Novel method of sound barrier measurement of porous and nonporous materials

2013 ◽  
Vol 10 (4) ◽  
pp. 353-358 ◽  
Author(s):  
Vijay Baheti ◽  
V. Kothari
Keyword(s):  
Composite Structures ◽  
Simple Technique ◽  
Field Measurements ◽  
Woven Fabric ◽  
Sound Waves ◽  
Sound Barrier ◽  
Actual Field ◽  
Novel Method ◽  
Larger Sample ◽  
Random Scatter

Noise is an unwanted sound which creates the pollution and adverse effects on individual. One of the simple ways to reduce the noise is to place the acoustic material in the path between the source and the receiver so that sound waves get either absorbed or blocked while reaching towards the receiver. There are various techniques available to measure sound absorption or sound barrier (blocking) caused by the acoustic material. However these techniques are also associated with certain limitations. Our objective was to design and fabricate simple technique to measure sound barrier which overcomes these limitations and allows larger sample size and random scatter of sound wave to accurately predict actual field measurements. A sound source (i.e. a speaker) and a microphone, placed in different pipes separated by sample in between, were used for the measurement of sound barrier property of porous materials (nonwovens, woven fabric, and foam), nonporous materials (rubber, cardboard) and their composite structures at four different frequencies 250 Hz, 500 Hz, 1,000 Hz, and 2000 Hz. Different set of readings were taken in absence and presence of the sample by measuring the transmitted sound across the sample.

scholarly journals Bilayer ventilated labyrinthine metasurfaces with high sound absorption and tunable bandwidth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiayuan Du ◽  
Yuezhou Luo ◽  
Xinyu Zhao ◽  
Xiaodong Sun ◽  
Yanan Song ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Air Flow ◽  
Single Layer ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Sound Barrier ◽  
Free Air ◽  
Relative Bandwidth ◽  
Wide Range ◽  
High Sound

AbstractThe recent advent of acoustic metamaterials offers unprecedented opportunities for sound controlling in various occasions, whereas it remains a challenge to attain broadband high sound absorption and free air flow simultaneously. Here, we demonstrated, both theoretically and experimentally, that this problem can be overcome by using a bilayer ventilated labyrinthine metasurface. By altering the spacing between two constituent single-layer metasurfaces and adopting asymmetric losses in them, near-perfect (98.6%) absorption is achieved at resonant frequency for sound waves incident from the front. The relative bandwidth of absorption peak can be tuned in a wide range (from 12% to 80%) by adjusting the open area ratio of the structure. For sound waves from the back, the bilayer metasurface still serves as a sound barrier with low transmission. Our results present a strategy to realize high sound absorption and free air flow simultaneously, and could find applications in building acoustics and noise remediation.

scholarly journals Spiral Sound Wave Transducer Based on the Longitudinal Vibration

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3674 ◽  
Author(s):  
Wei Lu ◽  
Yu Lan ◽  
Rongzhen Guo ◽  
Qicheng Zhang ◽  
Shichang Li ◽  
...  
Keyword(s):  
Sound Wave ◽  
Longitudinal Vibration ◽  
Three Dimensional ◽  
Low Frequency ◽  
Sound Field ◽  
Field Measurements ◽  
Sound Waves ◽  
Underwater Sound ◽  
Three Dimensional Finite Element ◽  
Wave Transducer

A spiral sound wave transducer comprised of longitudinal vibrating elements has been proposed. This transducer was made from eight uniform radial distributed longitudinal vibrating elements, which could effectively generate low frequency underwater acoustic spiral waves. We discuss the production theory of spiral sound waves, which could be synthesized by two orthogonal acoustic dipoles with a phase difference of 90 degrees. The excitation voltage distribution of the transducer for emitting a spiral sound wave and the measurement method for the transducer is given. Three-dimensional finite element modeling (FEM)of the transducer was established for simulating the vibration modes and the acoustic characteristics of the transducers. Further, we fabricated a spiral sound wave transducer based on our design and simulations. It was found that the resonance frequency of the transducer was 10.8 kHz and that the transmitting voltage resonance was 140.5 dB. The underwater sound field measurements demonstrate that our designed transducer based on the longitudinal elements could successfully generate spiral sound waves.

scholarly journals The Effect of String Tension Variation on the Perceived Pitch of a Classical Guitar

2014 ◽  
Vol 2 (1) ◽  
pp. 53-81
Author(s):  
Wanda Jadwiga Lewis ◽  
James Raphael Smith ◽  
Wanda J. Lewis ◽  
James R. Smith
Keyword(s):  
Classical Theory ◽  
Fundamental Mode ◽  
String Tension ◽  
Classical Guitar ◽  
Sound Waves ◽  
Single Wave ◽  
Geometric Stiffness ◽  
Vibrating String ◽  
Novel Method ◽  
Method Of Assessment

