A modification of a measure of consistency frequently used in the literature is discussed. The modification explicitly takes into account the influence of the connection between the single results and the comparison reference value, where the latter is derived from the values of the current series of measurements. This is of particular importance in situations in which the weighted mean is taken as the reference value.
The necessary target size in acoustic radiation force measurements has not, up to now, been discussed in the literature in a systematic and quantitative manner. Making use of recent progress in the theoretical treatment of the radiation force of three-dimensional sound fields, this paper gives an assessment formula involving the target’s radius and distance from the source which is valid for the field of a baffled, circular, continuously vibrating piston source.
Two different concepts of the Langevin radiation pressure which are ultimately due to Langevin and Brillouin are discussed. The measurement of the radiation force on an absorber at oblique incidence can be regarded as an experimentum crucis in this respect. Herrey’s experimental result, which is confirmed by the author’s observations, is in favor of Brillouin. Some fundamentals and limitations of our present knowledge of the Langevin radiation force in nonabsorbing fluids are considered.
The time-average ultrasonic power emitted by an ultrasonic transducer is one of the key values characterizing the strength of ultrasonic fields as a whole. For medical applications in particular, measurements are usually carried out in water and in the frequency range 1 MHz to 10 MHz. The use of a radiation force balance is recommended in International Electrotechnical Commission Standard IEC 61161. This measurement method and its practical realization at the Physikalisch-Technische Bundesanstalt are described. Uncertainties involved in the primary measurement and in the dissemination process are discussed.
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