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26th December 2003, 01:08 AM  #1 
diyAudio Member

harmonic sweep
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!
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Brad 
30th December 2003, 10:03 PM  #2 
diyAudio Member

Do u mean the THX intro?
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"I`m not the messiah!" 
31st December 2003, 02:19 AM  #3  
diyAudio Member

Quote:
yeah i guess thats what it is
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Brad 

31st December 2003, 03:02 AM  #4 
diyAudio Member
Join Date: Dec 2004

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

31st December 2003, 06:35 PM  #5 
diyAudio Member

but i dont know the functions to create harmonics (thus i'm asking here hehe) ... i dont know the math for it
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Brad 
8th January 2004, 05:05 PM  #6 
diyAudio Member
Join Date: Apr 2003
Location: Cambridge, UK

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 
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