Calling all sound engineers! Hello all, In my college physics course we are currently going over sound waves. I was excited to learn some of the science behind the loud noises I can make with my instruments. Specifically, I wanted to know if anyone knew exactly what cranking up 'Intensity' knob does to one's tone- in scientific terms of course. The definition of intensity as explained in lecture and via the exam formula sheet is Intensity = Power/Area or simply, I=P/A. From there, I can safely assume that the size of the speaker projecting the instrument's signal cannot increase (A is constant). Thus, when a musician turns up the intensity knob on their controls, the amount of watts sent to the speakers (the power P in watts) is increased, but this does not necessarily mean an increase in volume- it is just going from clean tone to a more distorted one right? Though in the other respect, I could see the increased intensity increasing volume as beta (in decibals)= 10dB x log(I/I[SUB]0[/SUB]). Where I= new intensity and I[SUB]0[/SUB] equals the reference intensity. Do I have the right idea or can some one tell me what's what with this stuff? My lecture professor is not a musician so he is curious about this as well. I searched all over the web and wasn't able to find an explanation on any forums, wikis, or guitar amp websites. Thanks! Ryan Side note: I realize we do not see many 'Intensity' knobs on bass amps- the only ones I have seen were on old Fender guitar combos and reissues- any one have a bass head with such a control? EDIT: Okay, I think I've got this all figured out. The physical/scientific definition of intensity has nothing to do with the intensity knob on amplifiers- such knobs are only related to the on board-vibrato effect some amps sport. The physical intensity I want to talk about actually relates to the amplifier's volume output. Loudness is given by beta (in decibals)= 10dB x log (I[SUB]1[/SUB]/I[SUB]0[/SUB]) where I[SUB]0[/SUB] = 1.0 x 10[SUP]-12[/SUP] W/m[SUP]2[/SUP] and I[SUB]1[/SUB] = the I value obtained by I=Power (in watts)/area (in m[SUP]2[/SUP]). That very last formula can be simply stated by I=P/A. <if any one really cares to see, I could show how much an increase in power would effect volume on a particular cab, I just don't have the time to think of an example myself at the moment> Moving to the 'intensity' knobs on amplifiers- I can see it doing one of two things (sorry, I haven't had a chance to check out any of the links you guys have posted). 1) The knob can increase the presence of the effect; that is, lets say you have a clean tone (dry signal) and you wish to add vibrato (wet signal). Cranking this knob will increase the amount of vibrato present in your sound. 2) The knob will increase the rate of vibrations in your vibrato tone (See: surf music haha). I guess all of this leads me to more questions about the way effects pedals can visually change a wave of sound. I'll do some looking on the internet but I also would like to do some recording myself- garage band (my only recording program) shows the waves on screen. I think it'd be a cool project to play the same tune with clean, distorted, vibrato and see the visual differences between each. I know my professor is pretty interested in it- I'll post my results if any one cares to take a look.