scholarly journals 3106 On the Absorption Characteristic of the Clay Models : Part 1. Measurement of Average Absorption-Coefficient(Environmental Engineering)

1967 ◽  
Vol 42 (0) ◽  
pp. 590
Author(s):  
Tsuyoshi Tokura
Keyword(s):  
Absorption Coefficient ◽  
Environmental Engineering ◽  
Absorption Characteristic ◽  
Average Absorption Coefficient

Realizing high-efficiency low frequency sound absorption of underwater meta-structures by acoustic siphon effect

2021 ◽  
pp. 2150319
Author(s):  
Li Bo Wang ◽  
Cheng Zhi Ma ◽  
Jiu Hui Wu ◽  
Chong Rui Liu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
High Efficiency ◽  
Physical Mechanism ◽  
Low Frequency ◽  
Area Ratio ◽  
Underwater Acoustic ◽  
Element Simulation ◽  
Average Absorption Coefficient ◽  
New Perspective

The underwater acoustic siphon effect is proposed in this work, which aims to reveal the basic physical mechanism of high-efficiency sound absorption in meta-structures composed of multiple detuned units. Furthermore, the influence of the area ratio on the underwater acoustic siphon effect is then investigated by finite element simulation (FES) and theoretical calculation. On this basis, a meta-structure with the maximum absorption coefficient of almost 100% and average absorption coefficient of 80% at 600–1400 Hz is achieved. The underwater acoustic siphon effect could provide a better understanding of high-efficiency sound absorption and offer a new perspective in controlling underwater noises.

Preliminary Study on Bamboo as Sound Absorber

2014 ◽  
Vol 554 ◽  
pp. 76-80 ◽  
Author(s):  
Fazlin A. Khair ◽  
Azma Putra ◽  
Mohd Jailani Mohd Nor ◽  
Nurul Atiqah ◽  
M.Z. Selamat
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Hollow Structure ◽  
Chemical Substance ◽  
The Body ◽  
Natural Material ◽  
Sound Absorber ◽  
Tube Test ◽  
Average Absorption Coefficient ◽  
Preliminary Study

Synthetic acoustic materials are known for their poisonous chemical substance to the environment and also the particles which are harmful to human health. Research is now directed towards finding an alternative acoustic absorber made from natural materials. This paper presents the utilization of bamboo, a natural material having hollow structure to act as sound absorber. In an impedance tube test, the hollow path is arranged to face the sound incidence. The result reveals that bamboo having length of 2 cm has average absorption coefficient of 0.95 at frequency above 3 kHz. Performance at lower frequencies can be controlled by adding the air gap behind the system. Introduction of microholes along the body shows no significant effect to increase the sound absorption.

Emissivity Calculations for Diatomic Gases

1951 ◽  
Vol 18 (1) ◽  
pp. 53-58
Author(s):  
S. S. Penner
Keyword(s):  
Absorption Coefficient ◽  
Atmospheric Pressure ◽  
Radiant Heat ◽  
Published Data ◽  
Radiant Heat Transfer ◽  
Effective Width ◽  
Combustion Chambers ◽  
Average Absorption Coefficient ◽  
Vibration Rotation ◽  
Simplified Procedure

Abstract An approximate method for estimating radiant-heat transfer from gaseous emitters has been developed. An average absorption coefficient is used for an effective width of an entire vibration-rotation band. The procedure for determining an average absorption coefficient in terms of integrated absorption can be justified, approximately, for very large total pressures where the spectral half-width is no longer small compared with the rotational spacing. Because of this limitation, it is to be expected that the procedure proposed here will be particularly useful only in estimating gaseous emissivities for emitters in high-pressure combustion chambers. Nevertheless, it appears that the simplified procedure yields reasonable results even at relatively low total pressures. Thus a comparison of calculated and observed emissivities for CO at atmospheric pressure shows satisfactory agreement, especially at large optical densities. Representative emissivity calculations over a wide temperature range are described. Emissivity calculations on CO, NO, HF, HCl, HBr, and HI can be carried out very rapidly by the use of recently published data on these gases.

Sound Absorption Characteristics of a Single Micro-Perforated Panel Backed by a Natural Fiber Absorber Material

2020 ◽  
Vol 307 ◽  
pp. 291-296 ◽  
Author(s):  
Meifal Rusli ◽  
Fakhrur Rahman ◽  
Hendery Dahlan ◽  
Gusriwandi ◽  
Mulyadi Bur
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Absorption Characteristic ◽  
Coconut Fiber ◽  
Single Leaf ◽  
Absorber Material ◽  
Resonance Absorber ◽  
Absorption Characteristics

A micro-perforated panel (MPP) works as a Helmholtz-type resonance absorber formed by an air-gab cavity in order to minimize the reflected sound effectively at a selective resonance frequency. Furthermore, the use of natural fibers as sound absorbing materials recently has attracted more attention because it is completely biodegradable, environmental friendly and more economical. In this paper, the combination of MPP and natural fiber as sound absorptive material is investigated. The MPP is made of a transparent acrylic board with 1.5 mm thickness and backed by a coconut fiber panel. The effect of the fiber panel that inserted in the air-gab cavity to the sound absorption characteristic of a single leaf MPP is observed. Sound absorption coefficient is measured by transfer function method using two microphones-impedance tube. It is found that the sandwich model of MPP backed by a coconut fiber changes the sound absorption characteristics of MPP by shifting the maximum absorption coefficient into the lower frequency and making a wider band of frequency absorption. Moreover, the air-gab cavity between MPP and fiber panel give fewer contribution to construct the MPP frequency resonant than the natural fiber panel one.

