CmplxMultiply1

 

Cmplx = Complex

 

With complex numbers audio signals one can do strange things that cannot be done with normal real audio signals. One of these things is making a linear frequency shift (not to confuse with pitch shifting, where the spectrum is stretched or compressed). This linear frequency shift is done by a complex modulation or in mathematics called a complex multiply.

 

Can you insert normal real audio signals? Yes, but scale them always down with 0.707 (or 2 sqrt) or use only the left or right channel as input. The effect will be like a normal ring modulator: frequencies shift up and down at the same time. Most results will sound "dirty" or AM-like.

 

Can a real audio signal be made into a complex numbers audio signal? Yes, using a Hilbert transform.

 

Can a Hilbert transform be done on the Capybara? Yes with the HilbertTransform prototype Sound. Offline you could use for example Matlab. The original should be on the left channel and the Hilbert transformed version on the right channel. This is opposite for the HilbertTransform prototype, so swap L & R. Using this technique on a speech sample with this prototype will generate strange sounding speech signal (like a receiver not set to the correct frequency).

 

-- ChristiaanGelauff - 10 Mar 2007             Back one page