Display on TV and radios due to causes such as there being no signal
Noise in a CRT television (top) and flat screen television (bottom)
Noise
, commonly known as
static
,
white noise
,
static noise
, or
snow
, in
analog video
and
television
, is a random dot pixel pattern of
static
displayed when no transmission signal is obtained by the
antenna
receiver of
television sets
and other display devices.
Description
[
edit
]
The random pixel pattern is superimposed on the picture or the television screen, being visible as a random flicker of "dots", "snow" or "fuzzy zig-zags" in some television sets, is the result of
electronic noise
and radiated electromagnetic noise accidentally picked up by the antenna like air or cable. This effect is most commonly seen with
analog TV sets
, blank
VHS
tapes, or other display devices.
There are many sources of electromagnetic noise which cause the characteristic display patterns of static. Atmospheric sources of noise are the most ubiquitous, and include electromagnetic signals prompted by
cosmic microwave background radiation
,
[1]
or more localized
radio wave
noise from nearby electronic devices.
[2]
The display device itself is also a source of noise, due in part to
thermal noise
produced by the inner electronics. Most of this noise comes from the first
transistor
the antenna is attached to.
[2]
Names
[
edit
]
UK viewers used to see "snow" on black after
sign-off
, instead of "bugs" on white, a purely technical artifact due to old
405-line
British senders using positive rather than the negative
video modulation
used in Canada, the US, and (currently) the UK as well. Since one impression of the "snow" is of fast-flickering black bugs on a white background, the phenomenon is often called
myrornas krig
in
Swedish
,
myrekrig
in
Danish
,
hangyak haboruja
in
Hungarian
,
Ameisenkrieg
in
German
, and
semut bertengkar
in
Indonesian
, which all translate to 'war of the ants'.
It is also known as
ekran karıncalanması
in
Turkish
, meaning 'ants on the screen',
hangyafoci
'ant football' in
Hungarian
, and
purici
'fleas' in
Romanian
. In
French
however, this phenomenon is mostly called
neige
'snow', just like in
Dutch
, where it is called
sneeuw
. In
Portugal
, it's called
formigueiro
'anthill'.
In
Italy
this video noise is called
sale e pepe
'salt and pepper'. In
Argentine Spanish
it's called
lluvia
'rain', maybe related to the accompanying rustling sound.
[3]
Similarly, this noise is called
suna-arashi
'sand storm' in
Japanese
, referring to the natural phenomenon. In
Brazilian Portuguese
it's called
chiado
'wheezing', referring to the noise made by Brazilian pressure cookers.
Big Bang explanation
[
edit
]
Because analog television uses
radio waves
to carry information, some of the white noise is the television receiving microwaves from the
cosmic microwave background
, an important trace of the
Big Bang
. NASA describes, "Turn your television to an 'in between' channel, and part of the static you will see is the afterglow of the big bang".
[4]
[5]
This is also true for radio. When it is adjusted to a
frequency
that is between stations, part of the sound heard is remnant
radiation
from the Big Bang from around 13.7 billion years ago.
[6]
See also
[
edit
]
References
[
edit
]
Noise
(physics and telecommunications)
|
---|
General
| |
---|
Noise in...
| |
---|
Class of noise
| |
---|
Engineering
terms
| |
---|
Ratios
| |
---|
Related topics
| |
---|
Denoise
methods
| |
---|