What is Electrical Noise
Country: United States
Date: April 2008
What is electrical noise? Are there different types of
Electrical noise is any kind of electrical energy that you do not want.
For example, if you tune your radio to a place between two
broadcasting stations, you may hear some static or bleed through from
nearby stations. You may consider what you hear to be electrical
noise. Here is an example that may be more subtle. If you are listening
to music off your computer or media player, and there is a silent
passage in the music or between songs, you may hear some background
noise in the form of a hiss - this noise is inherent in electrical
devices. Good electronic products have components selected to minimize
this noise. The electrical content you want is called signal.
Electronic devices are often rated with something called a signal to
noise ratio. The higher the number, the better. Hope this helps.
The most broad definition of electronic noise, is the presence of
unwanted electrical signals that make it more difficult to detect or
process the actual signals one is interested in. An example of this is
an ordinary audio amplifier, such as that in cassette player. Very
weak signals are picked up from the moving tape, and fed to the
amplifier, which increases their strength sufficiently that these
signals can now drive a speaker or earphones.
With an amplifier such as this, electrical noise (or "noise" for
short) can result unwanted noise in the speaker of earphones. This
"noise" can come from inside or outside the amplifier. Many devices
such as fluorescent lights, computers, and many others, generate and
transmit unwanted signals. These signals may be picked up by the above
amplifier, and amplified together with the music from the tape. The
result can be a buzzing or other objectionable noise you hear.
In a television, the same sort of unwanted random transmitted signals
can cause speckles to appear and dance around on the TV screen,
messing up the picture.
Sometimes the components that are used to make the amplifier circuit
create electrical noise that can be heard in the speaker or earphones.
Components like transistors, used in an amplifier, are never "perfect"
and themselves can generate small amounts of random signals ("noise")
together with the signals they are supposed to be amplifying. This can
often be heard as a low level hissing noise in the speakers together
with the music.
Electrical noise, therefore is simply any unwanted electrical signals
that may be picked up from other equipment that is unintentionally
radiating (transmitting) them, or the unwanted signals can be
generated within the equipment by less than perfect components. We
call them "noise", because the effect is similar to how audio noise
prevents you from clearly hearing a sound or music you are trying to
Most generally, noise is any unwanted fluctuation in a reading. For example, a
circuit may have an intended signal -- say a voltage change -- but when you
actually measure the voltage, you may see fluctuations in the voltage. The
fluctuations are called 'noise'. If you graphed your voltage, instead of a smooth
straight line like you intend, it might be bumpy and bounce above and below the
You may also see a term called 'signal-to-noise', which is a measure of how strong
your signal is compared to how strong the noise is. If your signal is 100 times
stronger than your noise, the chances are good you will be able to detect the
signal. If your noise is just as strong as your signal, or stronger, then you may
have more trouble detecting the signal.
Hope this helps,
Click here to return to the Engineering Archives
Update: June 2012