Modal filters for mitigation of in-duct sound

Sack, Stefan; Åbom, Mats

doi:10.1121/2.0000473

Cited by 17 publications

(10 citation statements)

References 16 publications

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“…The standard approach to broaden the absorption bandwith [19] of the MPA is to partition its cavity. In Fig.…”

Section: Simulated Mpa Configurationsmentioning

confidence: 99%

“…This is also the basis for the design of more complex geometrical absorber setups. More advanced setups [1,19] are necessary, because the MPA requires a more thoroughly carried out design procedure than the conventional fibrous or foam based absorbers. In the latter case, the material is likely locally-reacting which results in a broadband absorption behavior and most often the cavity length L c is the only required geometrical parameter.…”

Section: Introductionmentioning

confidence: 99%

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Micro-perforated panels for noise reduction

Floss

Czwielong

Becker

2021

Elektrotech. Inftech.

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Space limitations in duct applications, new industrial and health safety regulations require new absorber configurations. Micro-perforated panels (MPP) as used in micro-perforated absorbers (MPA) allow new sound absorber concepts in the category of metamaterials. In this contribution we investigate MPA designs for the low and mid-to-high frequency range and apply finite element (FE) simulations to precisely design absorber configurations for applications in room acoustics and axial fans. The investigations show that the MPA’s cavity configuration must be customized for the desired frequency range and has significant influence on fan performance when applied in a duct flow setup.

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“…The standard approach to broaden the absorption bandwith [19] of the MPA is to partition its cavity. In Fig.…”

Section: Simulated Mpa Configurationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Micro-perforated panels for noise reduction

Floss

Czwielong

Becker

2021

Elektrotech. Inftech.

View full text Add to dashboard Cite

show abstract

“…These offer the advantage that they do not generate any additional pressure loss and can be designed for corresponding frequency-specific absorption levels. These sound absorbers have already been integrated, for example, in the direct proximity of axial fans in ducts, in HVAC systems or in rooms [9][10][11][12][13][14][15][16]. In addition, MPAs offer the properties that they are non-flammable, do not concentrate toxic substances, and do not pose a risk to humans from accumulated viruses or smallest fibers.…”

Section: Introductionmentioning

confidence: 99%

Sound reduction in heat exchanger modules by integrating plate absorbers with sub-millimeter openings

2021

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In air conditioning systems heat exchangers are frequently installed upstream of ventilators. These modules are part of the daily life of humans and should therefore create an environment that is as quiet as possible. The heat exchanger generates increased turbulence, which leads to increased sound emissions of the ventilator. Due to installation space limitations, it is not possible to connect silencers to the heat exchanger module. A novel concept is presented, which allows to reduce the sound emissions of heat exchanger due to plate absorbers without the need of additional installation room. The plates contain sub-millimeter openings. They are integrated into the heat exchanger housing together with back volumes. This arrangement guarantees compactness and generates no additional flow resistance. The emitted sound could be reduced by up to 2.9 dB in the partial load range. The main advantages of the concept presented are individual adjustment, cost-effective design and simple installation.

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“…Allam and Åbom [13] used MPPs as a shroud for the reduction of sound in automotive radiator cooling fans and as splitter type silencers for fan noise control [14]. In [15] Sacks and Åbom introduced modal filters based on MPPs for medium frequency sound absorption of the tonal noise of a compressor. He realized a two-stage duct silencer by applying additional MPPs in a starlike arrangement within a circular shaped duct to specifically dampen higher order spinning modes.…”

Section: Introductionmentioning

confidence: 99%

Design of an in-duct micro-perforated panel absorber for axial fan noise attenuation

2021

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The reduction of fan noise in ducts is a challenging task for acoustic engineers. Usually, the confined space where an absorber can be integrated is small. In addition, one has to consider the influence of the absorber on the flow field and the attenuation of noise should be as great as possible. In this contribution, we investigate the application of a micro-perforated absorber (MPA) in the direct vicinity of a low-pressure axial fan operating at low Mach number conditions. The micro-perforated plates (MPP) are modeled using the Johnson–Champoux–Allard–Lafarge (JCAL) model for porous materials. The entire geometrical setup of duct, fan and MPA is then simulated with the Finite Element (FE) method; the pre-processing effort is reduced by using non-conforming grids to discretize the different regions. The influence of the cavity length and the positioning of the fan are analyzed. The results are then applied to the construction of a full-sized MPA duct component that takes the limited space into consideration. Simulation results and overall functionality are compared to experimental results obtained in an axial-fan test rig. The Finite Element framework proved to be robust in predicting overall sound pressure level reduction in the higher volume flow rates. It is also shown that the MPP increases sound reduction in the low-frequency regime and at two resonant frequencies of the MPA setup. However, its main benefit lies in maintaining the efficiency of the fan. The location of the fan downstream or within the MPA has a significant effect on both the simulated and measured sound reduction.

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Modal filters for mitigation of in-duct sound

Cited by 17 publications

References 16 publications

Micro-perforated panels for noise reduction

Micro-perforated panels for noise reduction

Sound reduction in heat exchanger modules by integrating plate absorbers with sub-millimeter openings

Design of an in-duct micro-perforated panel absorber for axial fan noise attenuation

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