2023_programme: Multivariate control charts for calibration of hydrophones using the Mahalanobis distance

• Session: 18. Underwater acoustic calibration and standards
  Organiser(s): Stephen Robinson, Markus Linné and Victor Évora
• Lecture: Multivariate control charts for calibration of hydrophones using the Mahalanobis distance
  Paper ID: 1978
  Author(s): Crocker Steven, Slater William
  Presenter: Slater William
  Abstract: Statistical analysis of data to ensure the validity of calibrations can be challenged when the measurement model describes a process and result that spans a high-dimensional parameter space. Calibration of hydrophones presents one such case whereby the sensitivity to acoustic pressure is calculated using measured values for several different quantities and the result is needed at many excitation frequencies distributed over a large bandwidth. To address this challenge, a multivariate statistical analysis procedure was developed that supports efficient and effective process control for hydrophone calibrations. It first characterizes the in-control condition by the mean and covariance of measurements expressed in a p-dimensional parameter space using a curated training data set. The procedure then tests subsequent measurements against a control limit using Hotelling’s T2-test to compare the current measurement process to the training data. A case study for free-field calibration of hydrophones spanning a frequency range of 1 kHz to 200 kHz is described. An emergent defect in a measuring instrument was detected by inspection of data presented in a multivariate control chart, thus helping to ensure the validity of calibration results reported in certificates issued by the laboratory.
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• Corresponding author: Mr William Slater
  Affiliation: Naval Undersea Warfare Center
  Country: United States
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