This MATLAB exercise enables the user to introduce a reverberation or a simple echo into a speech or audio file in order to investigate the effects of echo delay and echo amplitude on the perception of the resulting echoed signal. If the original signal is designated as x[n], the echoed signal is of the form y_e [n]=x[n]+∝x[n-N], where the relevant echo parameters are ∝, the echo gain, and N, the echo delay (in msec), as specified in the exercise user interface.