Low-Frequency Acoustic Absorption of 3D Printed Cylinders

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Paul E. Slaboch ◽  
Sophie Kaye ◽  
Ethan Casavant
Keyword(s):  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Outer Diameter ◽  
Acoustic Absorption ◽  
Large Space ◽  
Low Frequencies ◽  
Cylinder Length ◽  
3D Printed ◽  
Hollow Cylinders

Abstract Attenuating low-frequency sound is often problematic, due to the large space required for common absorptive materials to mitigate such noise. However, natural hollow reeds are known to effectively attenuate low frequencies while occupying relatively little space compared to traditional absorptive materials. The present study determines the effect of varied outer diameter and outer spacing on the 200–1600 Hz acoustic absorption of 3D printed arrays of hollow cylinders. Samples were tested in a 100-mm diameter normal incidence impedance tube such that cylinder length was oriented perpendicular to the incoming plane wave. By varying only one geometric element of each array, the absorption due to any parameter can be assessed individually. It was found that minimizing cylinder spacing and maximizing cylinder diameter resulted in increased overall absorption and produced more focused absorption peaks at specific low frequencies. Wider cylinder spacing produced a broader absorptive frequency range, despite shifting upward in frequency. Thus, manipulating these variables can specifically target absorption for low-frequency noise that would otherwise disturb listeners.

Low Frequency Absorption of Additively Manufactured Cylinders

2019 ◽  
Author(s):  
Sophie R. Kaye ◽  
Ethan D. Casavant ◽  
Paul E. Slaboch
Keyword(s):  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Outer Diameter ◽  
Acoustic Absorption ◽  
Frequency Range ◽  
Large Space ◽  
Low Frequencies ◽  
Cylinder Length ◽  
Hollow Cylinders

Abstract Attenuating low frequencies is often problematic, due to the large space required for common absorptive materials to mitigate such noise. However, natural hollow reeds are known to effectively attenuate low frequencies while occupying relatively little space compared to traditional absorptive materials. This paper discusses the effect of varied outer diameter, and outer spacing on the 200–1600 Hz acoustic absorption of additively manufactured arrays of hollow cylinders. Samples were tested in a 10 cm diameter normal incidence impedance tube such that cylinder length was oriented perpendicular to the incoming plane wave. By varying only one geometric element of each array, the absorption due to any particular parameter can be assessed individually. The tests confirmed the hypothesis that minimizing cylinder spacing and maximizing cylinder diameter resulted in increased overall absorption and produced more focused absorption peaks at specific low frequencies. Wider cylinder spacing produced a broader absorptive frequency range, despite shifting upward in frequency. Thus, manipulating these variables can specifically target absorption for low frequency noise that would otherwise disturb listeners.

3D printed multifunctional, load-bearing, low-frequency sound absorbers

2021 ◽  
Vol 263 (1) ◽  
pp. 5605-5610
Author(s):  
William Johnston ◽  
Pulitha Godakawela Kankanamalage ◽  
Bhisham Sharma
Keyword(s):  
Mechanical Performance ◽  
Low Frequency ◽  
Normal Incidence ◽  
Acoustic Properties ◽  
Low Frequencies ◽  
Load Bearing ◽  
Fibrous Network ◽  
Size Limitation ◽  
Porous Architecture ◽  
3D Printed

Cellular porous materials are an attractive choice for lightweight structural design. However, though their open porous architecture is ideally suited for multifunctional applications, their use is typically limited by the pore sizes achievable by traditional as well as advanced fabrication processes. Here, we present an alternative route towards overcoming this pore size limitation by leveraging our recent success in printing fibrous structures. This is achieved by superimposing a fibrous network on a load-bearing, open-celled porous architecture. The multifunctional structure is 3D printed using a novel technique that enables us to simultaneously print a load-bearing scaffold and the necessary fibrous network. The acoustic properties of the printed structures are tested using a normal-incidence impedance tube method. Our results show that such structures can provide very high absorption at low frequencies while retaining the mechanical performance of the underlying architected structure.

scholarly journals On articulated plates with micro-slits to tackle low-frequency noise

Acta Acustica ◽  
2021 ◽  
Vol 5 ◽  
pp. 31
Author(s):  
Massimo Emiliano D’Elia ◽  
Thomas Humbert ◽  
Yves Aurégan
Keyword(s):  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Correct Identification ◽  
Low Frequency Noise ◽  
Perfect Absorption ◽  
Flow Measurements ◽  
Low Frequencies ◽  
Acoustic Liner ◽  
Acoustic Treatment

In recent years, new concepts of acoustic absorbers dedicated to the reduction of low-frequency noise have been developed. Among them, liners with moving parts, such as membrane-based liners, have been an object of particular interest. In the present paper, we propose a liner concept based on a cantilever beam made of articulated plates with micro-slits. Compared to membrane technologies, these micro-slits introduce a small leakage from the backing cavity that reduces the high compressibility effects occurring at very low frequencies in a small cavity. An acoustic liner including an ensemble of such articulated plates has been fabricated and characterized for grazing acoustic incidence in absence and in presence of flow. Measurements in an impedance tube at normal incidence have also been performed, and perfect absorption is obtained at a frequency where the liner thickness corresponds to 1/16th of the acoustic wavelength. A new and simple model is proposed to predict the attenuation of this type of acoustic treatment. The results are in good agreement with the measurements, indicating a correct identification of the physical phenomena here at stake.

