The clear pick-up of quiet, distant sounds by a microphone due to a high S/N ratio. See self-noise. The higher the SPL of the sound source at the mic, the higher the S/N ratio. Given an SPL of 94dB, a S/N spec of 74dB is excellent, 64dB is good. The higher the S/N ratio, the cleaner (more noise-free) is the signal, and the greater the reach of the microphone.