A filter bag is used for filtering dirt, dust and other materials from the exhaust air flow of an upright vacuum cleaner, wherein an elongated, non-disposable outer fabric bag having a longitudinally extending delivery tube therein provides one stage of filtration and a disposable, inner paper filter bag provides a second stage of filtration. The filter bag construction may be used without the inner, paper filter bag when maximum filtration efficiency is not required or with the inner, paper filter bag when high filtration efficiency and/or the convenience of a disposable filter element are desired.

A filter bank is a collection of band-pass filters that separates the input signal into several components, each one carrying a single frequency sub-band of the original signal. It also is desirable to design the filter bank in such a way that subbands can be recombined to recover original signal. The first process is called analysis, while the second is called synthesis. The output of analysis is referred as subband signal with as many subbands as there are filters in filter bank. The filter bank serves to isolate different frequency components in a signal. This is useful because for most applications some frequencies are more important than others.

The filter cloth is usually made of nylon, terylene, or polypropylene which holds the solids. It is used for separation of solids and clear liquid filtration as in the cleaning of fuels or hydraulic liquids, or in water treatment. It is produced in many weave styles.