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.

Low-frequency noise control using layered granular aerogel and limp porous media

2021 ◽  
Vol 263 (4) ◽  
pp. 2724-2729
Author(s):  
Yutong Xue ◽  
Amrutha Dasyam ◽  
J. Stuart Bolton ◽  
Bhisham Sharma
Keyword(s):  
Noise Control ◽  
Glass Fibers ◽  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Fibrous Materials ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Fibrous Media ◽  
Impedance Tube Method

The acoustic absorption of granular aerogel layers with a granule sizes in the range of 2 to 40 μm is dominated by narrow-banded, high absorption regions in the low-frequency range and by reduced absorption values at higher frequencies. In this paper, we investigate the possibility of developing new, low-frequency noise reduction materials by layering granular aerogels with traditional porous sound absorbing materials such as glass fibers. The acoustic behavior of the layered configurations is predicted using the arbitrary coefficient method, wherein the granular aerogel layers are modeled as an equivalent poro-elastic material while the fibrous media and membrane are modeled as limp media. The analytical predictions are verified using experimental measurements conducted using the normal incidence, two-microphone impedance tube method. Our results show that layered configurations including granular aerogels, fibrous materials, and limp membranes provide enhanced sound absorption properties that can be tuned for specific noise control applications over a broad frequency range.

scholarly journals Noise Characterization of Vortex-State GMR Sensors with Different Free Layer Thicknesses

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 1013
Author(s):  
Herbert Weitensfelder ◽  
Hubert Brueckl ◽  
Armin Satz ◽  
Dieter Suess
Keyword(s):  
Spin Valve ◽  
Low Frequency ◽  
Vortex State ◽  
Frequency Noise ◽  
Free Layer ◽  
Low Frequencies ◽  
Gmr Sensors ◽  
Noise Characterization ◽  
Higher Sensitivity

The spin valve principle is the most prominent sensor design among giant- (GMR) and tunneling (TMR) magnetoresistive sensors. A new sensor concept with a disk shaped free layer enables the formation of a flux-closed vortex magnetization state if a certain relation of thickness to diameter is given. The low frequency noise of current-in-plane GMR sensing elements with different free layer thicknesses at different external field strengths has been measured. The measurements of the 1/f noise in external fields enabled a separation of magnetic and electric noise contributions. It has been shown that while the sensitivity is increasing with a decreasing element thickness, the pink noise contribution is increasing too. Still the detection limit at low frequencies is better in thinner free layer elements due to the higher sensitivity.

Inadequate Standards Currently Applied by Local Authorities to Determine Statutory Nuisance from LF and Infrasound

2003 ◽  
Vol 22 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Hazel Guest
Keyword(s):  
Local Authority ◽  
Low Frequency ◽  
Measurement Information ◽  
Frequency Noise ◽  
Local Authorities ◽  
Low Frequencies ◽  
Specific Effects ◽  
Basic Understanding

Knowledge of the latest results in Low Frequency Noise (LFN) and infrasound research are not being transmitted, either to government whose job it is to legislate on standards of noise and vibration, or to local authority officers whose job it is to look into complaints and enforce standards. The dismissal of complaints is frequently based on inappropriate techniques such as the application of A-weighting, a lack of understanding of vibration transmission including building resonance, and a lack of basic understanding about the perception of low frequencies by complainants, for instance the lowering of the lower audibility threshold arising from exposure. This paper asks those involved in research to ensure that their relevant findings are more widely disseminated, along with advice to legislators and local authorities on measurement, information on LF and infrasound resonance in buildings, recommendations for appropriate standards to be used in assessing LF and infrasound as a Statutory Nuisance, and information about the effects of long-term exposure. There is a need for more research in situ into specific effects.

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.

scholarly journals Active Structural Acoustic Control of an Active Casing Placed in a Corner

2019 ◽  
Vol 9 (6) ◽  
pp. 1059 ◽  
Author(s):  
Anna Chraponska ◽  
Stanislaw Wrona ◽  
Jaroslaw Rzepecki ◽  
Krzysztof Mazur ◽  
Marek Pawelczyk
Keyword(s):  
Active Noise Control ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Emission ◽  
Sound Sources ◽  
Low Frequencies ◽  
Emission Efficiency ◽  
Active Noise ◽  
Acoustic Control ◽  
Device Noise

Electric appliances used in workplaces and everyday life often generate a low-frequency noise, which affects human body systems. Passive methods employed to reduce noise are not effective at low frequencies. The classical approach to active noise control practically involves the generation of local zones of quiet, whereas at other areas the noise is reinforced. Moreover, it usually requires a large number of secondary sound sources. Hence, an active casing approach has been developed. The active casing panels’ vibrations are controlled to reduce the device noise emission. Efficiency of this method has been previously confirmed by the authors and the results have been reported in multiple journal publications. However, in the previous research experiments, the active casing was placed at a distance from the enclosure walls. In this research, the active casing is located in a corner and such placement is intentionally used to facilitate the active control system’s operation. The noise reduction performance is investigated at multiple configurations, including a range of distances from the corner and different error microphone arrangements. The analysis of both primary and secondary paths is given. Advantages and drawbacks of different active casing configurations are presented and discussed.

Sign in / Sign up

Export Citation Format

Share Document