Noise Reduction

All recorded signals contain undesired noise in some form or another. Unlike noise control or soundproofing which actively deals with unwanted sounds in real time as they occur, the process of noise reduction involves removing noise from an analogue or digitally recorded signal. (This can also be done in real time, but the benefits of treating a recorded sound means audible noises can be targeted with specific reduction techniques over and over).

Noise contained within a signal can be randomly generated by devices or equipment. It can also be ‘white noise’ an audible background static buzz made of all the frequencies within the audio spectrum.

A major form of undesired noise in electronic recording devices is this buzz, or hiss. It is caused by electrons reacting to the resistance heat within the equipment and deviating from their normal path within the current flow. Since electron flow is what determines the voltage output level, indiscrepancies in the uniform flow will cause digressions in the voltage output, and create unwanted noise in the form of hiss.

The techniques for noise reduction are independent of the signal being processed, implying that all the techniques are very similar, and will work on all signals. However knowledge of the signals’ characteristics will influence the variations of the technique which must be implemented to best remove the wanted noise. Analogue signals are different from digital, and must be treated as such.