output .the imperfections in the signal source is automatically compensated for and accommodated
for example ,a filter is being tested from 1 to 2 KHz. the input signal is exactly 1 V at all frequencies. the measured filter output over the range of interrest is shown in figure 3.2 .Also shown is the dB attenuation at each frequency. Next, the same filter is tested, but with a signal generator that has nonflat output. The filter input values over the band of interest are shown in figure 3.3 The measured filter outputs are indicated in the next column. the calculated response of the filter is in the last column. Note that the result is the same, even though the absolute values of the inputs were not identical to the first case. Anyone using this chart would know that their input signal at 1500 Hz would be attenuated by 3 dB regardless of the actual input voltage (as long as the signal was not so large that it overloaded the input and caused the filter output to saturate