Some Measurements of the Absorption Coefficient of Soil, Using the Impedance Tube Technique

Noise Control ◽  
1961 ◽  
Vol 7 (6) ◽  
pp. 20-23
Author(s):  
James H. Prout
Keyword(s):  
Absorption Coefficient ◽  
Impedance Tube

Explainable machine learning: A case study on impedance tube measurements

2021 ◽  
Vol 263 (3) ◽  
pp. 3223-3234
Author(s):  
Merten Stender ◽  
Mathies Wedler ◽  
Norbert Hoffmann ◽  
Christian Adams
Keyword(s):  
Machine Learning ◽  
Absorption Coefficient ◽  
Specimen Thickness ◽  
Learning Models ◽  
Impedance Tube ◽  
Frequency Regime ◽  
Hidden Patterns ◽  
Model Diagnosis ◽  
Machine Learning Models

Machine learning (ML) techniques allow for finding hidden patterns and signatures in data. Currently, these methods are gaining increased interest in engineering in general and in vibroacoustics in particular. Although ML methods are successfully applied, it is hardly understood how these black box-type methods make their decisions. Explainable machine learning aims at overcoming this issue by deepening the understanding of the decision-making process through perturbation-based model diagnosis. This paper introduces machine learning methods and reviews recent techniques for explainability and interpretability. These methods are exemplified on sound absorption coefficient spectra of one sound absorbing foam material measured in an impedance tube. Variances of the absorption coefficient measurements as a function of the specimen thickness and the operator are modeled by univariate and multivariate machine learning models. In order to identify the driving patterns, i.e. how and in which frequency regime the measurements are affected by the setup specifications, Shapley additive explanations are derived for the ML models. It is demonstrated how explaining machine learning models can be used to discover and express complicated relations in experimental data, thereby paving the way to novel knowledge discovery strategies in evidence-based modeling.

Sound Absorption Characteristics of Porous Steel Manufactured by Lost Carbonate Sintering

2009 ◽  
Vol 1188 ◽  
Author(s):  
Miao Lu ◽  
Carl Hopkins ◽  
Yuyuan Zhao ◽  
Gary Seiffert
Keyword(s):  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Single Layer ◽  
Normal Incidence ◽  
Sound Absorption Coefficient ◽  
Absorption Coefficients ◽  
Impedance Tube ◽  
Absorption Characteristics

AbstractThis paper investigates the sound absorption characteristics of porous steel samples manufactured by Lost Carbonate Sintering. Measurements of the normal incidence sound absorption coefficient were made using an impedance tube for single-layer porous steel discs and assemblies comprising four layers of porous steel discs. The sound absorption coefficient was found not to vary significantly with pore size in the range of 250-1500 μm. In general, the absorption coefficient increases with increasing frequency and increasing thickness, and peaks at specific frequencies depending on the porosity. An increase in porosity tends to increase the frequency at which the sound absorption coefficient reaches this peak. An advantage was found in using an assembly of samples with gradient porosities of 75%-70%-65%-60% as it gave higher and more uniform sound absorption coefficients than an assembly with porosities of 75%.

Measurement Method on the Absorption Coefficient of the Material with Large Dimension Based on Two-Microphone

2014 ◽  
Vol 490-491 ◽  
pp. 1584-1587
Author(s):  
Ran Li ◽  
Tao Feng ◽  
Jing Wang ◽  
Yao Wu
Keyword(s):  
Boundary Element Method ◽  
Absorption Coefficient ◽  
Point Source ◽  
Boundary Element ◽  
Measurement Method ◽  
Large Dimension ◽  
Material Surface ◽  
Horizontal Distance ◽  
Impedance Tube ◽  
Indirect Boundary Element Method

This paper is researching on methods to get the absorption coefficient of the material with large dimension. The absorption coefficient can be got by the source mirror method which the FRF of two pressure signals near the material surface in point source field is obtained. The influence of the factors such as the source height, the material size, horizontal distance and positions of two microphones on the accuracy was analyzed by experiments and the indirect boundary element method. The results from this method discussed in this paper are basically the same with that from the impedance tube.

The Process Development for Sound Absorption Design of Non-Woven Car Mat

2020 ◽  
Vol 305 ◽  
pp. 43-48
Author(s):  
Un Hwan Park ◽  
Jun Hyeok Heo ◽  
In Sung Lee ◽  
Dae Kyu Park
Keyword(s):  
Absorption Coefficient ◽  
Physical Properties ◽  
Sound Absorption ◽  
Process Development ◽  
Sound Absorption Coefficient ◽  
Development Effort ◽  
Reverberation Chamber ◽  
Impedance Tube ◽  
Impedance Tubes ◽  
Automotive Interior

