scholarly journals Ensuring the validity of results of hydrophone calibration by a mutual comparison calibration method

2021 ◽  
Vol 1826 (1) ◽  
pp. 012010
Author(s):  
E G Oliveira ◽  
A V Alvarenga ◽  
R P B Costa-Felix
2021 ◽  
pp. 61-66
Author(s):  
Аlexander М. Еnyakov ◽  
Sergey I. Kuznetsov ◽  
Georgiy S. Lukin

Modern calibration of hydrophones at megahertz frequencies is based on the method of optical interferometry, in which the vibrational velocity of an acoustic wave is measured using a thin sound-transparent polymer foil (membrane), metallized on one side to improve light reflection and installed in an ultrasonic field, followed by its replacement with a hydrophone to be calibrated. The main problem of implementing this calibration method is to assess the adequacy of tracking vibrations of the metallized side of the foil to vibrational displacements of water particles under the action of a sound wave incident on the opposite side of the foil. On the basis of the simplified theory of acoustic plane waves passing through layers of dissimilar materials, methods for measuring the speed of sound in the applied foil and an algorithm for calculating the frequency dependence of the sound wave transmission coefficient (in terms of vibrational velocity) from water through the foil to water or air, introduced as a correction to the results of hydrophone calibration, were developed. The uncertainty of the introduction of this correction is estimated.


Geophysics ◽  
1984 ◽  
Vol 49 (10) ◽  
pp. 1798-1799
Author(s):  
M. H. Safar

One very popular method used for calibrating pressure detectors (hydrophones) in the seismic band is the comparison method. The comparison calibration method, which is widely used (Safar and Newman, 1981) in calibrating marine seismic streamers, can be briefly described as follows. A seismic source is placed at some distance from a standard hydrophone with known transfer function [Formula: see text] and sensitivity factor [Formula: see text]. The pressure detector under test is placed as near as possible to the standard hydrophone so that the Fourier transform of the incident pressure, [Formula: see text], generated by the seismic source at the pressure detector and the standard hydrophone, can be assumed to be the same. Thus the Fourier transform of the output voltages [Formula: see text] and [Formula: see text] of the standard hydrophone and the pressure detector are given as [Formula: see text], (1) and [Formula: see text], (2) where [Formula: see text] and [Formula: see text] are the transfer function and sensitivity factor of the pressure detector. Elimination of [Formula: see text] between equations (1) and (2) gives [Formula: see text]. (3)


1998 ◽  
Vol 3 (2) ◽  
pp. 4-5
Author(s):  
Glenn Pransky

Abstract According to the AMA Guides to the Evaluation of Permanent Impairment, a functional capacity evaluation (FCE) measures an individual's physical abilities via a set of activities in a structured setting and provides objective data about the relationship between an impairment and maximal ability to perform work activities. A key distinction between FCEs and self-reported activities of daily living is that the former involve direct observation by professional evaluators. Numerous devices can quantify the physical function of a specific part of the musculoskeletal system but do not address the performance of whole body tasks in the workplace, and these devices have not been shown to predict accurately the ability to perform all but the simplest job tasks. Information about reliability has been proposed as a way to identify magnification and malingering, but variability due to pain and poor comprehension of instructions may cause variations in assessments. Structured work capacity evaluations involve a set of activities but likely underestimate the individual's ability to do jobs that involve complex or varying activities. Job simulations involve direct observation of an individual performing actual job tasks, require a skilled and experienced evaluator, and raise questions about expense, time, objectivity and validity of results, and interpretation of results in terms of the ability to perform specific jobs. To understand the barriers to return to work, examiners must supplement FCEs with information regarding workplace environment, accommodations, and demotivators.


2009 ◽  
Vol 29 (4) ◽  
pp. 982-986
Author(s):  
Jun ZHANG ◽  
Bang-ping WANG ◽  
Cheng YI ◽  
Xiao-feng LI ◽  
Hui LI

2013 ◽  
Vol 34 (7) ◽  
pp. 1558-1561 ◽  
Author(s):  
Gui-bao Wang ◽  
Hai-hong Tao ◽  
Lan-mei Wang

ROBOT ◽  
2013 ◽  
Vol 35 (5) ◽  
pp. 600 ◽  
Author(s):  
Wenbin GAO ◽  
Hongguang WANG ◽  
Yong JIANG ◽  
Xin'an PAN

ROBOT ◽  
2013 ◽  
Vol 35 (5) ◽  
pp. 521
Author(s):  
Feng WANG ◽  
Kai CHEN ◽  
Xiaoping CHEN

Author(s):  
Vera Rostovtseva ◽  
Vera Rostovtseva ◽  
Igor Goncharenko ◽  
Igor Goncharenko ◽  
Dmitrii Khlebnikov ◽  
...  

Sea radiance coefficient, defined as the ratio of the sunlight reflected by the water bulk to the sunlight illuminating the water surface, is one of the most informative optical characteristics of the seawater that can be obtained by passive remote sensing. We got the sea radiance coefficient spectra by processing the data obtained in measurements from board a moving ship. Using sea radiance coefficient optical spectra it is possible to estimate water constituents concentration and their distribution over the aquatory of interest. However, thus obtained sea radiance coefficient spectra are strongly affected by weather and measurement conditions and needs some calibration. It was shown that practically all the spectra of sea radiance coefficient have some generic peculiarities regardless of the type of sea waters. These peculiarities can be explained by the spectrum of pure sea water absorption. Taking this into account a new calibration method was developed. The measurements were carried out with the portative spectroradiometers from board a ship in the five different seas: at the north-east coast of the Black Sea, in the Gdansk Bay of the Baltic Sea, in the west part of the Aral Sea, in the Kara Sea with the Ob’ Bay and in the Philippine Sea at the coast of Taiwan. The new method of calibration was applied to the obtained spectra of the sea radiance coefficient that enabled us to get the corresponding absorption spectra and estimate the water constituents concentration in every region. The obtained concentration estimates were compared to the values obtained in water samples taken during the same measurement cycle and available data from other investigations. The revealed peculiarities of the sea radiance coefficient spectra in the aquatories under exploration were compared to the corresponding water content and some characteristic features were discussed.


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