tremolo

Hi Guys, 

Need some explanation here, 

D = Depth 
et= envelope 

et = 1 + D sin (2*pi*fm*t); 
y(n) = et * sin (2*pi*fc*t) 
     =( 1 + D sin (2*pi*fm*t)) * sin (2*pi*fc*t) 


So, 

to get the tremolo effect, which of the following is the right one 

1.Tremolo = ( 1 + D sin (2*pi*fm*t)) * audio signal 

or 

2. Tremolo = ( 1 + D sin (2*pi*fm*t)) * sin (2*pi*fc*t) * audio signal 


p.s- there are some people saying it's not supposed to be 2Pi,because you
would get double frequency than expected

so, which one is which?

Please advice

On Apr 7, 10:51&#4294967295;am, "chinglnc" <ching...@hotmail.com> wrote:
> Hi Guys,
>
> Need some explanation here,
>
> D = Depth
> et= envelope
>
> et = 1 + D sin (2*pi*fm*t);
> y(n) = et * sin (2*pi*fc*t)
> &#4294967295; &#4294967295; &#4294967295;=( 1 + D sin (2*pi*fm*t)) * sin (2*pi*fc*t)
>
> So,
>
> to get the tremolo effect, which of the following is the right one
>
> 1.Tremolo = ( 1 + D sin (2*pi*fm*t)) * audio signal
>
> or
>
> 2. Tremolo = ( 1 + D sin (2*pi*fm*t)) * sin (2*pi*fc*t) * audio signal
>
> p.s- there are some people saying it's not supposed to be 2Pi,because you
> would get double frequency than expected
>
> so, which one is which?

2 is likely wrong.  it would be a complex tremelo if it were.

1 looks correct if |D|<1 and you need the 2 pi if fm is in Hz.

r b-j