scholarly journals Room‐average absorption coefficient determination by means of intesity measurements in steady‐state acoustic field conditions

1990 ◽  
Vol 87 (S1) ◽  
pp. S10-S10
Author(s):  
Domenico Stanzial ◽  
Augusto Fuschini
Keyword(s):  
Steady State ◽  
Absorption Coefficient ◽  
Acoustic Field ◽  
Field Conditions ◽  
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.

Light-induced absorption and optical damage in Sc-, Mg-, and Zn-doped near-stoichiometric LiNbO3

2018 ◽  
Vol 27 (03) ◽  
pp. 1850030 ◽  
Author(s):  
Junsheng Li ◽  
Youwen Liu ◽  
Huijie Zhang ◽  
Liangzun Tang ◽  
Chongjun He
Keyword(s):  
Steady State ◽  
Lithium Niobate ◽  
Absorption Coefficient ◽  
Ultraviolet Light ◽  
Infrared Absorption ◽  
Doping Level ◽  
Doping Concentration ◽  
Weak Absorption ◽  
Induced Absorption ◽  
Infrared Absorption Spectra

By measuring the ultraviolet-light-induced absorption in Sc-, Mg- and Zn-doped near-stoichiometric lithium niobate (LiNbO[Formula: see text], we find that the steady-state ultraviolet-light-induced absorption coefficient changes with respect to the doping concentration. There is a strong ultraviolet-light-induced absorption when doping concentration is below its photorefractive threshold and a really weak absorption when the crystal is highly doped. We also use OH[Formula: see text] infrared absorption spectra and the transmitted light spot distortion method to verify the result. Thus, we can determine if the doping level in these doped near-stoichiometric LiNbO3 crystals is above or below their photorefractive threshold by measuring the ultraviolet-light-induced absorption.

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.

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.

scholarly journals The influence of the distribution of sound absorbing materials on the estimation of reverberation time in rooms

2018 ◽  
Vol 49 ◽  
pp. 00078
Author(s):  
Marcelina Olechowska ◽  
Artur Nowoświat ◽  
Jan Ślusarek ◽  
Mateusz Latawiec
Keyword(s):  
Absorption Coefficient ◽  
Acoustic Field ◽  
Sound Absorption ◽  
Sound Field ◽  
Reverberation Time ◽  
Type D ◽  
Absorbing Materials ◽  
Absorbing Material ◽  
Different Dimensions ◽  
Materials Used

Reverberation time in rooms depends on many factors, e.g. cubature, surface of envelopes, sound absorption coefficient of materials used for the construction of the envelopes, geometry of rooms or the distribution of sound absorbing materials. The arrangement of sound absorbing materials in rooms has an impact on the dispersion of acoustic field, yet theoretical calculation models do not take into account this impact. According to these models, regardless of the arrangement of sound absorbing materials, the reverberation time in a room will remain unchanged. The present paper investigates the above problem by means of computer simulations. For the needs of the simulation, three rooms with different dimensions were adopted, i.e. type 'p' - a cuboidal room with a square base, type 'd' - a cuboidal room (with one side of the 'p' room lengthened), type 'w' - a cuboidal room (with the height of the room lengthened 'p'). During the simulation, the way of acoustic field dispersion was being changed and its influence on the reverberation time in the rooms was being determined. The authors investigated two situations. The first one involved a non-dampened room, in which the sound absorbing material was being arranged differently. The second one involved a welldampened room, and the dispersion of sound field was analyzed depending on the location of the reflecting material.

scholarly journals Measurement of the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field

2014 ◽  
Vol 136 (1) ◽  
pp. EL13-EL19 ◽  
Author(s):  
Olivier Robin ◽  
Alain Berry ◽  
Olivier Doutres ◽  
Noureddine Atalla
Keyword(s):  
Absorption Coefficient ◽  
Acoustic Field ◽  
Absorbing Materials

A Numerical Study of a Method for Estimating Sound Absorption Coefficient under a Synthesized Diffuse Acoustic Field

2016 ◽  
Vol 9 (3) ◽  
pp. 1111-1116
Author(s):  
Olivier Robin ◽  
Celse Kafui Amedin ◽  
Alain Berry ◽  
Noureddine Atalla ◽  
Olivier Doutres ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Acoustic Field ◽  
Sound Absorption ◽  
Numerical Study ◽  
Sound Absorption Coefficient
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