Digital filters are mandatory for digital signal processing. This paper presents digital filter dispelling the unwanted signals or noise from the required signal and enhances the better performances of the signal. The extracted features of the digital filter have been analyzed to acquire the better output of the signal by using IIR Butterworth filter. It provides different designed parameters of IIR filter to achieve the desired result. MATLAB FDA tool is considered to find out the different responses of a digital filter. About eight parameters like-Phase response, Magnitude response, Magnitude & Phase response, Step response, Group delay, Pole/Zero Plot, Phase delay, Impulse response are used to analyze the filter responses. Some selected audio signals are used for observing the empirical response of high pass, low pass, band stop filter and band pass filter. A special tool is developed for this observation purpose.