# Signal to Noise Ratio: Questions for my multimedia and signals class

1. May 12, 2010

### Whoohw

Question one
1. The problem statement, all variables and given/known data
x[n] = 5sin(0.22*pi)
The root mean square (RMS) value eof a sin wave is known to be A/root(2) where A is the amplitude. If the noise in a system is known to have an RMS value of 0.5, what si the signal to noise ration (in dB) of the x[n] in this syetem.

2. Relevant equations
RMS = A/root(2)
SNR = (Asignal/Anoise)^2
SNRdB = 10log10(SNR)

3. The attempt at a solution
Well, i figured that "A" for the RMS given (0.5) is root(2)/2

However, i do not know that which A is Asignal and which is Anoise (root(2)/2 or 5*sin(.22*pi) or just 5).

2. May 12, 2010

### Staff: Mentor

Shouldn't the formula above have n on the right side? Otherwise, all your values of x[n] are exactly the same.

3. May 12, 2010

### Whoohw

Thats what I keep thinking, but i that isnt what the problem has in the notation.

4. May 12, 2010

### Staff: Mentor

Then I'd be willing to bet that it's a typo. Otherwise you don't have a sine wave. In that case x[n] is equal to about 3.1871 for all n. IOW, it's constant.