Broadband low-frequency noise reduction using Helmholtz resonator-based metamaterial

2021 ◽  
Vol 69 (4) ◽  
pp. 351-363
Author(s):  
Jhalu Gorain ◽  
Chandramouli Padmanabhan
Keyword(s):  
Transmission Loss ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Broadband Noise ◽  
Unit Cell ◽  
Frequency Noise ◽  
Noise Attenuation ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Pu Foam

Achieving broadband noise attenuation at low frequencies is still a significant challenge. Helmholtz resonators offer good low-frequency noise attenuation but are effective only over a narrow band; the cavity volume required at these frequencies is also larger. This article proposes a new broadband acoustic metamaterial (AMM) absorber, which uses polyurethane (PU) foam embedded with small-size resonators tuned to different frequencies. The AMM design is achieved in three phases: (1) develop a transfer-matrix-based one-dimensionalmodel for a resonator with intruded neck; (2) use this model to develop a novel band broadeningmethod, to select appropriate resonators tuned to different frequencies; and (3) construct a unit cell metamaterial embedded with an array of resonators into PU foam. A small-size resonator tuned to 415 Hz is modified, by varying the intrusion lengths of the neck, to achieve natural frequencies ranging from 210 to 415 Hz. Using the band broadening methodology, 1 unit cell metamaterial is constructed; its effectiveness is demonstrated by testing in an acoustic impedance tube. The broadband attenuation characteristics of the constructed unit cell metamaterial are shown to match well with the predicted results. To demonstrate further the effectiveness of the idea, a metamaterial is formed using 4 periodic unit cells and is tested in a twin room reverberation chamber. The transmission loss is shown to improve significantly, at low frequencies, due to the inclusion of the resonators.

Multi-tonal low frequency noise control using Helmholtz resonators with complex cavity designs for aircraft cabin noise improvement

2021 ◽  
Vol 263 (2) ◽  
pp. 3975-3986
Author(s):  
Tenon Charly Kone ◽  
Sebastian Ghinet ◽  
Raymond Panneton ◽  
Thomas Dupont ◽  
Anant Grewal
Keyword(s):  
Noise Control ◽  
Transmission Loss ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Helmholtz Resonators ◽  
Resonance Frequencies

The noise control at multiple tonal frequencies simultaneously, in the low frequency range, is a challenge for aerospace, ground transportation and building industries. In the past few decades, various low frequency noise control solutions based on acoustic metamaterial designs have been presented in the literature. These solutions showed promising performance and are considered a better alternative to conventional sound insulation materials. In the present investigation, it was noticed that subdividing the cavity of a Helmholtz resonator allowed the control of multi-tonal noise at several resonance frequencies simultaneously and a shift of the resonance peaks towards the low frequencies. This paper proposes concepts of Helmholtz resonators with subdivided cavities to improve the sound transmission loss (STL) performance and simultaneously control the noise at several tonal frequencies. HRs with cylindrical shaped cavities were embedded in a layer of porous material. The STL of the metamaterial noise insulation configuration was predicted using serial and parallel assemblies of transfer matrices (TMM) incorporating a thermo-viscous-acoustic approach to accurately account for the viscous and thermal losses of acoustic wave propagation within the metamaterial. The STL calculated using the proposed TMM approach were observed to be in excellent agreement with the finite element method (FEM) numerical results.

scholarly journals Development of a Slit-Type Soundproof Panel for a Reduction in Wind Load and Low-Frequency Noise with Helmholtz Resonators

2021 ◽  
Vol 11 (18) ◽  
pp. 8678
Author(s):  
Byunghui Kim ◽  
Seokho Kim ◽  
Yejin Park ◽  
Marinus Mieremet ◽  
Heungguen Yang ◽  
...  
Keyword(s):  
Transmission Loss ◽  
Numerical Study ◽  
Shape Change ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Wind Load ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Helmholtz Resonators ◽  
Commercial Program

With the rapid increase in automobiles, the importance of reducing low-frequency noise is being emphasized for a comfortable urban environment. Helmholtz resonators are widely used to attenuate low-frequency noise over a narrow range. In this study, a slit-type soundproof panel is designed to achieve low-frequency noise attenuation in the range of 500 Hz to 1000 Hz with the characteristics of a Helmholtz resonator and the ability to pass air through the slits on the panel surface for reducing wind load. The basic dimension of the soundproof panel is determined using the classical formula and numerical analysis using a commercial program, COMSOL Multiphysics, for transmission loss prediction. From the numerical study, it is identified that the transmission loss performance is improved compared to the basic design according to the shape change and configuration method of the Helmholtz resonator. Although the correlation according to the shape change and configuration method cannot be derived, it is confirmed that it can be used as an effective method for deriving a soundproof panel design that satisfies the basic performance.

