Use Of Elastomers as Sound-Absorbing Materials in Silencers for Ventilation Systems

Existing silencers for aerodynamic noise for ventilation and air conditioning systems and the sound-absorbing materials (SPM) used in them are considered. Depending on the design features, they are divided into lamellar, tubular, channel and chamber, as well as the turns and sections of channels used inside the SPM, and their advantages and disadvantages are indicated. In particular, the use of fibrous materials such as mineral wool or superthin fiberglass as SPM requires the use of protective coatings in the design of silencers to prevent such materials from being blown out by the air stream. The design of the protective coating is usually a perforated steel sheet or metal mesh and fiberglass or fiberglass. Such constructions are quite technologically complicated, and besides this, during long-term operation, fibrous SPMs tend to fall off under the influence of vibrations caused by air flow in the places of installation of silencers, which leads to a sharp decrease in their effectiveness. Chamber silencers are somewhat detached, but they are used extremely rarely because of their large dimensions. The advantages of such silencers include a sufficiently large noise reduction efficiency, especially if the inlet and outlet openings of the silencers are not axisymmetric. Currently, in the framework of the fight against noise of various engineering equipment, the so-called elastomeric materials based on nitrile rubber are widely used. Basically, these materials began to be used in various structural sound insulation systems, but such materials can also be used as sound absorbing materials, since they have relatively high sound absorption coefficients. In particular, the sound absorption coefficient of the K-Fonik Open Cell-240 material in the frequency range starting from 315 Hz is 0.4 and begins to increase, reaching from 800 to 1250 Hz 0.95, and at higher frequencies up to 5000 Hz on average 0,85. Elastomeric materials have several advantages over fibrous materials. They are not blown by the air flow in the channels of the ventilation systems and, therefore, do not require the use of protective layers in the structures, are resistant to vibrations and are more technological in manufacturing. Nevertheless, the results of acoustic tests of a silencer, the plates of which are made of K-Fonik Open Cell-240 elastomer, showed its low efficiency. The above solutions allowed it to be significantly increased due to design changes of the plate.

M.Yu. LESHKO¹, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.),
A.V. SIDORINA¹, Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.),
A.V. VARGASOV², Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.),
P.A. KOSHEEV², Engineer (This email address is being protected from spambots. You need JavaScript enabled to view it.)

¹ Research Institute of Building Physics of the Russian Academy of Architecture and Construction Sciences (21, Lokomotivniy Driveway, Moscow, 127238, Russian Federation)
² Scientific and Production Association “Almaz” named after Academician A.A. Raspletin (110, Dmitrovskoe Highway, Moscow, 127411, Russian Federation)

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