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SOEMS

Source: vignettes/calibration/index.Rmd
index.Rmd

Overview

Benchmarked Validated
Theory Implementation

The solid elastic sphere modal-series model (SOEMS) calculates the reference response of homogeneous metal calibration spheres. In package calls, select it with model = "calibration" or the soems alias.

Core idea

Expand the exterior acoustic field and the solid’s longitudinal and shear displacements in spherical modes, enforce the fluid-solid interface conditions, and sum the elastic phase shifts (Hickling 1962; MacLennan 1981).

Best for

  • Standard-target calibration spheres made from homogeneous elastic solids
  • Frequency-dependent reference spectra for specified sphere materials and diameters
  • Comparison with published calibration-sphere calculations

Supports

  • CAL objects created with cal_generate()
  • Built-in calibration materials or user-supplied density and longitudinal and shear speeds
  • Adaptive or fixed modal truncation

Main assumptions

  • A perfectly spherical, homogeneous isotropic solid
  • Linear elasticity within the sphere and an inviscid exterior fluid
  • No coating, shell, cavity, or material gradient
  • Material and water properties match the actual calibration conditions

Validation status

  • Benchmarked against published calibration-sphere targets used throughout the package documentation.
  • Validated against echoSMs, SphereTS, and the NOAA calibration applet.

Family pages

  • Implementation: building standards, spectra, and external comparisons
  • Theory: elastic potentials, interface conditions, and phase shifts

Calibration workflow

Calibration workflow map Four-stage calibration workflow from nominal sphere specification through property verification, model execution, and reference-curve interpretation. Calibration as a reference workflow rather than a generic scattering run1. Define the sphereDiameter, material properties,elastic properties2. Verify propertiesDensity, sound speeds, elasticconstants3. Run the modelUse the instrument frequencygrid and inspect sensitivity4. Interpret as referenceCompare against standards andtreat mismatches as diagnostic

A calibration calculation is only a reference when diameter, material properties, surrounding water, and frequency match the physical standard (Dragonette et al. 1981; Foote 1990). The material-properties guide covers non-default inputs.

References

Dragonette, Louis R., S. K. Numrich, and Laurence J. Frank. 1981. “Calibration Technique for Acoustic Scattering Measurements.” The Journal of the Acoustical Society of America 69 (4): 1186–89. https://doi.org/10.1121/1.385699.
Foote, K. G. 1990. “Spheres for Calibrating an Eleven-Frequency Acoustic Measurement System.” ICES Journal of Marine Science 46 (3): 284–86. https://doi.org/10.1093/icesjms/46.3.284.
Hickling, Robert. 1962. “Analysis of Echoes from a Solid Elastic Sphere in Water.” The Journal of the Acoustical Society of America 34 (10): 1582–92. https://doi.org/10.1121/1.1909055.
MacLennan, D. N. 1981. The Theory of Solid Spheres as Sonar Calibration Targets. Scottish Fisheries Research Report 22. Department of Agriculture; Fisheries for Scotland.