The purpose of audio/video recording is to capture sound from a source and reproduce it at the output of the microphone system.
The microphone and its SNR (Signal-to-Noise Ratio) are critical components in the sound recording signal chain, affecting the overall quality of the audio recording. The following table illustrates some typical use cases:
Microphone Capsule Signal-to-Noise Ratio Use Case Examples
In an open field, for every doubling of the distance, the sound pressure is halved (a decrease of 6 dB). The farther the sound source, the weaker the sound signal arriving at the microphone.
Since the self-noise of the microphone is constant, a decrease in the incoming signal level results in a reduced SNR of the microphone output signal.
Typically, weak signals must be amplified to reach an appropriate level in the device's signal path. However, amplifying the signal also amplifies any noise present in the output.
The more the signal is amplified, the higher the risk of noise rising to a level where it significantly degrades the quality of the captured signal.
Even if the signal is amplified, a high SNR microphone helps maintain low self-noise, ensuring that background noise is not heard. The greater the distance from the sound source, the more important it is for the microphone's self-noise to be low. This is especially crucial when the sound source is distant, and the signal itself is weak.
As the sound pressure decreases by 6 dB for every doubling of the distance, using a microphone with 6 dB higher SNR can double the capture distance without degrading signal quality.
POLQA (Perceptual Objective Listening Quality Assessment) is an ITU-T standard model that uses digital voice analysis to objectively assess the quality and clarity of recorded speech signals.
Microphones with high SNR perform significantly better in POLQA tests and provide excellent speech clarity. When recording with a higher SNR microphone, the same-sized signal appears much clearer.
