The measurement of sound absorption coefficients

Sabine, Paul E.

doi:10.1016/s0016-0032(29)91450-2

Cited by 18 publications

(6 citation statements)

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“…where a is the constant 13.8155 and t is the time (in seconds) between the initial and final sound intensity measurements. An empirical relation between reverberation time and the absorption coefficients was first found by W.C Sabine [12] before 1920 which is still used for estimating reverberation time from absorption coefficients.…”

Section: Non-parallel Walls and Skewed Surfacesmentioning

confidence: 99%

An Overview of Acoustic Impedance Measurement Techniques and Future Prospects

et al. 2021

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In order to progress in the area of aeroacoustics, experimental measurements are necessary. Not only are they required for engineering applications in acoustics and noise engineering, but also they are necessary for developing models of acoustic phenomenon around us. One measurement of particular importance is acoustic impedance. Acoustic Impedance is the measure of opposition of acoustical flow due to the acoustic pressure. It indicates how much sound pressure is generated by the vibration of molecules of a particular acoustic medium at a given frequency and can be a characteristic of the medium.The aim of the present paper is to give a synthetic overview of the literature on impedance measurements and to discuss the advantage and disadvantage of each measurement technique. In this work, we investigate the three main categories of impedance measurement techniques, namely reverberation chamber techniques, impedance tube techniques, and far-field techniques. Theoretical principles for each technique are provided along with a discussion on historical development and recent advancements for each technique.

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Section: Non-parallel Walls and Skewed Surfacesmentioning

confidence: 99%

An Overview of Acoustic Impedance Measurement Techniques and Future Prospects

et al. 2021

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“…9. The composite samples reinforced with bio-materials having varied weight percentages of blend of bio-benzoxazine/epoxy matrices were developed and their sound absorption co-e ciency (SAC) (Sabine 1929) was assessed in order to utilize them for acoustic proof panels. The values of SAC obtained for natural bers reinforced biobenzoxazine/epoxy composites are increased up to 50-1600 Hz with 100mm and 500-6400 Hz with 29mm specimens of circular types.…”

Section: Acoustic Propertiesmentioning

confidence: 99%

Rice husk and saw dust reinforced hybridized blends of bio-benzoxazine/epoxy based composites: Thermal, Mechanical, and Acoustic Absorption Properties

Arumugam

Krishnasamy

Dilip

et al. 2021

Preprint

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The prime objective of the present work is to develop bio-wastes (rice husk and saw dust) reinforced composites with varying weight percentages composition of hybridized blend made from bio-based cardanol-melamine, cardanol-aniline benzoxazine and epoxy resin (bio-benzoxazine : epoxy resin 0:100 and 50:50 wt%)for acoustic proof applications. The breakthrough achieved in the present work is the cardanol benzoxazine is made in the form of hybrid matrix with epoxy resin, which cures significantly at lower temperature of 1050C in the absence of any curatives and also cures at room temperature in the presence of isophorone diamine curative,whereas the cardanol-melamine and cardanol-aniline based benzoxazines cure at very high temperature of 221˚C and 275 ˚C respectively. The low temperature cure behaviour achieved in the present work facilitates the amenable fabrication of bio-composites using both low heat resistant bio-based reinforcements and high temperature cure bio-benzoxazines for making cost competitive green building materials. Cardanol-melamine (C-m) and cardanol-aniline (C-a) based benzoxazines were synthesised using cardanol separately with melamine (m) and aniline (a) in the presence of paraformaldehyde under suitable experimental conditions. The benzoxazine (C-m and C-a) obtained was blended with varying weight percentages of bisphenol-A epoxy (DGEBA) resin separately followed by reinforcing with rice husk and saw dust and then cured at room temperature with stoichiometric quantity of isophorone diamine to obtain corresponding hybrid bio-composites. Mechanical properties (tensile strength, modulus, percentage elongation and hardness), thermal conductivity, thermal resistance, and sound absorption coefficient were studied as per standard methods. Results obtained from different studies infer that hybrid blended cardanol benzoxazine composite panels reinforced with rice husk and saw dust possess appreciable thermal, mechanical and acoustic properties. Data obtained from acoustic studies, it was observed that the highest value of sound absorption coefficient of 6400 Hz was noticed for composite specimens developed using both rice husk and saw dust reinforced with hybridized blend of bio-benzoxazine (50wt%) and epoxy resin (50wt%) and these hybrid composite panels can be used as sound absorption material in the ceiling and wall construction applications.

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“…In 1931, Knudsen 2 proved that this effect was not caused by a change of acoustical absorption properties of the surface material, but by the change of acoustical absorption properties of the air, when temperature and humidity change. A substantial amount of research has been devoted to producing a calculation model for pure tone air absorption based on sound decay measurements in reverberation rooms [1][2][3][4] and impedance tubes or spheres, [5][6][7][8][9][10] with varying frequency ranges, gas mixtures, and ambient conditions. The final calculation model is explained in literature [11][12][13] and has been incorporated in currently used national and international standards for the calculation of the absorption of sound by the atmosphere ANSI S1.…”

Section: Introduction a Air Absorptionmentioning

confidence: 99%

“…(1). Because this paper deals with room acoustics, the phenomenon will be referred to as "air absorption" and the intensity attenuation coefficient m is used.…”

Section: Introduction a Air Absorptionmentioning

confidence: 99%

The effective air absorption coefficient for predicting reverberation time in full octave bands

Wenmaekers

Hak

Hornikx

2014

The Journal of the Acoustical Society of America

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A substantial amount of research has been devoted to producing a calculation model for air absorption for pure tones. However, most statistical and geometrical room acoustic prediction models calculate the reverberation time in full octave bands in accordance with ISO 3382-1 (International Organization for Standardization, 2009). So far, the available methods that allow calculation of air absorption in octave bands have not been investigated for room acoustic applications. In this paper, the effect of air absorption on octave band reverberation time calculations is investigated based on calculations. It is found that the approximation method, as described in the standard ANSI S1.26 (American National Standards Institute, 1995), fails to estimate accurate decay curves for full octave bands. In this paper, a method is used to calculate the energy decay curve in rooms based on a summation of pure tones within the band. From this decay curve, which is found to be slightly concave upwards, T 20 and T 30 can be determined. For different conditions, an effective intensity attenuation coefficient m B;eff for the full octave bands has been calculated. This m B;eff can be used for reverberation time calculations, if results are to be compared with T 20 or T 30 measurements. Also, guidelines are given for the air absorption correction of decay curves, measured in a scale model.

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The measurement of sound absorption coefficients

Cited by 18 publications

References 0 publications

An Overview of Acoustic Impedance Measurement Techniques and Future Prospects

An Overview of Acoustic Impedance Measurement Techniques and Future Prospects

Rice husk and saw dust reinforced hybridized blends of bio-benzoxazine/epoxy based composites: Thermal, Mechanical, and Acoustic Absorption Properties

The effective air absorption coefficient for predicting reverberation time in full octave bands

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