I have gotten the impression that questions shouldn't be marked as duplicates unless there is an answer to the question at hand in the original question. Is that correct?

I ask because of this question: What instrument produces a triangle wave?

The linked question that is (allegedly) a duplicate asks about triangle waves, but the only answer does not provide a single example of an acoustic instrument that produces a triangle wave-like sound. Specifically, the answer only relates string instruments to sawtooth waves and free reeds to pulse waves (which the answer calls "asymmetrical square waves"). Strangely, this accepted answer also does not discuss (symmetrical) square waves.

So is the triangle wave question a duplicate because the question is a duplicate, even though the original question does not contain an answer to the new question?

There is a comment on the alleged duplicate that says:

That linked question does include triangle wave sources. Closing as dupe

But for the life of me I can't find the supposed triangle wave sources in the answer or question.


Very first comment on that question:

Most of them :-). brass instruments are square waves (smoothed slightly by the instrument bore shape). Single reeds are close to triangle waves; bowed strings are sawtooth. – Carl Witthoft

Which answers the question perfectly. Sure - we could ask @CarlWitthoft to change the comment to an answer, for clarity.

  • Ah, I didn't pay attention to the comments. I had the impression they were ephemeral. Oct 5 '16 at 1:50
  • That is very true Todd. I'll get it converted to an answer.
    – Doktor Mayhem Mod
    Oct 5 '16 at 7:45

I put the newer question onto the dupe queue since I knew that the other question asked about triangle waves. I was working on the assumption that we would want to consolidate any relevant answers into that earlier question.

So my assumptions were:

  1. Closing based solely on the question, even if that question doesn't already have a good answer (for the newer question), and
  2. First come first serve: the earlier redundant question takes priority.

FWIW I'm unaware of any acoustic instruments that produce sounds close to symmetric triangle waves, or symmetric square waves for that matter, and nobody on this site has found one either.

  • Well, Carl seemed to. I haven't checked to confirm.
    – Doktor Mayhem Mod
    Oct 6 '16 at 22:20
  • @DrMayhem I'd reviewed Carl's comment. In the end it's somewhat of a judgment call (and depends on what exactly you measure), but for the waveforms/spectra analyses I've looked at, they don't fit the bill as being "close" to the mathematical ideal, in my judgment.
    – Dave
    Oct 6 '16 at 22:55
  • Ah - okay. That's better research than I had time to do.
    – Doktor Mayhem Mod
    Oct 6 '16 at 23:02

In general, you close based on the question. If they're truly the same question, then the answers will necessarily apply. (Whereas a particular answer can often be applied to very different questions.)

If the answers on the target are poor/don't answer the question, then they ought to be downvoted; you can only vote to close as a duplicate if the target question has an upvoted or accepted answer.

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