Definition of "underfilter"

It is clear that overfilters and underfilters are dual in the sense of the duality principle.

1999, Edward R. Dougherty, Jaakko Astola, Nonlinear Filters for Image Processing, page 180

The paving downstream consisted of 18x18x8-inch blocks laid on edge over a brick base which in turn was underlain with a gravel or brick chip filter. Since there was some controversy as to whether an underfilter was necessary, the first test was made with the filter omited.[sic]

1967, Journal of the Institution of Engineers Pakistan

Since there is no underfilter, the top flow line emerges on the downstream slope.

1988, Árpád Kézdi, László Rétháti, Handbook of Soil Mechanics, page 61

A single sheet of filter paper is used as an underfilter.

1992, Margaret M. Manson, Immunochemical Protocols, page 445

In addition, the flow from the underfilter, which had previously been clear, became cloudy, indicating that the filter had failed to block particles from the core.

2004, R.F. Craig, Craig's Soil Mechanics, page 430

It is not possible to overfilter your tank but marine aquaria are frequently underfiltered.

1966, William P. Braker, Know how to Keep Saltwater Fishes, page 19

You don't want to underfilter. Nor do you want to filter beyond what is economically justifiable.

1978, Hydraulics and Pneumatics

Underfiltering by using too high a cut-off frequency leaves too much noise in the reconstructed images (bottom row).

1994, Douglas Van Nostrand, Selected Atlases of Cardiovascular Nuclear Medicine, page 35