Measurement of sound absorption coefficient in a reverberant room using probability density function of damping constant

2021 ◽  
Vol 263 (4) ◽  
pp. 2940-2948
Author(s):  
Kosuke Goto ◽  
Takehiko Nakagawa ◽  
Yoshinari Yamada
Keyword(s):  
Probability Density Function ◽  
Absorption Coefficient ◽  
Spatial Variability ◽  
Measurement Method ◽  
Sound Absorption ◽  
Measurement Accuracy ◽  
Sound Absorption Coefficient ◽  
Reverberation Time ◽  
Low Frequencies ◽  
Sinusoidal Input

The measurement method of the sound absorption coefficient in a reverberation room is standardized in ISO 354. However, the measurement accuracy often deteriorates at low frequencies. This paper proposes a method that improves the measurement accuracy of the sound absorption coefficient at low frequencies. It calculates the sound absorption coefficient using reverberation time (RT) that is derived from the distribution of a damping constant for a sinusoidal input. The measured values by the proposed method were compared with those by the ISO 354 method. As a result, the proposed method reduces the spatial variability of RT and gives a better agreement with the statistical absorption coefficient that is calculated by a transfer matrix model at low frequencies.

scholarly journals Sound Absorption Performance of Sugar Palm Trunk Fibers

2019 ◽  
Vol 130 ◽  
pp. 01003
Author(s):  
Anditya Endar Prabowo ◽  
Kuncoro Diharjo ◽  
Ubaidillah ◽  
Iwan Prasetiyo
Keyword(s):  
Absorption Coefficient ◽  
Bulk Density ◽  
Sound Absorption ◽  
Random Noise ◽  
Air Gap ◽  
Sound Absorption Coefficient ◽  
Low Frequencies ◽  
Central Java ◽  
Absorption Performance ◽  
Small Medium Enterprises

The purpose of this research is to investigate the effect of bulk density, thickness, and air gap to sound absorption performance on absorber based sugar palm trunk fibers. The fibers were obtained from solid waste on Small-Medium Enterprises of sago flour processing in Klaten, Central Java, Indonesia. The absorber specimens were formed from the fibers using a simple press molding in an oven at 150 °C. According to ISO 10534-2, the absorber samples were tested using two microphones impedance tube with random noise source to get the curve of the sound absorption coefficient. The result shows that the absorption performance can be improved by increasing bulk density and increasing of sample thickness. Especially at low frequencies, improvement of the sound absorption coefficient can be achieved (NAC > 0.8) by applying the air gap behind the sample. The best performance of absorber based sugar palm trunk fiber can be achieved for (1 000 to 6 000) Hz range frequency.

scholarly journals Experimental Sound Absorption of Several Loose Uncooked Granular Materials

2019 ◽  
Vol 9 (1) ◽  
pp. 4578-4583
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Grain Shape ◽  
Experimental Tests ◽  
Sound Absorption Coefficient ◽  
Acoustic Absorption ◽  
Low Frequencies ◽  
Acoustic Insulation ◽  
Acoustic Absorption Coefficient ◽  
First Time

Absorbent materials it's an acoustic solution that can be used to control the reverberation time (RT) in deferent spaces as: conference rooms, in halls, theaters, cinema.... and also, it can be used in walls or ceilings of buildings to improve the acoustic insulation Which can be used for internal separations between spaces. This study focuses on the experimental study of the acoustic absorption coefficient of several granular food materials as a function of frequency 50 to 1600 Hz. All acoustic absorption tests performed in this study are performed by an acoustic impedance tube or Kundt tube. And to the knowledge of the author it is the first time in the literature that someone studies the acoustic behavior of this kind of materials. Several parameters were studied such as the effect of thickness on the sound absorption coefficient of the materials tested, like the influence of the grain form on the acoustic absorption by the introduction of a new parameter L / D, and finally the influence of density and type of material on the sound absorption coefficient. The objective of this work is to study the influence of the grain shape on the sound absorption coefficient, and that's why we have chosen these fifteen materials each one with its own shape. The results of these experimental tests show that when the sample thickness rises, the acoustic absorption coefficient rises too with a shift from resonance frequency to low frequencies. When the L/D parameter rises, the absorption behavior increases too in all frequencies mentioned. Finally, as the density of the tested material rises, the percentage of sound absorption of the materials also rises

