Are articles needed in "sift signal from noise"? Is it the right word order?

Question

I have 2 related questions.

1. What is the correct expression in English? Is it with "the" or without it? In my research I have found roughly the same instances of both. If both are ok and there is a difference, could you explain it?

   • sift signal from noise
   • sift the signal from the noise

2. Does signal always go before noise? Why? In my research of examples that almost always seemed to be the case. Or can I invert the order as follows?

   • sift noise from signal
   • sift the noise from the signal

PS: I am referring to the figurative expression (and not to its literal usage in electrical engineering).

Answer 1

I initially thought that it ought to include 'the' in all cases, but in speech or scientific chat they could easily be dropped. However, I noticed as I'm typing this that I almost never actually want to use 'the' - perhaps as I'm not being specific as to which 'items' I am referring to.
If I said, "Once you have your audio sample, you then sift the signal from the noise." I'm now referring to one specific instance which needs sifting, and 'the' becomes far more appropriate.

You could argue that the order of sift x from y really depends on which you want to keep, but that's easily shown to not be true.

You sift lumps from flour - you discard what is left in the sieve, and keep that which falls through. As far as I'm aware this is the origin of the term, though ordinarily the lumps are not even significant to the process; you just sift the flour.

You sift signal from noise - but now you're keeping what's left over in your 'sieve' and discarding that which falls through.
One could perhaps argue that it ought to be 'sift noise from signal', so you discard the noise & let the signal fall through the sieve.

I think in this particular instance it may just be convention. We only ever talk about signal to noise ratio [SNR] & never noise to signal ratio, so maybe we are 'following form' in that we expect to hear the term signal first.

Answer 2

I am referring to the figurative expression (and not to its literal usage in electrical engineering).

Thanks for the context - it helps.

I would use "the" with both nouns as I also assume that the context includes an earlier reference to "what people are saying". i.e. the signal, and "the various imperfect ways they are saying it", i.e. the noise.

Does signal always go before noise?

Usually, (usually does not mean "always") the thing you want is the first item, unless the following sentence or clause refers to the unwanted item.

Answer 3

It could depend on context - are you speaking about the ability to separate these two things, or a specific instance of doing so?

'Signal' is a countable noun, so it needs an article if it is not plural. Although 'noise' can be non-countable, it should have a definite article in your example because it is specific noise that is being separated from the signal. You couldn't isolate and separate something from an abstract concept.

If you were talking about separating these two things in general, you should say:

You can separate signals from noise.

'Signals' is always countable, so it is a plural; noise can remain abstract because it is only possible that there may be noise.

If you are talking about a specific instance of this action, you should say:

You can separate the signal from the noise.

The definite article is appropriate as they are looking for a specific signal. If we are talking about radio signals, there are lots of signals everywhere, transmitted from all different places and on different frequencies. To receive or hear one, we have to isolate it, so you can see why they are countable.

I don't accept suggestions in other answers and comments that 'signal' can be non-countable, at least not in English grammar. Perhaps it is used that way as technical jargon in the field of radio communication, but if so, the majority of English speakers that do not work in that field may not recognise it. Many fields have their own terminology and it does not necessarily follow the rules of grammar. In my field of work, some English words are re-appropriated to mean something entirely different to their dictionary definitions.

Even if some related concepts can be non-countable - such as 'noise' and 'sound' - these are not the same as a 'signal'. Signals may be sent via mediums that are abstract, but that doesn't make them non-countable. It could be likened to the difference between 'a letter' and 'mail'. 'Mail' is non-countable and can refer to a single piece of correspondence, many pieces, all pieces, or the concept of sending correspondence. 'Letter' is always countable, even though you send letters through the mail.

As for which goes first... if 'sift' is actually the correct term for separating a signal from noise, then it doesn't really matter which goes first. Sifting is used to separate things. But it seems reasonable to keep 'signal' in first place as that is thing you want to keep. But it doesn't sound idiomatic to me.

I have some experience in audio production and the term I would use is filter. When you filter something, you remove it. So I would say I was filtering the thing I want to remove from the thing I want to keep, for example:

Filter out the noise from the signal.

Answer 4

sift signal from noise is fine.

Please refer to the man who wrote the most important book on communication theory.

A Mathematical Theory of Communication by Shannon and Weaver

• All of these changes in the transmitted signal are called noise.

signal and noise are concepts and do not require any determiner in phrases like sift signal from noise. Please see page 7 of the article: Message, channel, sender, receiver are all concepts in the theory.

Anyone interested in communication and translation should read this paper. Of course, there are times when one will use the signal, a signal or signals.

Why did we build this? It is increasingly challenging for security teams to sift signal from noise due to the overwhelming amount of security data generated by cloud infrastructure.

sift signal from noise

The Financial Times
Those are predictions from Black Swan, a London-based start-up that hoovers up data from social media, online forums, product review websites as well as other sources and then analyses it to divine what consumers want. Its artificial intelligence software purports to sift signal from noise to figure out which early trends are destined for mass adoption. Financial Times

Answer 5

I. Here's how sift works:

Sift the flour before mixing in the butter.

Sift X - X has to be your "haystack" normally, but if you want to talk about the "needle" you are looking for as well, the expression is *sift {needle} from {haystack}" (reference: https://idioms.thefreedictionary.com/sift+from) or "sift {needle} out of {haystack}"

So you would sift signal from noise, sift signal out of noise, but the thing you are actually sifting is the noise.

II. Here's how articles work:

What is the correct expression in English? Is it with "the" or without it?

When you say sift signal from noise, do you subjectively believe that the reader/listener should know which signal you mean? This may be true if you were talking about a signal earlier in conversation, or there is another reason. If so, use the.

If the reader/listener doesn't need to know or care which signal, then use a/an.

If "which signal?" is a question that doesn't make sense at all, because you are not talking about an actual signal, then don't use an article at all.