The supersonic intensity is a quantity that represents the net acoustic output that a source couples into the medium; it can be regarded as a spatially low-pass filtered version of the active intensity. This spatial filtering can lead to significant error due to spatial truncation. In this paper, based on a space-domain formulation of the problem, the finite aperture error is analyzed and examined experimentally. The results indicate that the finite aperture error can be mitigated with the appropriate processing and that the supersonic intensity provides a valid quantitative representation of the effective radiation of acoustic sources.
Fernandez Grande, E., & Jacobsen, F. (2014). Conservation of power of the supersonic acoustic intensity. Journal of the Acoustical Society of America, 136(2), 461–465. https://doi.org/10.1121/1.4887446