Sound levels in frequencies ranging from 500 to 2500 Hz are more audible to humans compared with frequencies below 100 Hz. Consequently, the A-weighting scale was developed to measure sound levels in units of dBA to simulate the hearing response of humans. Under this weighting system, the sound pressure level at low frequencies is reduced based on its audibility to humans. The linear (no weighting) and C-weighting scales are often used to determine the relative contribution of low frequency sounds during a sound measurement. These low frequency sounds may not be audible to humans hence the use and wide acceptance of the A-weighting network. Figure 1 provides a graph that shows the reduction by frequency for A- and C-weighting scales.