Analysis of Sound Absorption of Date Palm Fibers Based on Flow Resistivity

2013 ◽  
Vol 471 ◽  
pp. 285-290 ◽  
Author(s):  
Elwaleed Awad Khidir ◽  
Mojahed Osman Mohammed Ali ◽  
Mohammed Mustafa Ali ◽  
Mohd Faizal Bin Mat Tahir ◽  
Rozli Zulkifli
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Date Palm ◽  
Single Layer ◽  
Sound Absorption Coefficient ◽  
Low Frequencies ◽  
Palm Fiber ◽  
Date Palm Fibers ◽  
Flow Resistivity ◽  
Fiber Sample

This paper presents a study on the sound absorption properties of a single layer date palm fiber based on the flow resistivity. Experimental measurements were carried out to estimate the flow resistivity value using differential pressure tube. The average diameter of the fibers is 0.462 mm. A date palm fiber sample of 25mm thickness is used in this research. The flow resistivity of the date palm fiber sample was found to be 4.26 kPa.s/m2. The flow resistivity was used to calculate the sound absorption coefficient using Delany and Bazley model. The simulation showed that the values of absorption coefficient are small at low frequencies and rising with increasing frequency. To check the effect of flow resistivity on the sound absorption coefficient Delany and Bazley model was simulated for three different flow resistivity values. The simulation results showed that the sound absorption coefficient increases with the increase of the flow resistivity.

scholarly journals Sound absorption characteristics of three species (binuang, balsa and paulownia) of low density hardwood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Eun-Suk Jang ◽  
Chun-Won Kang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Sound Absorption Coefficient ◽  
Low Density ◽  
High Porosity ◽  
Sound Waves ◽  
Low Frequencies ◽  
Absorption Performance ◽  
Closed Pore

Abstract In this study, the sound absorption coefficient of three low density hardwoods – binuang, balsa and paulownia – were investigated. Their gas permeability and pore size were measured, and their pore shapes were classified into through pore, blind pored, and closed pore, as specified by the International Union of Pure and Applied Chemistry (IUPAC). Among the three species, obvious that paulownia had lowest sound absorption when the two of others showed higher sound absorption. Although paulownia is a high porosity wood, most of its vessels are blocked by tyloses; it is therefore difficult for sound waves to enter its pores, which results in poor sound absorption performance. This study showed that the higher the through pore porosity, the higher was the gas permeability, which led to improvement of the sound absorption performance. It was also found that the sound absorption coefficient of the three species woods increased at low frequencies as the size of an air cavity between the specimens and tube’s wall increased.

Sound absorption coefficient assessment of sisal, coconut husk and sugar cane fibers for low frequencies based on three different methods

2019 ◽  
Vol 156 ◽  
pp. 92-100 ◽  
Author(s):  
Claudia Cilene Bittencourt da Silva ◽  
Fernando Jun Hattori Terashima ◽  
Nilson Barbieri ◽  
Key Fonseca de Lima
Keyword(s):  
Absorption Coefficient ◽  
Sugar Cane ◽  
Sound Absorption ◽  
Sound Absorption Coefficient ◽  
Low Frequencies ◽  
Coconut Husk

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

scholarly journals Air permeability and sound absorption coefficient changes from ultrasonic treatment in a cross section of Malas (Homalium foetidum)

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Chun-Won Kang ◽  
Eun-Suk Jang ◽  
Nam-Ho Lee ◽  
Sang-Sik Jang ◽  
Min Lee
Keyword(s):  
Absorption Coefficient ◽  
Ultrasonic Treatment ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Treated Wood ◽  
Untreated Wood ◽  
Sound Absorption Coefficient ◽  
Permeability Constant ◽  
Average Value ◽  
Permeability Increase

AbstractWe investigated the effect of ultrasonic treatment on Malas (Homalium foetidum) gas permeability and sound absorption coefficient using the transfer function method. Results showed a longitudinal average Darcy permeability constant of 2.02 (standard deviation SD 0.72) for untreated wood and 6.15 (SD 3.07) for ultrasound-treated wood, a permeability increase of 3.04 times. We also determined the average sound absorption coefficients in the range of 50 to 6.4 kHz and NRC (noise reduction coefficient: average value of sound absorption coefficient value at 250, 500, 1000, and 2000 Hz) of untreated Malas. Those values were 0.23 (SD 0.02) and 0.13 (SD 0.01), respectively, while those of ultrasonic-treated Malas were 0.28 (SD 0.02) and 0.14 (SD 0.02), a 19.74% increase in average sound absorption coefficient.

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