In signal processing, there are many instances in which an input signal to a system contains unnecessary content or additional noise which can degrade the quality of the desired signal. In such cases, the useless samples may be removed or filtered out. For example, in the case of the telephone system, there is no reason to transmit very high frequencies since most speech falls within the band of 400 to 3,400 Hz. Therefore, in this case, all frequencies above and below that band are filtered out. The frequency band between 400 and 3,400 Hz, which isn’t filtered out, is known as the pass band, and the frequency band that is blocked out is known as the stop band.

FIR, Finite Impulse Response, filters are one of the primary types of filters used in Digital Signal Processing. FIR filters are said to be finite because they do not have any feedback. Therefore, if you send an impulse through the system (a single spike) then the output will invariably become zero as soon as the impulse runs through the filter.

The frequency response of four low pass FIR Filters with cutoff frequencies of 2 kHz, 4 kHz, 6 kHz, and 8 kHz are shown in figure 1

Figure 1: Frequency response of low pass FIR filters

There are a few questions related to the experimental observations at the end of the experiment.