How can I measure a sudden increase in the volume of an audio source(to create a music visualizer like effect)
You already got some answers in your previous threads on the topic:
url=http://forum.unity3d.com/threads/67307-Dynamic-audio
url=http://forum.unity3d.com/threads/68152-AudioSource.GetOutputData
In short, you’ll have to analyze the output somehow and adjust the visuals accordingly. Analyzing digital audio data isn’t trivial in general, but if you just want to respond to average volume/intensity, you could try averaging the sample values over some time period and then responding to the average value. (Just guessing though - I haven’t tried anything like that myself.)