Elektroakustika a ultrazvuk

Oblast zaměření: Elektroakustika a ultrazvuk
Komise : IEC/TC 87 (Ultrasonics)
K připomínkám do: 3.04.2019
Zobraz více Zobraz méně

This International Standard specifies methods and procedures for free-field calibration of hydrophones, as well as individual electroacoustic transducers that can be used as hydrophones (receivers) and/or projectors (source transducers). Two general types of calibration are covered within this standard: absolute calibration using the method of three-transducer spherical-wave reciprocity, and relative calibration by comparison with a reference device which has already been the subject of an absolute calibration.

The maximum frequency range of the methods described in this standard is from 200 Hz to 1 MHz. The lowest acoustic frequency of application will depend on a number of factors, and will typically be in the range 200 Hz to 5 kHz depending mainly on the dimensions of the chosen test facility, The highest frequency of application for the methods described here is 1 MHz.

Procedures for pressure hydrophone calibration at low frequencies can be found in IEC 60565-2 [1]. Procedures for hydrophone calibration at acoustic frequencies greater than 1 MHz are covered by IEC 62127-2 [2].

Excluded from the scope of this standard are low frequency pressure calibrations of hydrophones, which are described in IEC 60565-2 [1]. Also excluded are calibrations of digital hydrophones and systems, calibration of marine autonomous acoustic recorders, calibration of vector sensors such as particle velocity sensors and pressure gradient hydrophones, calibration of passive sonar arrays consisting of multiple hydrophones, and calibration of active sonar arrays consisting of projectors and hydrophones.

This standard presents a description of the requirements for free-field calibration in terms of test facility, equipment and instrumentation, signal processing, and frequency limitations. A description of achievable uncertainty and rules for the presentation of the calibration data are provided. Also included are informative annexes that provide additional guidance. Annex A provides guidance on measurement of directional response of a hydrophone or projector. Annex B provides guidance on measurement of electrical impedance of hydrophones and projectors. Annex C provides guidance on electrical loading corrections. Annex D provides guidance on acoustic far-field criteria in underwater acoustic calibration. Annex E provides guidance on pulsed techniques in free-field calibrations. Annex F provides guidance on assessment of uncertainty in the free-field calibration of hydrophones and projectors. Annex G describes the derivation of the formulae for three-transducer spherical-wave reciprocity calibrations. Annex H provides guidance on calibration using travelling wave-tubes. Annex I provides guidance on calibration of hydrophones using optical interferometry. And finally, Annex J provides guidance on calibrations in reverberant water tanks using continuous signals.