In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 90, No. 4_Supplement ( 1991-10-01), p. 2263-2263
Abstract:
Ultrasonic fields in the megahertz frequency range are normally characterized using hydrophones, since they are readily available and can measure the spatial and temporal distribution of acoustic pressure. To give absolute results, however, the hydrophone’s response needs to be measured as a function of frequency. Ideally, the amplitude and phase response should be known in the frequency range 0.3–100 MHz. At the National Physical Laboratory (NPL), four methods have been used for calibration−planar scanning, two-transducer reciprocity, laser interferometry, and the so-called magnomic method. Planar scanning and reciprocity agree with the results of other techniques in the range 0.5–15 MHz, but they are increasingly difficult to apply at frequencies above 10 MHz. Laser interferometry is the primary method used at NPL and gives overall uncertainties at the 95% confidence level of between 2.5% and 5% over the frequency range 0.3–20 MHz. The magnomic method has recently been used to measure the amplitude and phase response from 5 to 100 MHz. The results are in agreement with the interferometric method at low frequencies and with predictions of the frequency response of the hydrophone at higher frequencies. NPL has recently been the pilot laboratory for a European intercomparison of calibrations (funded by the Community Bureau of Reference) in which four other laboratories participated. The results of this comparison will be described briefly.
Type of Medium:
Online Resource
ISSN:
0001-4966
,
1520-8524
Language:
English
Publisher:
Acoustical Society of America (ASA)
Publication Date:
1991
detail.hit.zdb_id:
1461063-2
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