I create a math game where the user has to solve an equation. If the user is right, the application plays sound A. If he's wrong, it plays sound B.
What criteria should I use to choose sounds for A and B?
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Sign up to join this communityGood sounds are generally higher pitched and more crisp than bad sounds.
It depends on the tone of your game.
If it is humoristic, you can probably go with a 'ta-daaaa!' trumpet sound for correct answers, and a 'sad trumpet' (wa-waa-waaa-waaaa) sound for incorrect answers.
If the tone is more 'abstract', then a correct sound should have its pitch "going up" (like the Super Mario Coin sound), while an incorrect sound should have its pitch "going down".
You can also go "the Street fighter way" and have the program say the equivalent of "You Win!" and "You Loose!" in plain English.
Profesor Layton's series, for example, have their main characters tell you "That answer is spot on!" or "Mmm... that doesn't look too right..." (they still have trumpets and whatnot on the background)
Another important thing is duration: sounds derived from clicking a button should be short, specially if the user is supposed to answer lots of questions quickly. Sounds emitted after resolving a 5-minutes problem can be a little longer.
Not that I have a direct answer for you, but you might browse Freesound.org for good sounds. You can tag search for "success" and "failure" (or other suggested keyword around here like "crisp") to find sounds people have associated with those. Listening to a lot of samples should give you a better feel for what you want.
Absence of sound also counts. Rather than having a negatively-toned failure sound you could play no sound if the answer is wrong, and in doing so come off as less harsh on the user who may be struggling with the subject matter.
Reward them with a pleasant noise (not too loud or sharp) and give them empty air when they miss something. Antagonizing a math test taker is not likely to help them improve much. (in my opinion)
Another good place for examples of positive / negative user feedback sounds can be found by auditioning the system sound sets in a typical Windows installation. There are some great examples of the sonic motion alluded to by other answers in this thread. (just don't use them for anything other than reference of course.)
-j