in absorption by using roof system compositions with perforated trapezoidal sheets ISOVER Roof Acoustic can significantly contribute to shortening the reverberation time and reducing the sound pressure levels (mainly in the field of reflected waves), i.e. to improving the acoustic conditions in industrial halls.
The calculations included several variants of the roof covering solution: solid trapezoidal sheet (reference variant), perforated trapezoidal sheet with mineral fiber filling and perforated trapezoidal sheet without filling. In each model, several noise sources were considered, running either all at once or individually. In terms of frequency composition, the sound spectrum corresponding to establishments emitting mainly noise at low and medium frequencies or at medium and high frequencies was chosen.
The conclusions of the study proved that the use of perforated trapezoidal sheet metal in the composition of the roof of the ISOVER ROOF ACOUSTIC system solution has a significant effect on the spatial acoustics of the hall. The reverberation time of the hall with perforated trapezoidal plate is approximately half that of the conventional solution with solid plate (T = 3.42 s - solid plate, 1.72 s - perforated plate; average values for octave bands 500 Hz and 1000 Hz). In general, a shorter reverberation time contributes to the intelligibility of speech (e.g. during employee communication at the workplace, service or security announcements, etc.). For comparison, ČSN 73 0527 recommends a reverberation time of 1.6 s for halls with sports use (relative to the internal volume of 4,423 m3). The calculated reverberation time of the hall with perforated trapezoidal sheet is very close to this value, which ensures optimal acoustic conditions in the hall.
Perforated sheet metal also significantly contributes to the reduction of noise in the hall (with the exception of places in close proximity to sound sources). It is clear from the results of the calculations that the results for both frequency spectra of sound sources are similar, while the influence of the number of simultaneously running sources is not negligible. An average reduction of the sound pressure level A by 3.3 dB (6 sources) was achieved, or by 4.0 dB (2 sources). A decrease of 3 dB simplified corresponds to a fictitious reduction in the number of running sound sources by 50%, or a difference of 4 dB by 60%.
A complete acoustic study of an industrial hall with ISOVER ROOF ACOUSTIC roofs is available from ISOVER technical staff upon request.
Up until now, room acoustics in domestic indoor buildings have been solved by other structures as a standard.