Wow, it's even right now! The differences in what we perceive fascinates me. I chose file 1, but I'm interested to know which file had both notes the same, if any at all.

I'll get my girl to try this later. I'll be curious what her pitch perfectness makes of it. Me personally? I can't hold a tune in a bucket. Though I still try

@GrannyCheeseWheel The ears playing tricks on us and stuff!
Yeah, would love to try more of these. There's a great series on YouTube on psycho-acoustics if you're interested. I'll try and hunt down a link.

Nice to see this is getting attention! I'll keep the pole open and the files up indefinitely so this can continue.

The results are pretty much trending the way I and probably most researchers would anticipate. However I'll confess that they're a bit more evenly distributed than I thought they would be. That's good, it means both camps have fair representation.

One interesting thing I forgot to include in my initial post is that perfect pitch or absolute pitch offers you no advantage. All it does is let you precisely identify which notes you hear, which is not required for this test. In fact, I'd argue that having perfect pitch just cements your immediate perceptions even more, making it especially hard to get out of that and justify how the alternative could make any sense. That is exactly what happened to me and my friend.

@Mayana
Extremely interesting find. That suggests to me one of two things: either you aren't so good at picking up differences in octaves at least in that bass range, or the timpani sound is straddling a threshold in your brain for lack of a better word. I'll lean toward the latter because you say you waver depending on which part of the sound you listen to. I've experienced that myself, but not on this. If I was doing actual research, your find would probably make me consider adding an addendum to the paper

@GrannyCheeseWheel
Haha classic reaction. How could there be any debate indeed!
And don't worry, this is not a dirty trick which relies on bias or messing with your head.

@Aaron
You've done what I hoped you wouldn't and overthought it . No worries though, you're actually onto something!
The objective of this test has nothing to do with midi, it is fully based on your perception of the sounds. However, the midi theory has merit and brings us to how the timpani is notated. Midi seems to mirror the notation so far as I know, that's why if you play a mmiddle c while scrolling through sounds on a keyboard, some sounds will appear to jump to a different octave.

For example, if you're playing a synthesizer which follows the midi spec correctly, organs will often appear to be an octave lower than most other sounds. This is because the largest pipes and or the lowest drawbars in an organ are tuned to sound an octave lower than written. However the timpani is not such a clear-cut case; depending on how you heard this test, you may or may not hear an octave drop when switching to the timpani. In any case, midi does seem to be accurate to timpani notation, so whether sheet music or synthesizers are your reference, you're getting the same data.

I've purposefully been avoiding going into the nitty gritty because it's fun reading how people speculate. When do you guys think I should reveal all?

Why don't you reveal it all now? The suspense is killing me! You could just add a heading to the bottom of the original post and advise people not to read it until they completed the experiment.

I'm with 3 on this one.  they sounded great for the  first hundred ms of each but then I felt like the little drum thing wavered just a bit and that made me question myself too much until I went with can't tell.

Interesting.

Spoilers
here

So, the range of a typical set of four timpani is written realistically between about second octave D and third octave g. Below that the overtones just make it too wet, and above that it just sounds dead. You can, of course have larger sets of timpani to create larger ranges, but a set of four is pretty standard.
The timpani strike is in the sweet spot of the third drum from the bottom which is typically tuned comfortably from a-flat two to e-flat three, which means it is the second file. since the first file is playing on octave two, and the second is playing on octave three.

Do not read if you haven't voted!
spoiler alert!
Ok, so I also agree with many people here,, to be honest to me none of them exactly matches it but if I had to pick one I'd choose 2 since it was closer. I don't have a perfect pitch, but I play piano and guitar, and I also sing, so I'd say I have a quite good relative pitch.
It's not about the base, of course the timpani would always beat the piano's base, but concentrate on the end of the sound, the sound when the note almost fading out, that's how you usually can tell if a guitar is slightly out tuned as well.

Okay, all will be revealed in this post. If you intend to take the test without any bias, skip this post please, and probably don't read the rest of this thread for that matter, until you're done the test. The pole and files will remain up indefinitely so that newcomers can still participate if they choose.

My basic idea with this test was to see how strongly people were affected by the missing fundamental concept. The wikipedia article linked to above gives a pretty nice explanation of the idea. If that article is complete gibberish to you but you are still curious about what is actually going on, this audio file I recorded will explain everything and show examples. The file is almost 22 minutes in length and goes through the test, as well as why different people may perceive different things when they hear the files.

