Mechanisms of effect of background noise when using microphoneand can be different. In most cases, the causes of this phenomenon lie not so much in the microphonee, as in the intermediate electrical circuits and devices through which the audio signal.One of the most frequent reasons for the emergence of a stable low-frequency background is the connection of a passive microphone (without built-in pre-amp) to the radio is not shielded cable. In this case, the background due to the emergence of the induced voltage, comparable in amplitude with the signal of the microphoneand, from consumer lighting networks. The frequency of the background, respectively, equal to the frequency of the mains voltage (50 Hz). To avoid such problems, you need to use to connect the microphoneand braided cable. The braided cable should be connected to the "body" (a zero power circuit) of the amplifier.Background caused by interference from household electrical networks, can occur when using shielded cable. Often the background is shown only when you touch the enclosure or separate metal housing components microphone. This means that the signal cable has lived a galvanic connection of these parts. The background signal is induced in the human body and in contact with the microphoneohms input amplifier.Source of interference can be various home appliances, e.g. mobile phones. Often this background is evident not constant, and periods of various duration (subject to certain subsystems of the devices). The induced electrical oscillations of audible frequency range, typically are multiples of harmonics of the original RF signal, or the result of dividing the low-frequency component of the filter formed by the parasitic inductance and capacitance of the cable connecting the microphone.