Transmission loss of absorptive mufflers lined with expanded clay granulates

The article presents the results of tests on sound attenuation by two types of cylindrical absorptive mufflers with the same length and different diameters of chambers filled with expanded clay granulates. Using a laboratory stand for testing acoustic mufflers with an impedance tube, the transmission loss parameter was determined. To compare the effectiveness of sound attenuation, the transmission loss of mufflers without sound absorbing material was also determined. The results of these tests were compared to the results obtained with the use of a known calculation model for reflective mufflers. Using an impedance tube, the normal incidence sound absorption coefficients of the expanded clay granulates with thicknesses of material samples from 10 to 100 mm were determined. The dependence between the sample thickness and the first resonance frequency of the sound absorption coefficient was determined, which was then used in the proposed calculation model of the effectiveness of the cylindrical absorptive mufflers with expanded clay granulates. Using the proposed theoretical model, the results of transmission loss calculations, satisfactory for engineering applications, were obtained

Experimental tests of the acoustic properties of sound-absorbing linings and cores of layered baffles

The article presents the results of research on the acoustic properties of materials used as sound-absorbing linings and cores in baffles of anti-noise protection. Using an impedance tube the spectral characteristics of the normal incidence sound absorption and sound transmission loss indices of 12 specimens of mineral wool with different density and thickness were determined. From these characteristics, the single-number weighted sound absorption coefficient αw and the sound reduction index Rw were calculated. To calculate the value of the Rw index on the basis of surface mass of the mineral wool specimen, a new formula was proposed. The insertion loss of an acoustic enclosure with one, two and three-layer walls with dimensions of 0.7×0.7 m, containing mineral wool, was determined. The best efficiency was achieved for the enclosure made of walls of layers: mineral wool, placed on the sound source side, steel plate and aluminium plate

Computational methods of sound insulation of two-layer sound insulating baffles

W ograniczeniu nadmiernego poziomu hałasu, w szczególności na stanowiskach pracy, zastosowanie mają przegrody dźwiękoizolacyjne, które mogą być stosowane pojedynczo lub wykorzystywane jako element konstrukcyjny ścianek obudów dźwiękochłonno-izolacyjnych. Znajomość parametrów akustycznych takich przegród jest bardzo przydatna na etapie projektowania lub prognozowania skuteczności rozwiązań przeciwhałasowych. W artykule przywołano wybrane metody obliczania izolacyjności akustycznej przegród pojedynczych, składających się z dwóch warstw materiałów o właściwościach dźwiękoizolacyjnych. Oprócz wykorzystania modelu prawa masy i komercyjnego oprogramowania, zaproponowano nowe podejście w obliczeniu izolacyjności pojedynczych przegród dwuwarstwowych niejednorodnych, polegające na modyfikacji dobrze znanego modelu Davy. Weryfikację metod obliczeniowych przeprowadzono na przykładzie sześciu płyt gumowo-metalowych, których izolacyjność akustyczna była wyznaczona w warunkach laboratoryjnych w ramach wcześniejszych badań.In reducing the excessive noise level, especially at workplaces, sound insulating baffles are used, which can be used individually or are used as a structural element of the wall of sound-absorbing andinsulatingenclosures. Knowledge of acoustic parameters of such baffles is very useful at the stage of designing or forecasting the effectiveness of anti-noise solutions. The paper presents selected methods of calculating acoustic insulation of single partitions, consisting of two layers of materials with sound insulating properties. In addition to using the mass law model and commercial software, a new approach has been proposed in calculating the insulation of single heterogeneous two layer baffles, consisting in the modification of the well-known Davy model. Verification of computational methods was carried out on the example of six number and metal plates, whose acoustic insulation was determined in laboratory conditions as part of earlier tests

Linking Regional Knowledge Laboratory and Growth of smes – Empirical Investigation in Southern Region of Poland

The regional knowledge laboratory, being a part of the regional innovation system, impacts the regional innovation potential of regional firms, especially SMEs. Diffusion of innovations consists of the penetration of innovative solutions into the whole social and economic system, the result of which is a change in its functioning and overall development. The process of diffusion of innovations in a sense forces the innovativeness of the competing enterprises by necessitating their adaptation to the changing conditions of the environment. Diffusion of innovations is a determinant of the growth and development of enterprises, especially those of the SME sector. The paper is an attempt to empirically verify the dependence between the development of small and medium-sized enterprises and the innovative potential of the studied region. Due to utilitarian reasons, the region was defined in accordance with the European statistical terminology (NUTS1 – regions in the total number of 6) as the area of two administration regions (NUTS2 – voivodeships in the total number of 16): małopolskie and śląskie, which makes of one statistical regional (PL2 – Southern Region of Poland). The empirical material was based on a random sample of 109 micro, small and medium-sized enterprises located in the studied region. With the use of computer statistical tools, the hypothesis made in the paper was confirmed, namely that the level of commercialization of knowledge and the transfer of technology in the studied region influences the development of small and medium-sized enterprises

Experimental study and prediction of insertion loss of acoustical enclosures

The article presents the results of an experimental study and calculations, using theoretical models, of the insertion loss of acoustical enclosures. The research used a developed prototype stand for testing acoustical enclosures. The sound power levels of the source without and with the enclosure, needed to determine the insertion loss, were determined by the approximate method in accordance with standard requirements. To calculate of the insertion loss for enclosures with sound absorbing and insulating walls, a known calculation model using the transmission loss of baffles was used. A new calculation model for enclosures with sound insulating walls is proposed in the article

Accuracy of prediction methods for sound insulation of homogeneous single baffles

The article presents a comparative analysis of determined spectral responses of the airborne sound insulation of single homogeneous baffles using computational and experimental methods. Calculations using theoretical models, such as mass law, the Sharp and Davy models, SoundFlow software and laboratory tests concerned nine plates made of plastic, steel, aluminium and rubber, which are homogeneous materials. These materials are used in the construction of walls in vibroacoustic protection, such as acoustic barriers, machine operating field shields and sound insulating enclosures. Apart from analysing the spectral responses of the sound insulation of the plates, the weighted single-number sound reduction indices Rw, calculated by using prediction methods and laboratory measurements, were compared. Research has shown computational errors of about 6-7 dB for mass law and the Sharp model and about 3 dB for the Davy and Davy-Sharp models and SoundFlow software