Signal To Noise Ratio

Discussion in 'Hobby Electronics' started by Allan, Jul 5, 2006.

1. Is the better signal to noise ratio the larger or smaller? For
instance - 80 or 100dB?

2. David L. JonesGuest

The larger the number the better.

100dB means the signal level is 100000 times larger than the noise.
80dB means the signal level is 10000 times larger than the noise.

Here is some info:
http://en.wikipedia.org/wiki/Signal-to-noise_ratio

Dave 3. Alan RutlidgeGuest

Err Dave, this some New World maths?

Last time I checked, a 60dB power ratio was 1,000,000 : 1
70dB = 10,000,000 : 1
80dB = 100,000,000 : 1
90dB = 1,000,000,000 : 1
100dB = 10,000,000,000 : 1
0dB = 1 : 1
3dB = 2 : 1
10dB = 10 : 1
20dB = 100 : 1
30dB = 1,000 : 1

It's a logarithmic ratio. Get the picture?

The formula is dB = 10 log(base10) Ps/Pn; where Ps and Pn represent the
signal and noise power levels respectively.

When comparing voltages (where the impedances are the same) the formula of
dB = 20 log(base10) Vs/Vn ; where Vs and Vn represent the voltages of the
signal and noise levels respectively.

Cheers,
Alan

4. David L. JonesGuest

My figures are correct for a voltage ratio.
By saying "signal level" I was implying the voltage levels, sorry,
thought that was obvious. I didn't want to go into impedances.

The link I posted shows both fomula. Hopefully the OP wasn't too
confused. For a beginner, voltage levels would be easier to understand
than power levels.

Dave 5. power
10dB = x10

voltage
20dB = x10

simple

: Alan Rutlidge wrote:
: > : > > Allan wrote:
: > >> Is the better signal to noise ratio the larger or smaller? For
: > >> instance - 80 or 100dB?
: > >
: > > The larger the number the better.
: > >
: > > 100dB means the signal level is 100000 times larger than the
noise.
: > > 80dB means the signal level is 10000 times larger than the noise.
: > >
: > > Here is some info:
: > > http://en.wikipedia.org/wiki/Signal-to-noise_ratio
: > >
: > > Dave : > >
: >
: > Err Dave, this some New World maths?
: >
: > Last time I checked, a 60dB power ratio was 1,000,000 : 1
: > 70dB = 10,000,000 : 1
: > 80dB = 100,000,000 : 1
: > 90dB = 1,000,000,000 : 1
: > 100dB = 10,000,000,000 : 1
: > 0dB = 1 : 1
: > 3dB = 2 : 1
: > 10dB = 10 : 1
: > 20dB = 100 : 1
: > 30dB = 1,000 : 1
: >
: > It's a logarithmic ratio. Get the picture?
: >
: > The formula is dB = 10 log(base10) Ps/Pn; where Ps and Pn represent
the
: > signal and noise power levels respectively.
: >
: > When comparing voltages (where the impedances are the same) the
formula of
: > dB = 20 log(base10) Vs/Vn ; where Vs and Vn represent the voltages
of the
: > signal and noise levels respectively.
:
: My figures are correct for a voltage ratio.
: By saying "signal level" I was implying the voltage levels, sorry,
: thought that was obvious. I didn't want to go into impedances.
:
: The link I posted shows both fomula. Hopefully the OP wasn't too
: confused. For a beginner, voltage levels would be easier to understand
: than power levels.
:
: Dave :  