How to generate realistic echo to sounds?

1. What is echo sound effect?
2. How to generate echo signal in matlab?

What is echo sound effect?

Echoes are sounds that are delayed far enough in time so that you hear each as a distinct copy of the original sound. When reverb or chorus might muddy the mix, both delays and echoes are a great way to add ambience to a track.

How to generate echo signal in matlab?

The function is to be called like this: output = echo_gen(input, fs, delay, amp); where input is a column vector with values between -1 and 1 representing a time series of digitized sound data.