Utilizing Hollow-Structured Bamboo as Natural Sound Absorber

2015 ◽  
Vol 40 (4) ◽  
pp. 601-608 ◽  
Author(s):  
Azma Putra ◽  
Fazlin Abd Khair ◽  
Mohd Jailani Mohd Nor
Keyword(s):  
Absorption Coefficient ◽  
Hollow Structure ◽  
Front Surface ◽  
Normal Incidence ◽  
Frequency Range ◽  
Peak Absorption ◽  
Natural Sound ◽  
Average Absorption Coefficient ◽  
Lower Frequency Range ◽  
Bamboo Structure

AbstractStudies to find alternative low environmental-impact materials for acoustic absorbers are still progressing, particularly those originated from natural materials. However, most of the established works are mainly focused on the fibrous-type absorbers. Discussion on the non-fibrous-type absorbers is still lacking and this therefore becomes the objective of this paper. Use of bamboo by utilizing its hollow structure to absorb sound energy is discussed here. The normal incidence absorption coefficient was measured based on the length and diameter of the bamboo, as well as different arrangement of the bamboo structure subjected to the incidence sound, namely, axial, transverse, and crossed-transverse arrangements. The trend of absorption coefficient appears in peaks and dips at equally spacing frequencies. For all arrangements the peak of absorption can reach above 0.8. Introducing an air gap behind the bamboo shifts the peak absorption to lower frequency. Covering the front surface of the absorber improves the sound absorption coefficient for axial arrangement by widening the frequency range of absorption also towards lower frequency range. The transverse arrangement is found to have average absorption coefficient peaks of 0.7 above 1.5 kHz. By arranging the bamboo structure with crossed-transverse arrangement, the suppressed absorption peaks in normal transverse arrangement can be recovered.

Sound Absorption Characteristic of Glass and Plastic Bottles: Considerations of Their Dependences on Material Properties

2018 ◽  
Author(s):  
Teruo Iwase ◽  
Satoshi Sugie ◽  
Hiroyasu Kurono ◽  
Masayuki Abe ◽  
Yasuaki Okada ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Resonance Frequency ◽  
Sound Absorption ◽  
Helmholtz Resonator ◽  
Green Building ◽  
Sound Absorption Coefficient ◽  
Absorption Characteristic ◽  
Impedance Change ◽  
Perforated Plates ◽  
Section Area

Great number of bottles made by glass, plastic and metal are used to store beverages, liquid ingredients as water, milk, vinegar and also liqueur. Empty bottles after usage are collected for recycling use and resources. Many of them have narrow open mouth and look like typical shape in kinds of Helmholtz resonator. Authors thought that their reuse for functional building parts with sound absorption would be very valuable from points of view of green building and environmental policies, and authors then measured each resonance frequency and sound absorption coefficient of representative, including light-soft-plastic, bottles, with net capacity from 7 to 2000 ml, by setting on the edge of sound tube with diameter of 100 mm. Sound resonances with sound absorption coefficient of 0.3–1.0 at frequencies from 100 to 1000 Hz clearly depending on the capacity could be confirmed. It was also found that measured result was well matched to the numerical calculation based on acoustic impedance change at each section area gradually changed in bottle. It is thought that combination use of recycled bottles with independent resonance frequency is more effective than use of new uniform perforated plates for wide space where we need additional sound absorption in certain frequency range.

Research on the Absorption Characteristic of Three-Layer Microperforate Plate of the Automotive Body

2011 ◽  
Vol 201-203 ◽  
pp. 2160-2166
Author(s):  
Cong Yun Zhu
Keyword(s):  
Absorption Coefficient ◽  
Equivalent Circuit ◽  
Acoustic Impedance ◽  
Perforated Plate ◽  
Absorption Characteristic ◽  
Perforated Plates ◽  
Automotive Body ◽  
Different Thickness

Three-layer micro perforated plate of the automotive body is researched. Acoustic impedance of the three-layer microperforated plate of the automotive body is attained according to the equivalent circuit, thus absorption coefficient is attained. Different microperforated plate with different porosity, different diameter, different thickness, different depth of cavity of the automotive body is analyzed and some conclusion is drawn to applied some theory to design these types of the micro perforated plates of the automotive body.

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