Maths clarification (to do with complex numbers)

Psyk · 17 Apr 2007 at 20:13

I'm following a tutorial about beat detection for music and I was slightly confused about this sentence:

"From the FFT we obtain 1024 complex numbers. We compute the square of their module and store it into a new 1024 buffer."

What does it mean by the square of their module? Is the module just the absolute value of the complex number, ie. sqrt( Re(z)^2 + Im(z)^2 ) ?

I can follow the rest of it, it's just I'm not quite sure of the terminology here.

Visage · 17 Apr 2007 at 20:19

Psyk said:
I'm following a tutorial about beat detection for music and I was slightly confused about this sentence:

"From the FFT we obtain 1024 complex numbers. We compute the square of their module and store it into a new 1024 buffer."

What does it mean by the square of their module? Is the module just the absolute value of the complex number, ie. sqrt( Re(z)^2 + Im(z)^2 ) ?

I can follow the rest of it, it's just I'm not quite sure of the terminology here.

Yup. Thats exactly what they mean. mod(x + iy) = sqrt (x^2 + y^2)

DAVEM · 17 Apr 2007 at 20:19

Psyk said:
I'm following a tutorial about beat detection for music and I was slightly confused about this sentence:

"From the FFT we obtain 1024 complex numbers. We compute the square of their module and store it into a new 1024 buffer."

What does it mean by the square of their module? Is the module just the absolute value of the complex number, ie. sqrt( Re(z)^2 + Im(z)^2 ) ?

I can follow the rest of it, it's just I'm not quite sure of the terminology here.

Must admit not familiar with that here!

Can only think of modulus here?

daz · 17 Apr 2007 at 20:19

I'm pretty sure they must mean the modulus, so you're right.

Amleto · 17 Apr 2007 at 20:19

think so.

the 'modulus' is the length of the complex vector.

Psyk · 17 Apr 2007 at 20:28

Ah I see. Is module the plural of modulus? That would make sense.

Thanks for the help everyone.

Inquisitor · 17 Apr 2007 at 20:31

Psyk said:
Ah I see. Is module the plural of modulus? That would make sense.

Thanks for the help everyone.

Nope, moduli is the plural

Can't think why they'd call it the module :confused:

Arcade Fire · 17 Apr 2007 at 20:51

I assume that the point is to calculated the average energy of a sample; in that case after you've done the FFT the next step is to take the squares of the moduli of the output. They must mean moduli instead of module; it doesn't make any sense otherwise.