MATLAB TUTORIAL-2

                  Effects of the the echos in MATLAB 

HELLO FRIEND'S,

 here i have posted the code which paste in the matlab and enjoy the echo effect in music processing,do it yourself and understand what is really effect of the echos.

Echo Generation The most basic of all audio effects is that of time delay, or echoes. It is used as the building block of more complicated effects such as reverb or flanging. In a listening space such as a room, sound waves arriving at our ears consist of direct sound from the source as well as reflected off the walls, arriving with different amounts of attenuation and delays. Echoes are delayed signals, and as such are generated using delay units. For example, the combination of the direct sound represented by discrete signal y[n] and a single echo appearing D samples later (which is related to delay in seconds) can be generated by the equation of the form (called a difference equation)

                                                     x[n] = y[n] + αy[n − D], |α| < 1

where x[n] is the resulting signal and α models attenuation of the direct sound. Difference equations are implemented in MATLAB using the filter function. Available in  MATLAB is a short snippet of Handel’s hallelujah chorus, which is a digital sound about 9 seconds long, sampled at 8192 sam/sec. To experience the sound with echo in (1.2), execute the following fragment at the command window. The echo is delayed by D = 4196 samples, which amount to 0.5 sec of delay.

CODE:-

                load handel; % the signal is in y and sampling freq in Fs
                sound(y,Fs); pause(10); % Play the original sound
                alpha = 0.9; D = 4196; % Echo parameters
                b = [1,zeros(1,D),alpha]; % Filter parameters
                x = filter(b,1,y); % Generate sound plus its echo
                sound(x,Fs); % Play sound with echo

You should be able to hear the distinct echo of the chorus in about a

half second.