(S/N Ratio) In any communication system the ratio of the signal to noise power, the S/N ratio, available to drive the audio or video device is the central factor in determining whether a communication signal is usable. Even when the noise power is quite high, if the signal power is sufficient the S/N ratio and thus picture quality can be acceptable.bjective experiments have shown that television picture quality is directly related to the S/N ratio. For example, in 1959, the FCC in the United States, authorized a task group, known as the Television Allocations Study Organization or TASO, to investigate the problems associated with television broadcasting and reception. When a standard television set was viewed by people who were then asked to rate picture quality results indicated that for an acceptable picture a S/N ratio of at least 35 dB was necessary. Other studies have confirmed these findings.