Many the system which only allows signals
Many externalcauses in transmission system and other environmental factors are the sourcesof noise produced (Nalin, 2014).
For example, the increased use of industrialequipment such as fans, engines, ventilators and compressors has causes theproblem of noise in industrial environments (Kang, Moon, and Lim, 2014). Mostmanufacturing noise is variable or intermittent (Canadian Centre forOccupational Health and Safety CCOHS, 2015). According to CCOHS (2015), noiseis irregular when the environment is mixed with noisy and quiet periods. Forinstances, impact noise produced from the car collision in a quiet environmentproduces a short period of loud noise (Pulsar, 2005).
Insignal processing, a filter is a device or process that removes unwantedcomponents or features from a signal (Revolvy Discuss, n.d.). Filtering is aclass of signal processing with the complete or partial suppression of someaspect of the signal (Douglas, 2017).
In other words, Douglas’s statement meansthat filtering can be used suppress and reduce background noise by removingcertain frequencies in the signal. Filters are widely used in electronics andtelecommunications (Chang, Zhang, and Huang, 2011). For examples, filters areused in television, radar, control system, radio, music synthesis, imageprocessing, audio recording and computer graphics. Ideal filtering system is the system whichonly allows signals within certain range of frequencies to pass through whileblocking the others (Kelsey and Aschliman, 1994).
Ideal filter can becategorized into low-pass, high-pass, band-pass and band-stop. The selectivityof filtering technique used is based on the desire output of the applicationsince different filtering technique produce different output.Low-passfilter is a filter that passes signals with the low frequency than the cut-offfrequency and blocks signals with frequencies higher than the cut-off frequency(Makandar and Halalli, 2015). The cut-off frequency is depended on theapplications. There are different types of low-pass filter, which include,ideal low-pass filter, Butterworth low-pass filter and Gaussian low-pass filter(Shi, 2011). According to Shi (2011), an ideal low-pass filter is the simplestlow-pass filter which blocks all high frequency signals with greater distancethan the specified distance from the origin. The transfer function of an ideallow-pass filter is: where D(u, v)is the distance from point (u, v) to the center of the frequency.
Accordingto (Kevan, 2004), Butterworth low-pass filter is a design of frequency-domainfilter to remove high-frequency noise with minimal loss of signal components inthe specified pass-band with order n; Forthe Gaussian low-pass filter, the transfer function is as follows (Kevan, 2014): Forhigh-pass filter, signals with the frequency above the cut-off frequency is toallowed to pass through while signals with frequency lower than that will beblocked. High-pass filter can be expressed in terms of low-pass filter where is the high-passfilter while is the low-passfilter:Furthermore,band-pass filter is a filter that passes signals within the range of thecut-off frequencies set (Vigneshwaran, Santhoshkumar, and Srikanth, 2016). Toachieve band-pass filter, a signal should processed through high-pass filter,amplifier and low-pass filter as shown in Figure 2.1 below.