Polyphony this may contain two or melodic voices, using different or chords. this is the most commonly used because most people are in bands, and some digital designed music also does the same. polyphony can use up 16 different notes at one time.
Sound spectrum is the frequencies measured in different levels, sound spectrum measures the strength of that signal and displays it on a graph.
Reverb is an effect in the acoustic environment that stimulates echoes in the sound signal. reverb can be set in different rooms the more reflective the walls are in the room the more reverb they will be in that room. church halls are a good example because a church choir sounds better in that room then if you put a rock band in it for example, because voices sound natural and reverb thickens the voices. were as reverb on some parts of the instruments in a rock band does not. The delay is short enough so our ears can't pick up the individual parts of it so it sounds like a sustained effect, this is because of reverberation
Echo is a more natural acoustic effect. and it is a results from reflections of that sound wave. It is a longer delay so we can pick out the individual parts of the echo so it sounds like we are sounds things over and over again. it the distance of sound traveled longer then 35 mili seconds then we get the echo effect
When the audience is in the venue, it wont sound the same if you sound checked it before. that is because humans are mostly water and fat, and are very good at absorbing sound. also if you was at the front of the crowd you are more likely to hear it to be louder, were as if you stood right at the back then you will hear it alot less then the ones standing at the front.
