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1

Substitutional transmittance function of helicoidal resonator

Łapka W.

Vibrations in Physical Systems

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2010

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Vol. 24

265--270

EN

An analytical and computational characteristics of transmission losses of the helicoidal resonator are compared in this paper. The substitutional transmittance function of helicoidal resonator was proposed based on amplitude characteristic of electrical band-stopfilter. At first approach the analytical model can be considered as valid for practical silencing systems design calculations in ducted systems.

PL

W niniejszym artykule dokonano porównania charakterystyk tłumienia przenoszenia rezonatora helikoidalnego uzyskanych na drodze obliczeń analitycznych i numerycznych. Zaproponowana została zastępcza funkcja transmitancji rezonatora helikoidalnego na podstawie charakterystyki amplitudowej elektrycznego filtru pasmowo-zaporowego. Tak wykonany analityczny model transmitancji w pierwszym przybliżeniu może być uznany za poprawny dla celów obliczeniowych praktycznego projektowania systemów wyciszeniowych w instalacjach kanałowych.

2

Insertion Loss of Spiral Ducts - Measurements and Computations

Łapka W.

Archives of Acoustics

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2009

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Vol. 34, No. 4

537-545

EN

This work presents measured and computed characteristics of insertion loss (IL) of spiral ducts. Numerical and experimental models of spiral ducts have been investigated. For the numerical modeling, a three dimensional model computed by the use of a finite element method in a COMSOL Multiphysics computer application has been used. For the experimental modeling, there has been made a spiral duct model by using a three dimensional rapid prototyping technique. An acoustic system with a round silencer has been ivestigated, and the spiral duct has been inserted at the inlet. IL is considered in this paper as the difference between the sound pressure level (SPL) [dB] probed at only one outlet point of the acoustic system without and with an acoustical filter (spiral duct), respectively. The results of measured and computed IL of spiral ducts presented in this paper confirm the fact that this newly discovered technical solution for attenuating sound in ducted systems has an applicable potential. There are visible small discrepancies between the measurements and computations. The results can differ due to the non ideal dimensions of the experimental model and the non ideal inlet and outlet surroundings of the experimental acoustic system. However, the IL characteristics of the computed model is almost wholly covered by the IL characteristics of the measured model.

3

Acoustic attenuation performance of Helmholtz resonator and spiral duct

Łapka W., Cempel C.

Vibrations in Physical Systems

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2008

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Vol. 23

247--252

EN

This work examines a comparison of acoustic attenuation performance of well known Helmholtz resonator and spiral element inserted into circular duct, which creates spiral duct. The paper consists results of numerical computations by the use of Finite Element Method. Here the spiral is a kind of resonant element, which can be applied in circular ducts, mainly for low speed velocity ducts e.g. ventilation, air-conditioning and heat systems. Results are presented as a transmission loss. The sound attenuation performances of Helmholtz resonator and spiral duct depend on their geometrical relationships. The most important observation is that the sound attenuation in both solutions are based on similar phisical phenomenon – resonance.

4

Noise Reduction of Spiral Ducts

Łapka W., Cempel C.

International Journal of Occupational Safety and Ergonomics

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2007

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Vol. 13, No. 4

419--426

EN

The paper presents noise reduction (NR) of spiral ducts as a result of computational modeling of acoustic wave propagation. Three-dimensional models were created with the finite element method in COMSOL Multiphysics version 3.3. Nine models of spiral ducts with 1–9 spiral leads were considered. Time-harmonic analysis was used to predict NR, which was shown in spectral and interval frequency bands. Spiral duct performance can be seen as a comparison of NR before and after a change from a circular to a spiral duct.