Low Frequency Noise Annoyance Assessment by Low Frequency Noise Rating (LFNR) Curves

1983 ◽  
Vol 2 (1) ◽  
pp. 20-28 ◽  
Author(s):  
N. Broner ◽  
H.G. Leventhall
Keyword(s):  
Laboratory Experiments ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Noise Annoyance

Over recent years, it has become apparent that low frequency noise annoyance is more widespread than originally believed. Annoyance has occurred where the emitted noise is unbalanced towards the low frequencies even though the dB(A) level has been low. Following laboratory experiments carried out as part of an investigation into low frequency annoyance, combined with field annoyance data, the Low Frequency Noise Rating (LFNR) curves are proposed for the assessment of low frequency noise annoyance complaints.

scholarly journals SeMSA: a compact super absorber optimised for broadband, low-frequency noise attenuation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Andrew McKay ◽  
Ian Davis ◽  
Jack Killeen ◽  
Gareth J. Bennett
Keyword(s):  
New Technology ◽  
Perforated Plate ◽  
Low Frequency ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Noise Attenuation ◽  
Loss Mechanism ◽  
Small Form Factor ◽  
Broadband Sound ◽  
Sub Wavelength

Abstract The attenuation of low-frequency broadband noise in a light, small form-factor is an intractable challenge. In this paper, a new technology is presented which employs the highly efficient visco-thermal loss mechanism of a micro-perforated plate (MPP) and successfully lowers its frequency response by combining it with decorated membrane resonators (DMR). Absorption comes from the membranes but primarily from the MPP, as the motion of the two membranes causes a pressure differential across the MPP creating airflow through the perforations. This combination of DMR and MPP has led to the Segmented Membrane Sound Absorber (SeMSA) design, which is extremely effective at low-frequency broadband sound absorption and which can achieve this at deep sub-wavelength thicknesses. The technology is compared to other absorbers to be found in the literature and the SeMSA outperforms them all in either the 20–1000 Hz or 20–1200 Hz range for depths of up to 120 mm. This was verified through analytical, finite element and experimental analyses.

scholarly journals Does Low Frequency Noise at Modarate Levels Influence Human Mental Performance?

2005 ◽  
Vol 24 (1) ◽  
pp. 25-42 ◽  
Author(s):  
Malgorzata Pawlaczyk-łuszczyńska ◽  
Adam Dudarewicz ◽  
Małgorzata Waszkowska ◽  
Wiesław Szymczak ◽  
Maria Kameduła ◽  
...  
Keyword(s):  
Low Frequency ◽  
Well Being ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Subjective Well Being ◽  
Low Frequency Noise ◽  
Mental Performance ◽  
Reasoning Test ◽  
Math Reasoning ◽  
Exposure Conditions

The aim of this study was to assess the influence of low frequency noise (LFN) at levels normally occurring in the industrial control rooms on human mental performance (attention, visual perception and logical reasoning) and subjective well-being. Subjects were 191 male volunteers categorised in terms of subjective sensitivity to noise in general. They performed standardised tests: the Signal Detection Test (test I), the Stroop Colour-Word Test (test II), and two sub-tests of the General Aptitude Test Battery, i.e. the Math Reasoning Test (test III) and the Comparing of Names Test (test IV). Three different acoustic conditions were used in the between-subjects design: the background laboratory noise of about 30 dB(A), LFN, and a broadband noise without dominant low frequency components (reference noise) at 50 dB(A). Each subject was tested only once in random-assigned exposure conditions. Generally, no significant differences in performance related to exposure conditions were noted. Some of the results from test I and test II were influenced by sensitivity to noise. However, there were no significant differences between high- and low-sensitive subjects during exposure to LFN. The annoyance of LFN and reference noise was rated higher than that of the background noise. Subjects highly-sensitive to noise reported higher annoyance due to LFN in comparison with low-sensitives. No significant differences related to noise sensitivity in annoyance assessment of background and reference noises were noted. In conclusion, no effects due to LFN on mental performance compared to background and reference noises were found.

scholarly journals Factors influencing low-frequency noise reduction in typical Chinese dwelling layouts

2020 ◽  
pp. 146134842094297
Author(s):  
Yang Song ◽  
Jian Kang
Keyword(s):  
Noise Reduction ◽  
Noise Exposure ◽  
Noise Source ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Factors Influencing ◽  
Polyline Distance

Existing approaches to reducing the low-frequency noise exposure of dwellings are not always sufficient. This study investigated the significance of dwelling layout design for low-frequency noise control. The sound distribution in six typical Chinese dwelling layouts was analysed using in-situ measurements under steady-state noise of various low frequencies. The results showed that among two-bedroom dwelling layouts, the overall average noise reduction varied considerably (6 dB). The noise reduction for room levels (number of rooms sound crosses) 1–2 and 2–3 varies by 5 and 3 dB, respectively, and the noise reduction at door openings varies by 5 dB. A model to approximate the low-frequency noise reduction of a layout was developed using the polyline distance from the noise source and the number of walls the polyline has to cross, which were clearly shown to influence low-frequency noise reduction and seem to be the strongest investigated factors.

Attenuation of Earmuffs against Low Frequency Noise

1987 ◽  
Vol 6 (4) ◽  
pp. 167-174 ◽  
Author(s):  
Jukka Starck ◽  
Jussi Pekkarinen ◽  
Seppo Aatola
Keyword(s):  
Low Frequency ◽  
Peak Level ◽  
Standard Test ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Hearing Protectors ◽  
Noise Measurements ◽  
Attenuation Values ◽  
Very High

The standard test for hearing protectors cannot be applied to determine the attenuation values for low frequency noise or for noise consisting of high intensity impulses. Moreover, the aging of earmuffs and the use of spectacles may cause leakage which decreases attenuation mainly at low frequencies. To study the real attenuation of earmuffs, noise measurements were taken outside and inside the earmuffs of workers at industrial work places, and of military conscripts when shooting with different firearms. The effect of spectacles on the attenuation was measured under laboratory conditions. In industrial workplaces the average attenuation was 4 dB in the 63 and 125 Hz octave bands. For shooting noise the attenuation was found to be good for small calibre weapons but poor for large calibre weapons, which generate very high peak level impulses at low frequencies. Spectacles decreased earmuff attenuation by 9–11 dB.

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