If you heard file 1 as being the same notes, you've fallen for the missing fundamental illusion. Don't worry, I fell for it too. all it means is that your brain is doing something which is well-documented: it is perceiving a fundamental frequency which isn't actually there. For the rest of this post, I'm going to refer to you as a fundamental hearer, since your brain more easily fills in missing fundamental frequencies.

If you voted for file 2, you technically heard the sounds as they were notated, as drums61999 pointed out. If you were going purely by the notation, file 2's notes were exactly the same. For the rest of this post, I'll be referring to you file 2 voters as overtone hearers, since you have a slightly better ability to hear individual overtones and not be so easily fooled by a missing fundamental. But don't be too smug. Just because you saw through this one doesn't really mean much. At some point, everyone will perceive a missing fundamental in some way, we just have different thresholds for it. Hopefully the audio I linked to above will show that clearly.

Some people here said they couldn't tell which to vote for because the two instruments sounded out of tune. There are a number of explanations as to why this could be. Timpanis and pianos both have a bit of a weird harmonic series which can make things sound a bit out of tune. It's actually pretty wild that certain instruments fit together as well as they do, because their harmonics are far from perfectly in tune with each other. When listening intently to the files in this test, I can totally see how some people could perceive that the files aren't perfectly in tune. Perhaps the tuning could've been improved on my part, I haven't actually tried.

Perhaps a more fair test would have been to generate two very different test files with a synthesizer. That would eliminate prior knowledge of the instruments and their notation/midi counterparts as an influence, and would also avoid tuning problems. I didn't want to take that approach, though, since setting up such deliberate tests means that someone subjectively has to decide what the choices should be. Me, being a fundamental hearer, would probably set up such a test in a different way from an overtone hearer.

So at the end of the day, what does it matter? To be honest, I don't have an idea, but I do have weird speculations. First off though, I do not believe that the way you heard this test or any other similar test will dictate much in your day-to-day life, even if you're a super geeky audio professional. The music and sounds we usually hear are normally not so wildly different when it comes to perception. People will naturally notice different things in certain sounds, but few cases will be this drastic. Even when perceptions do differ, it doesn't really affect the enjoyment of the music. If it does, there's probably a bigger issue needing addressed.

But the phenomenon does rear its head sometimes. If you have perfect pitch, it can make things, uh, interesting from time to time. And if you frequently engage in critical listening, it might be useful to know how you naturally hear things to inform your focus. For example, me being a fundamental hearer means I am less sensitive to what goes on in the mid and high frequencies of a sound. For instance, I really enjoy sounds with certain harmonics which stand out. Even if the fundamental is comparatively soft, I tend to hear it pretty clearly anyway. Unless I have a reason to work out the harmonics, I will hear them as the extention of a fundamental, so effectively I'm turning distinct harmonics into a sort of unique seasoning. I can only speculate, but I hypothesize that an overtone hearer might find it harder to choose which way to hear certain sounds. As a result, they may be more careful and picky about the instrument tones they like, especially in certain cases.

On the opposite line, I absolutely hate making subtle frequency corrections. I focus so much on the bass tones, that listening for peaks and dips in the harmonics feels unnatural, like I have to break through the wall of fundamental to get at the delicate stuff underneath. Of course this is a skill that can be worked on, and my hearing is fine so there's no issue there. An overtone hearer, might possibly find it a bit easier to spot exactly where a sound has gone wrong, or where two microphones have a phasing issue, or anything really that involves a subtle tonal change.

One last idea which is admittedly very far-fetched also crosses my mind. Perhaps those who more easily hear fundamentals tend to gravitate toward their intuition, at going with the flow, where as overtone hearers are better at being critical and deliberate, to really piece things apart to find out how they work. That just hit me as I was writing this post, and it sounds too postmodern for me to be comfortable with it (nothing against alternative views, I just have my limits as to how far I'm willing to go). But hey, those ideas sounded good when they first came to me! Of course, even if these were actual trends, there would be a lot of external factors involved, so I doubt anyone could ever make too much out of it.

Few, I think that's enough from me for now. Hoped this has been fun! I'll of course be checking back to see if this carries on.

That was very interesting. When I voted for file 1, I thought: "Nobody will pick differently. It's so damn obvious." But what do I know? The results at this moment are 40, 40, 20.

@19, interesting, I'll have to listen to that and see what I notice! I haven't heard it yet as of right now.

@20, the results are almost evenly split as you said. Since more and more people are having trouble telling, I'm starting to think that the clips aren't all that good at revealing anything haha

Ahh, harmonic series. When taking brass techniques in college we had to know up to the sixteenth partial.  I've forgotten most of it. It's neat though.