Determination of Measurement Uncertainties in Building Acoustics by Interlaboratory Tests. Part 2: Sound Absorption Measured in Reverberation Rooms

2018 ◽  
Vol 104 (6) ◽  
pp. 999-1008 ◽  
Author(s):  
Volker Wittstock
Keyword(s):  
Sound Absorption ◽  
Measurement Uncertainties ◽  
Building Acoustics

scholarly journals Development and Validation of Optical Methods for Zeta Potential Determination of Silica and Polystyrene Particles in Aqueous Suspensions

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 290
Author(s):  
Yannic Ramaye ◽  
Marta Dabrio ◽  
Gert Roebben ◽  
Vikram Kestens
Keyword(s):  
Zeta Potential ◽  
Particle Tracking ◽  
Colloidal Stability ◽  
Optical Methods ◽  
Intermediate Precision ◽  
Electrophoretic Light Scattering ◽  
Measurement Uncertainties ◽  
Development And Validation ◽  
Direct Implementation

Zeta potential is frequently used to examine the colloidal stability of particles and macromolecules in liquids. Recently, it has been suggested that zeta potential can also play an important role for grouping and read-across of nanoforms in a regulatory context. Although the measurement of zeta potential is well established, only little information is reported on key metrological principles such as validation and measurement uncertainties. This contribution presents the results of an in-house validation of the commonly used electrophoretic light scattering (ELS) and the relatively new particle tracking analysis (PTA) methods. The performance characteristics were assessed by analyzing silica and polystyrene reference materials. The ELS and PTA methods are robust and have particle mass working ranges of 0.003 mg/kg to 30 g/kg and 0.03 mg/kg to 1.5 mg/kg, respectively. Despite different measurement principles, both methods exhibit similar uncertainties for repeatability (2%), intermediate precision (3%) and trueness (4%). These results confirm that the developed methods can accurately measure the zeta potential of silica and polystyrene particles and can be transferred to other laboratories that analyze similar types of samples. If direct implementation is impossible, the elaborated methodologies may serve as a guide to help laboratories validating their own methods.

Method of Testing of Sound Absorption Properties of Materials Intended for Ultrasonic Noise Protection

2013 ◽  
Vol 38 (2) ◽  
pp. 191-195 ◽  
Author(s):  
Dariusz Pleban
Keyword(s):  
Sound Absorption ◽  
Free Field ◽  
Tone Burst ◽  
Mineral Wool ◽  
Frequency Range ◽  
Absorption Properties ◽  
Open Cell Foam ◽  
Properties Of Materials ◽  
Cell Foam

Abstract Efficient ultrasonic noise reduction by using enclosures requires the knowledge of absorbing properties of materials in the frequency range above 4 kHz. However, standardized methods enable determination of absorption coefficients of materials in the frequency range up to 4 kHz. For this reason, it is proposed to carry out measurements of the sound absorption properties of materials in the free field by means of a tone-burst technique in the frequency range from 4 kHz to 40 kHz at angles of incidence varying from 0° to 60°. The absorption coefficient of a material is calculated from the reflection coefficient obtained by reflecting a tone-burst from both a perfectly reflecting panel and a combination of this panel and the sample of the tested material. The tests results show that mineral wool and polyurethane open-cell foam possess very good absorbing properties in this frequency range.

scholarly journals Measurement Uncertainties Encountered During Gas Turbine Driven Compressor Field Testing

1998 ◽  
Author(s):  
Klaus Brun ◽  
Rainer Kurz
Keyword(s):  
Measurement Uncertainty ◽  
Gas Turbine ◽  
Field Test ◽  
Equations Of State ◽  
Accurate Determination ◽  
Field Testing ◽  
Significant Implication ◽  
Test Results ◽  
Measurement Uncertainties

Field testing of gas turbine compressor packages requires the accurate determination of efficiency, capacity, head, power and fuel flow in sometimes less than ideal working environments. Nonetheless, field test results have significant implication for the compressor and gas turbine manufacturers and their customers. Economic considerations demand that the performance and efficiency of an installation are verified to assure a project’s return on investment. Thus, for the compressor and gas turbine manufacturers, as well as for the end-user, an accurate determination of the field performance is of vital interest. This paper describes an analytic method to predict the measurement uncertainty and, thus, the accuracy, of field test results for gas turbine driven compressors. Namely, a method is presented which can be employed to verify the validity of field test performance results. The equations governing the compressor and gas turbine performance uncertainties are rigorously derived and results are numerically compared to actual field test data. Typical field test measurement uncertainties are presented for different sets of instrumentation. Test parameters that correlate to the most significant influence on the performance uncertainties are identified and suggestions are provided on how to minimize their measurement errors. The effect of different equations of state on the calculated performance is also discussed. Results show that compressor efficiency uncertainties can be unacceptably high when some basic rules for accurate testing are violated. However, by following some simple measurement rules and maintaining commonality of the gas equations of state, the overall compressor package performance measurement uncertainty can be limited and meaningful results can be achieved.

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