| 1. |
- Brezas, Spyros, et al.
(author)
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Dissemination of the unit watt in airborne sound : Aerodynamic reference sound sources as transfer standards
- 2016
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In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering. - 9783939296119 ; , s. 6762-6770
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Conference paper (peer-reviewed)abstract
- In the process aiming at the establishment of both traceability and transparent uncertainty budgets for airborne sound power, the dissemination of the unit watt ensures the correct relation between the sound power of a stationary primary standard and the sound power of transportable transfer standards. The paper reports on a detailed study to qualify aerodynamic reference sound sources (RSSs) as transfer standards. The temporal stability of RSSs has been determined for both narrow and broad frequency bands. Specially designed scanning apparatuses have provided directivity results. Remaining room reflections and near field effects have also been studied. The dissemination also requires the prediction of sound power under meteorological (static pressure, ambient temperature) and operating (rotational speed) conditions different from calibration conditions. These influences have been investigated and a correction is proposed. Finally, interlaboratory measurement results of the sound power of an aerodynamic reference sound source are reported.
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| 2. |
- Guglielmone, Claudio, et al.
(author)
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Main achievements of the EMRP sound power project and future prospects
- 2016
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In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering. - 9783939296119 ; , s. 6811-6817
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Conference paper (peer-reviewed)abstract
- An independent method for the measurement of sound power, based on a primary standard traceable to units tied to fundamental constants, has been realised and tested. The most important achievement is that the uncertainty evaluation can be deduced in a direct and (mostly) analytical way from the primary standard and measurement environment parameters, both hemi free and reverberant acoustical fields have been considered. A new traceability line to the primary standard has been established, and the validity of the already available transfer standards has been investigated. All these achievements have the revision of the sound power measurement procedures, for which developments and validation has been carried out during the project, as a goal. Dissemination has been realised by papers, participation in conferences and a seminar. Future work will focus on improvement of the frequency range and uncertainty of the primary standard, establishment of measurement capabilities by means of key comparisons in the EURAMET region, declarations of services in the CIPM database and proposed revision of the ISO standards concerning sound power. Another important task is working among the acoustic industrial and metrological community to foster the acceptance of the new methods. Applications to calibration of microphone arrays are also possible.
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| 3. |
- Kirbaş, Cafer, et al.
(author)
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Primary sound power sources for the realisation of the unit watt in airborne sound
- 2016
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In: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering. - 9783939296119 ; , s. 6737-6748
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Conference paper (peer-reviewed)abstract
- At present, airborne sound power is not a directly measurable quantity. It is calculated from sound pressure measurements performed in special environments, e.g. free or diffuse fields or from sound intensity measurements using 2-microphone probes. All the different methods are lacking traceability and transparent uncertainty budgets. These deficiencies are finally based on the lack of a primary standard for sound power as the metrological basis. In the joint research project funded by the European Metrology Research Program, primary sound power standards were established on the base of the Rayleigh Integral Method where the sound power is calculated from measured velocities on a baffled vibrating body. Different reference sound power sources were designed in different Institutes. The construction of the primary sources was mainly focused on the piston; its material, shape and friction during its movement. Primary sound power sources were installed in hemi anechoic and reverberant environments, and characterisation measurements were performed to see the effect of different environments on the sound power output. Comparison measurements were performed to compare the new and present methods for the primary sound power source.
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