Extending the calibration in the Underwater Sound Reference Division (USRD) reciprocity coupler to incorporate phase
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Authors
Slater, William H.
Subjects
acoustic
calibration
coupler
reciprocity
phase
uncertainty
complex uncertainty
H48
hydrophone
Under-water Sound Reference Division
USRD
calibration
coupler
reciprocity
phase
uncertainty
complex uncertainty
H48
hydrophone
Under-water Sound Reference Division
USRD
Advisors
Baker, Steven R.
Crocker, Steven E.
Date of Issue
2016-09
Date
Sep-16
Publisher
Monterey, California: Naval Postgraduate School
Language
Abstract
In this report, a phase measurement is added to the Underwater Sound Reference Division (USRD) reciprocity coupler primary calibration procedure for an H48 reference hydrophone. Data acquisition equipment is added to record time-series data from the hydrophone under test and from the reciprocal transducers. The complex-valued hydrophone sensitivity is calculated. The sensitivity magnitude is compared to measurements from the standard coupler calibration procedure, and the complex sensitivity data are also fitted to a simple high-pass circuit model. The model is used to estimate the low-frequency cutoff of H48 hydrophone SN4. The low-frequency cutoff measured in this report is about 0.2 Hz higher than that originally measured and specified when the H48 hydrophones were first built. The new results show significant roll-off in phase below 10-20 Hz, a range where the phase is typically assumed flat during the standard calibration. By 1 Hz the phase roll-off is about 20°. The error analysis of the original coupler is summarized and error and uncertainty due to new data acquisition equipment and phase measurement added. Some errors due to simplifications in the acoustics of the coupler are left to future work.
Type
Thesis
Description
Series/Report No
Department
Engineering Acoustics Academic Committee
Organization
Identifiers
NPS Report Number
Sponsors
Funder
Format
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.