Narrowband Noise Attenuation Characteristics of in-Duct Acoustic Screens

Rim, Minhong; Kim, Yang-Hann

doi:10.1006/jsvi.1999.2898

Cited by 8 publications

(3 citation statements)

References 9 publications

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“…Tis is especially true when the compressor is located indoors, where complaints about low-frequency compressor noise are more prevalent. Investigations of the noise attenuation characteristics reveal that, at the same distance, lowfrequency noise attenuates less than high-frequency noise [27]. Terefore, researchers should give special consideration to the low-frequency noise generated by the indoor unit compressor in this particular structural design of air conditioners.…”

Section: The Noise Problem Of the New Split Air Conditionermentioning

confidence: 99%

An Investigation of the Acoustic Enclosure of an Air Conditioning Compressor Using Response Surface Analysis and Topological Rigidity Optimization

Cao,

Yang,

et al. 2024

Shock and Vibration

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A novel split-type air conditioning system is introduced to balance usability and portability. Unlike conventional split-type systems, where the compressor is typically placed outside, this system situates the compressor within the indoor unit, which may expose users to compressor noise. There are prominent peaks in the compressor noise spectrum, particularly at the compressor operating frequency and its harmonics, notably the second and third harmonics. The research presents a multilayered acoustic enclosure specifically designed for air conditioning compressors to address this issue without modifying the compressor or indoor unit casing. In order to get better sound insulation performance, a response surface methodology (RSM) is applied to optimize the thickness ratio, open area ratio, and open area height of the acoustic enclosure with predefined thickness. In addition, topological optimization is employed to strengthen weak areas of the acoustic enclosure. Then, experimental trials using the proposed acoustic enclosure are conducted in a semianechoic chamber. Results demonstrate significant reductions in noise levels, including 7.99 dB(A), 5.69 dB(A), and 5.19 dB(A) reductions in the fundamental frequency, second harmonic, and third harmonic noise of the compressor’s operating frequency, respectively.

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Section: The Noise Problem Of the New Split Air Conditionermentioning

confidence: 99%

An Investigation of the Acoustic Enclosure of an Air Conditioning Compressor Using Response Surface Analysis and Topological Rigidity Optimization

Cao,

Yang,

et al. 2024

Shock and Vibration

View full text Add to dashboard Cite

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“…Previous studies have reported that asymmetric acoustic design can be tactfully used to achieve noise attenuation. For example, the insertion of an acoustic screen can divide the acoustic path into two asymmetric tunnels, which give rise to a large sound attenuation in a narrow-band content [ 10 ]. The specially designed asymmetric inlet and outlet configurations for acoustic silencers could effectively improve the transmission loss [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

A Structure Design Method for Reduction of MRI Acoustic Noise

Nan

Zong

Chen

et al. 2017

Computational and Mathematical Methods in Medicine

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The acoustic problem of the split gradient coil is one challenge in a Magnetic Resonance Imaging and Linear Accelerator (MRI-LINAC) system. In this paper, we aimed to develop a scheme to reduce the acoustic noise of the split gradient coil. First, a split gradient assembly with an asymmetric configuration was designed to avoid vibration in same resonant modes for the two assembly cylinders. Next, the outer ends of the split main magnet were constructed using horn structures, which can distribute the acoustic field away from patient region. Finally, a finite element method (FEM) was used to quantitatively evaluate the effectiveness of the above acoustic noise reduction scheme. Simulation results found that the noise could be maximally reduced by 6.9 dB and 5.6 dB inside and outside the central gap of the split MRI system, respectively, by increasing the length of one gradient assembly cylinder by 20 cm. The optimized horn length was observed to be 55 cm, which could reduce noise by up to 7.4 dB and 5.4 dB inside and outside the central gap, respectively. The proposed design could effectively reduce the acoustic noise without any influence on the application of other noise reduction methods.

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“…Rim and Kim [8], for instance, analysed experimentally and analytically the attenuation produced by acoustic screens inside a rectangular ventilation duct. Our work follows a similar principle and sets out to simulate the sound wave propagation inside a duct where the sound attenuation is provided by thin elements working as screens to counter sound propagation.…”

Section: Introductionmentioning

confidence: 99%

Using a Dual-BEM formulation to model the sound pressure wavefield provided by absorbing thin screens attached to the walls of a duct

António

Godinho

Amado-Mendes

et al. 2012

WIT Transactions on Modelling and Simulation

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The modelling of the 2D sound pressure wavefield in the presence of thin absorbing screens attached to the walls of a duct, assumed to be infinitely long, is described in this paper. The simulation uses a frequency-domain Dual-BEM (BEM/TBEM) formulation, which overcomes the thin-body difficulty that arises with the classical BEM formulation. The sound absorption is simulated by imposing impedance boundary conditions, which are applied in conjunction with a Dual-BEM approach. The fundamental solutions used in the formulation allow the solution to be obtained without discretizing the duct's walls. Thus, only the boundary of each absorbing screen attached to the duct's walls is modelled, which makes the proposed formulation efficient even at high excitation frequencies. The hypersingular integrals that result from the implementation of the TBEM are computed analytically. The formulation is used to compare results obtained with absorbing screens with those obtained with rigid screens and with those obtained in a duct without screens. Results in the time domain are obtained by applying an inverse Fourier transform to the frequency results.

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Narrowband Noise Attenuation Characteristics of in-Duct Acoustic Screens

Cited by 8 publications

References 9 publications

An Investigation of the Acoustic Enclosure of an Air Conditioning Compressor Using Response Surface Analysis and Topological Rigidity Optimization

An Investigation of the Acoustic Enclosure of an Air Conditioning Compressor Using Response Surface Analysis and Topological Rigidity Optimization

A Structure Design Method for Reduction of MRI Acoustic Noise

Using a Dual-BEM formulation to model the sound pressure wavefield provided by absorbing thin screens attached to the walls of a duct

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