Audio steganography

My graduate work is to make research into a part of information security which is called information hiding.
I use echo signals for embedding a digital watermark into an audio signal. It might be any music, songs , speech and so forth. For example, we can use two echo signals with different delays.  People's ears can't recognise recognize echo when delay is very short, but there are two contradictory factors.
The more amplitude the echo is has, the better for our system, becouse because extracting is mor easily easier. On the other hand, a large amplitude affects sound quolity quality. For instance, when the amplitude is too big, it's possible to hear some sizzle and other distoration distortion of music.
There are many contradictoring factors, and one of my purposes is to find balance between them.
In conclusion, let me say that there is much work to do in this area, and I hope I will have done at least small part of it when I end my time at the university.

(American English help)