S / N ratio
The dimensionless signal-to- noise ratio , symbol D g , is one of the most important electroacoustic properties of a transmission system for acoustic signals. It is the ratio between noise and useful voltage , is determined on a logarithmic scale and given in dB :
- U g = noise voltage (e.g. in volts )
- U n = useful voltage (e.g. in volts) as a reference value
The measurement of the noise power is made via a weighting filter , the frequency dependence of the ear sensitivity is adjusted (see curves of equal volume level ) and, depending on the transmission system ( radio or telephone differs).