Echo Sound Effect

Question

I am looking to build a a small program that reads a sound file and applies echo effect to it. I am seeking guidance for how to accomplish this.

Answer 1

For a simple echo (delay) effect, add a time-delayed copy of the signal to itself. You will need to make the sample longer to accommodate this. Attenuating the echo by a few dB (easily accomplished by multiplying individual sample values by a constant factor < 1) will make it sound a bit more realistic.

To achieve multiple echoes, apply the effect recursively, or set up a ring buffer with an attenuated feedback (add the output to the input).

For proper reverberation, the usual approach is to pre-calculate a reverb tail (the signal that the reverb should generate for a one-sample full-amplitude click) and convolve that with the original sample, typically with a bit of additional pre-delay.

There's a pretty concise book about DSP in general called 'Getting started with DSP'. Google it, there's a free online version.

Answer 2

I agree with the idea of delay and mixing,

but if you directly use a structure like that :

    ----<--------[low pass]-----
    !                          !
->-(+) ---[ delay line ]-------.--->

use multiple with different delays in parallel to create echo (low pass or other filters make that easyer but it's also that in reallity most of reflected signal spectrum is low, so it sound better. and serialized to decorrelate you signal (make that more realistic like the pysical diffusion of the sound).