Actual motion of a vibrating guitar string is a superposition of many possible shapes (modes) in which it could vibrate. Each of these modes has a corresponding frequency, and the lowest frequency is associated with a shape idealised as a single wave, referred to as the fundamental mode. The other contributing modes, each with their own progressively higher frequency, are referred to as overtones, or harmonics. By attaching a string to a medium (a soundboard) capable of a response to the vibrating string, sound waves are generated. The sound heard is dominated by the fundamental mode, ‘coloured’ by contributions from the overtones, as explained by the classical theory of vibration. The classical theory, however, assumes that the string tension remains constant during vibration, and this cannot be strictly true; when considering just the fundamental mode, string tension will reach two maximum changes, as it oscillates up and down. These changes, occurring twice during the fundamental period match the frequency of the octave higher, 1st overtone. It is therefore plausible to think that the changing tension effect, through increased force on the bridge and, therefore, greater soundboard deflection, could be amplifying the colouring effect of (at least) the 1st overtone.In this paper, we examine the possible influence of string tension variation on tonal response of a classical guitar. We use a perturbation model based on the classical result for a string in general vibration in conjunction with a novel method of assessment of plucking force that incorporates the engineering concept of geometric stiffness, to assess the magnitude of the normal force exerted by the string on the bridge. The results of our model show that the effect of tension variation is significantly smaller than that due to the installed initial static tension, and affects predominantly the force contribution arising from the fundamental mode. We, therefore, conclude that string tension variation does not contribute significantly to tonal response. Photo credit: By Biblola (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Effect of Mechanical Properties on Various Surface Treatment Processes of Banana/Cotton Woven Fabric Vinyl Ester Composite

2017 ◽  
Vol 867 ◽  
pp. 41-47 ◽  
Author(s):  
Chitra Umachitra ◽  
N.K. Palaniswamy ◽  
O.L. Shanmugasundaram ◽  
P.S. Sampath
Keyword(s):  
Mechanical Properties ◽  
Composite Structures ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Surface Treatments ◽  
Fiber Reinforced Polymer ◽  
Woven Fabric ◽  
Fiber Reinforced ◽  
Reinforced Polymer ◽  
Structural Applications

Natural fibers have been used to reinforce materials in many composite structures. Many types of natural fibers have been investigated including flax, hemp, ramie, sisal, abaca, banana etc., due to the advantage that they are light weight, renewable resources and have marketing appeal. These agricultural wastes can also be used to prepare fiber reinforced polymer hybrid composites in various combinations for commercial use. Application of composite materials in structural applications has presented the need for the engineering analysis. The present work focuses on the fabrication of polymer matrix composites by using natural fibers like banana and cotton which are abundant in nature and analysing the effect of mechanical properties of the composites on different surface treatments on the fabric. The effect of various surface treatments (NaOH, SLS, KMnO4) on the mechanical properties namely tensile, flexural and impact was analyzed and are discussed in this project. Analysing the material characteristics of the compression moulded composites; their results were measured on sections of the material to make use of the natural fiber reinforced polymer composite material for automotive seat shell manufacturing.

Research of Different Noise Barriers Efficiency at Different Temperature

2017 ◽  
Author(s):  
Tomas Vilniškis ◽  
Tomas Januševicius
Keyword(s):  
Air Temperature ◽  
Noise Level ◽  
Structural Changes ◽  
Field Measurements ◽  
Sound Waves ◽  
Noise Barriers ◽  
Different Temperatures ◽  
Noise Measurements ◽  
Noise Barrier ◽  
Key Aspects

In this article was analyzed acoustic efficiency of two different construction noise barriers. Field measurements of noise tests were carried out before and behind a wooden barrier, which height was 2.9 meters and a wooden wall with equipped roof, which height was 3.2 m. As is known the length of the wall, height, surface roughness, shape and material of the wall – key aspects of determining the effectiveness of noise barrier. Different materials, depending on their characteristics of the hard or soft, porous or dense, interact differently with the sound of waves. Article contains research results of noise measurements at positive and negative air temperature. There analyzing wooden noise barrier acoustic efficiency at different temperatures and the effects of temperature to the diffraction of sound waves through the peak of the barrier. Test results show, that noise barrier without structural changes reduced noise level to 14–22 dB, noise barrier with structural changes reduced noise level to 20–23,1 dB, when air temperature was positive. When air temperature was negative, noise barrier without structural changes reduced noise level to 15,5–21,4 dB, noise level with structural changes to 19–26,6 dB.

scholarly journals Bending Properties of 3D Glass Woven Fabric Reinforced Composites

1993 ◽  
Vol 2 (4) ◽  
pp. 096369359300200
Author(s):  
Hiroyuki Hamada ◽  
Akihiro Fujita ◽  
Zenichiro Maekawa ◽  
Masaya Kotaki
Keyword(s):  
Composite Structure ◽  
Composite Beam ◽  
Composite Structures ◽  
Large Scale ◽  
Hybrid Composites ◽  
Woven Fabric ◽  
Light Weight ◽  
Reinforced Composites ◽  
Bending Properties ◽  
Chopped Strand Mat

3D glass woven fabric (PARABEAM) reinforced composites are of particular interest to composite industry, because light weight large scale composite structures can be fabricated. Bending properties of hybrid composites with 3D fabric and chopped strand mat were possible to be estimated by using theory of composite beam. The relations between thickness, weight and bending properties of the 3D composites could be drawn for designing composite structure.

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