Automotive interior material with consists of several material layers has the sound-absorbing function. It is difficult to predict sound absorbing coefficient because of several material layers. So, many experimental tuning is required to achieve the target of sound absorption. Therefore, while the car interior materials are developed, a lot of time and money is spent. In this study, we present the method to predict the sound absorbing performance of the material with multi-layer using physical properties of each material. The properties are predicted by foam-X software using sound absorption coefficient data measured by impedance tube. And we will compare and analyze the predicted sound absorption coefficient with the data measured by scaled reverberation chamber and impedance tubes for a prototype. If the method is used instead of experimental tuning in the development of car interior material, the time and money can be saved. And then, the development effort can be is reduced because it can be optimized by simulation.

scholarly journals Research on the Effect of Imprecise Size Foam Samples on Acoustic Measurements in Impedance Tube

2019 ◽  
Vol 8 (2S11) ◽  
pp. 3045-3049
Keyword(s):  
Absorption Coefficient ◽  
Sample Size ◽  
Transmission Loss ◽  
Small Samples ◽  
Main Role ◽  
Acoustic Measurements ◽  
Polymer Foam ◽  
Control Engineering ◽  
Impedance Tube ◽  
Acoustic Characterization

Polymer foam materials are very commonly used acoustic materials for absorbing sound energy in noise control engineering, because of their higher porosity and light in weight. The acoustic characterization of these materials namely; absorption coefficient and transmission loss are measured using impedance tube, reverberation room method and intensity methods. Among these three impedance tube is the most popular method in laboratory condition. Here the sample size plays a main role in the accurate characterization acoustic materials by using the impedance tube. The present paper discusses effect of variation in the sample size on their acoustic measurements. The foam sample are prepared using Resistance wire foam cutter(RWFC). Their absorption coefficient and transmission loss for large and small samples with variations in sample dimensions are measured and compare with ideal dimension results. A detailed measured data and analysis are done to understand the effect of undersized and oversized foam samples on absorption coefficient and transmission loss results as a function of frequency. The results show that the variations in sample size has immense effect of measured results. The results presented in this study becomes a guideline for characterizing acoustic materials using impedance tube.

TEST METHOD TO DETERMINE THE ACOUSTIC PROPERTIES OF BUILDING MATERIAL BY USING MICROPHONE IMPEDANCE TUBE

Akustika ◽  
2021 ◽  
pp. 36-42
Author(s):  
Sourabh Dogra ◽  
Arpan Gupta
Keyword(s):  
Reflection Coefficient ◽  
Absorption Coefficient ◽  
Virtual Instrument ◽  
Building Materials ◽  
Low Cost ◽  
Test Method ◽  
Wood Fibre ◽  
Acoustic Properties ◽  
Impedance Tube ◽  
Acoustical Properties

The paper discusses a simple and low-cost method to design four microphone impedance tube of measuring the acoustic properties of building materials. The acoustic properties of the material are defined by the reflection coefficient, absorption coefficient, and transmission coefficient. The experimental setup follows the ASTM-E2611 standard of four microphone impedance tube with two load boundary conditions to measure these coefficients. The setup consists of four microphones around a brass tube with the speaker at one end and termination at the other. Raw data from the four microphones is obtained through a Virtual Instrument (VI) program developed in LabView. The novelty in the design is the tapered connection between the two pipes connected via the sample holder. The mathematical equation involved in estimating acoustical properties is solved in MATLAB 2019a. The reflection and absorption coefficient data of ephony fibbrette of 15 mm thickness are compared with the data provided by an accredited laboratory. The experimental results of the in-house designed impedance tube are in good agreement with the lab results. This material is used in the auditorium, theatres for hearing comfort. Further, two new samples of ephony fibbrette along with wood fibre cement and damper has been analysed. It has been found that adding a layer of wood fibre results in an increase in the absorption coefficient whereas the addition of the damper results in an increase in the reflection coefficient.

Measurement Signal Effects on the Normal-Incidence Absorption Coefficient

Volume 1 ◽  
2004 ◽  
Author(s):  
Kuang-Yih Tsuei ◽  
Wen-Wang Jiang ◽  
Shu-Fen Kuo
Keyword(s):  
Plane Wave ◽  
Absorption Coefficient ◽  
Coherence Function ◽  
Normal Incidence ◽  
Measurement Procedure ◽  
Test System ◽  
Test Method ◽  
Impedance Tube ◽  
Measurement Results ◽  
Measurement Signal

This paper will demonstrate the signal effects on the normal-incidence absorption coefficient. The test method covers two microphones located in impedance tube to measure this coefficient. It should analyze the measurement procedure and formulae theoretically, furthermore to propose the coherence function as the criteria for measurement results. Experimentally, different signals, generated by a sound source, input to the loudspeaker in impedance tube to produce the plane wave and two microphones can measure the sound pressures. Through different time weightings and average times on the two microphone signals, and after analyzing results of the frequency response, the coherence function and the normal-incidence absorption coefficient, the coherence function is a major factor to check the normal-incidence absorption coefficient reliable, even the test system stable or not.

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