harmonic sweep

[koolscooby]

Well okay, so this isnt really music, but i'm interested in recreating or finding the dolby digital (commonly used in) movies harmonic sweeping noise, i haev a program, goldwave, that lets me insert a function with incremental variables and constant variables, any audiophiles out there that know sound waves adn their functions? just curious

(Its a good sound to test speakers with imo )

merry christmas!

[wazzup]

Do u mean the THX intro?

[koolscooby]

Originally posted by wazzup
Do u mean the THX intro?

yeah i guess thats what it is

[Workhorse]

The "Expression Evaluator of Goldwave lets u to add desired Functions to Create Harmonics"

[koolscooby]

but i dont know the functions to create harmonics (thus i'm asking here hehe) ... i dont know the math for it

[IanHarvey]

You need to be able to calculate an amplitude y as a function of the time t in seconds.

Suppost you wanted a sine wave which started at 20Hz and swept upwards by 30Hz per second. You would do something like this:

y = sin( 2*pi*t * (20 + 30*t) )

(pi being 3.14159....)

This will give y's in the range -1 to +1; if this isn't right, and (for instance) the program expects numbers in the -32767 to +32767, you would adjust it to read:

y = 32767 * sin ( 2*pi*t * (20 + 30*t) )

If t isn't in seconds, you will need to adjust it accordingly e.g. if it's in CD samples, replace t with (t/44100) in the above equation.

Hope that gets you started...

Cheers
IH