People often use the term 'static' or 'static noise' to describe the sound of an untuned radio - which is more accuractely called white/pink/brown noise depending on the frequencies present.
I'm curious as to why it's called 'static'. What's unchanging?
From wikipedia all I could see was:
Alternatively, the use of an FM radio tuned to unused frequencies ("static") is a simpler and more cost-effective source of white noise
The Wikipedia article is, um, not as technically correct as it could be.
FM interstation hiss should not be called static. FM interstation hiss is not really accurate white noise (equal power at all frequencies) either, although it comes close.
True "static" wrt radio reception usually does not happen on FM, at all. (It can, if the source of the interference is extremely strong, or if the FM receiver's "AM rejection ratio" is poor, but this is uncommon.) It happens on AM.
It is indeed caused by discharges of static electricity - hence the name - mostly in the upper atmosphere. This noise was called "static" long before Edwin Howard Armstrong developed FM radio, in a successful quest to vanquish the noise.
The term is apt: If you tune an AM radio to an unused frequency, and then shuffle across the floor and touch a doorknob - or separate two dissimilar fabrics, fresh from the dryer, from each other - or pet a cat - ideally all in cold dry weather - you will produce static discharges (some big enough to see and feel as sparks), and you will hear pops and clicks in the radio speaker that are exactly like the rest of the "static" you hear on AM, except in intensity.
( Heck, Heinrich Hertz first created the first (known) human-generated radio waves in exactly this manner, by making sparks. I say "known" because people have obviously been making static discharges for forever, but we didn't know they produced electromagnetic waves - radio waves - until then. "Spark-gap" transmitters were all we had until rotary alternators came along. (Tesla's patents that are supposedly for "inventing radio" concern the rotary alternator, which was later improved on by Alexanderson.) )
So - why is FM interstation hiss called "static"? In technically correct usage, it isn't. In common use, though, when FM came along, people didn't distinguish between the hiss heard on an untuned FM receiver and the "static" pops and clicks from AM. They just knew that the latter had been called "static", and so in popular usage this was generalized to "noise from a radio receiver (and, later, TV receivers) when tuned to a weak or no station".
Static noise in a receiver is produced by static electrical charges, i.e., stationary charge, the kind not running in a circuit.
Why is white noise called 'static'?
OP refers to the sense of static employed in physics, where it represents electrical interference. My intuition is that we refer to noise, or white noise as static because it interferes - disrupts, distorts and obscures - the data or information we are trying to focus on, which is a cause of aggravation.
How static came to be used in this sense I don’t know. I could only find this brief entry on its etymology, but the figurative sense therein seems dispositive.
static (n.) "random radio noise," 1912, from static (adj.). Figurative sense of "aggravation, criticism" is attested from 1926.
interference noun: 1. the action of interfering or the process of being interfered with. 2. Physics the combination of two or more electromagnetic waveforms to form a resultant wave in which the displacement is either reinforced or canceled.
• the fading or disturbance of received radio signals caused by unwanted signals from other sources, such as unshielded electrical equipment, or broadcasts from other stations or channels.
synonyms: disruption, disturbance, distortion, static
white noise noun: 1. (General Physics) a. sound or electrical noise that has a relatively wide continuous range of frequencies of uniform intensity. b. noise containing all frequencies rising in level by six decibels every octave.
noise noun: 2. technical irregular fluctuations that accompany a transmitted electrical signal but are not part of it and tend to obscure it.
• random fluctuations that obscure or do not contain meaningful data or other information. "over half the magnitude of the differences came from noise in the data"
In general, 'noise' can refer to anything that interferes with what we want: it might be a single voice of someone sitting next to us in a movie.
Any kind of filtered noise signal can be called 'colored noise', which is just to say that it is not a pure white noise. In audio, the most common color encountered is 'pink noise': Realized as sound, white noise sounds like the hiss of an untuned FM radio, or the background noise on a cassette tape player. Because of the particular characteristics of the human ear, the sound of white noise is dominated by the very highest frequencies.
It commonly is referred to as "static" because, as explained in earlier posts, the term has been used regularly in the context of "the sound heard from a radio tuned to an unoccupied channel", it is considerably more concise than that preceding phrase and it is generally understood to have that meaning. In truth, even in the original context of AM radio reception of noise from electro-static discharges, the term "static" is erroneous because in order for a discharge to occur, the (previously) static charge must move and is therefore no longer static. So in the original context, the term "static" was an abbreviation for "electro-static discharge".
I am pretty sure I have the answer because I remember when I first noticed people mistakenly calling white noise static.
When a CRT TV with a built in analog tuner would have it's antenna disconnected or on a channel with no tower transmitting on that frequency you would hear the white noise and see the black and white scrabbled picture. The TV is unusable in this state so, when people would turn on a TV and encounter this they would often turn the TV off. Turning a CRT TV off make the tube act as a Van de Graaff generator sending positively charge ions to the front of the screen: static. If you touched it with your hand you would then pull these ions into your body which would have more negative ions since you are standing on the ground. As a kids my siblings and I would also sometimes place our heads against the TV to get these ions in our hair to make it stand on it's end. When you touch the TV tube with these ions a faint crackle sound or "static sound" is heard. The static sound was not too different from the white noise you had just heard from the lack of an antenna signal when the TV was on. Thus, the association between white noise, a term not in the vocabulary of the general public (while static was), and the noise of static electricity transfer to a body, was made. Obviously the static sound was a short burst while the white noise is constant, but the association still stuck.
