The noise, or noise floor also English, referred to the intrinsic noise of a single device such as an amplifier stage or a measuring device, which is only in working order, but no useful signal leads. For encoders causes the level of the background noise that signals with lower levels can no longer be detected. The noise represents a lower limit of resolution is, in this case, the signal -to-noise ratio ( SNR) is equal to 1
The noise floor has perceived resemblance to the white noise and is accordingly. The noise is caused by several factors. One factor that strongly influence the strength of this noise takes is the type of device, whether it is an active or a passive device. For passive components, the noise is caused by the Brownian motion, the thermal noise. For active devices the cause is seen in the power supply. The more power a device needs to provide, the greater may be the noise.
Another factor is the temperature in the device and around the device. The higher the temperature, the greater the self-movement of the particles (electrons, protons, neutrons ). Furthermore, the mechanical and electrical shielding exert enormous influence on the behavior of the background noise. A further point is influencing the nature of the construction of the device. If many components installed inside or only the most important. The more resistors and capacitors are installed, the greater the noise floor will be. Is the total resistance of a circuit is halved, then the noise is reduced by about 3 dB. This should however be noted already in the design of the device, since a subsequent change only with difficulty and with increased effort. Furthermore, the intensity of the noise depends on the composite devices. At the end of almost every transmission chain is a playback device in the form of a loudspeaker or earphone, which is driven by an amplifier. The higher the gain, the more significant the noise is noticeable.
Opportunities to reduce
To keep the noise as low as possible and to reduce the audibility of a playback system, there are again many possibilities. Firstly, it is recommended to expose the equipment not greater heat, especially in summer, or to affect the cooling of the active components. Another possibility would be the use of expanders and gates, which reduce or hide by the working of the device is artificially changed the background noise. Another option is to cover the noise floor by means of the useful signal.
The noise floor can always be perceived, such as when the stereo is turned on, without playing a CD or cassette. Not always it is disturbing or intrusive.
The noise floor is the lower end of technical transmission range of the device Represents the means that they exceeded noise level ( the useful signal is louder than the background noise ) the system dynamics starts. For the system dynamics, the term signal - to-noise ratio also may be used.