Is the "Earth Harp" real (acoustically)?

AlephZero

That's consistent with problems in the design of pianos caused by unwanted longitudinal vibrations of the bass strings "coloring" the sound of higher pitched notes. Middle C is about 262 Hz. The equivalent for a 8-foot-long wire would be 262 x 42/8 = about 1375 Hz, which is in the right ballpark for the problem frequencies with pianos. The speed of sound in most engineering metals is similar, so the different matierals aren't very significant.

zoobyshoe

Good find, Evo. The thing makes more and more sense.

Evo

So this "Close" guy claims to have invented it eh? Seems it's been around for quite awhile.

zoobyshoe

The claim is he invented the first one in 1999:

http://earthharp.wordpress.com/about/

Evo

Excellent find, explains even more.

Jiminy

From his website:

"The Earth Harp uses architecture and landscape as part of the instrument. The architecture becomes the instrument."

and

"It turned the valley into a giant harp!"

___________________________________

That is such a load of fertilizer.

jreelawg

That is a bit of an exaggeration, but I think people know what he means. I think it's cool. If someone refuses to believe it's an actual instrument when it is, it's got to be awesome right!

Jiminy

According to responses I've seen to the video on YouTube, a number of people are buying into the marketing speak. People claiming the theater is actually like the sounding body of a guitar, stuff like that. You could claim that for ANY instrument that plays inside a reverberant hall, though it would be silly.

The jury is still out on whether it's real. So far no one here has presented anything that overcomes the long list of red flags I previously laid out.

And 1000 foot strings? Please. You're not going to rub a 1000 foot string and get any sort of instant response like the tones that are coming out of his "sound box".

The only reason to believe it's real at this point is faith and hope.

I've got some inquiries out to credentialed acousticians right now and will be interested to hear what they say. Would be illuminating to know why neither I nor any musicians I know can't come close to simulating anything like this with regular sized string instruments, despite trying various techniques. We've even used rosin, but maybe you need magic, New Age rosin made from ground up unicorn horns.

zoobyshoe

Eh? This ignores everything that has changed now about your assumptions.

Everything you assume about string vibration, tension, length, etc. becomes moot when the strings are treated as thin rods instead. Rods can, in fact, be vibrated in the way he claims for his strings. You'll have to start from scratch with new formulas about longitudinal waves in thin rods.

Given the very high pitch of the aluminum rod in the video you ought to consider the tone produced by rubbing a common violin string this way might be ultrasonic.

Jiminy

Hi Zoobyshoe,

I haven't really made any assumptions about anything. I'm applying real-world acoustical principles, and I know for a fact that in the physical world, mass, resistance, amplitude envelope and frequency are inextricably linked, no matter what sort of wave you're talking about.

Moreover, I've already noted the problems with the theory that these strings are behaving as rods and so far these objections have not been addressed by anyone. I'll expound a little bit on a few of those points:

1) In each of the rod videos that were posted (which were fun to watch in and of themselves), the mounting of the rod was clearly at one point, a 2:1 nodal point, the middle. The rod's own rigidity allows this, and the l-waves thus produced are at their greatest amplitude at the rod ends. Problem is, the Earth Harp does not use rods (with their own rigidity, allowing for free-end vibration), rather, it uses "strings" (heavy gauge wires) which must be mounted at each end. This doesn't allow for any sort well-mannered periodic l-wave; It's a transverse wave environment.

2) In the rod videos, the swiping is done swiftly over nearly half the length of the rod and always from the nodal end outward, whereas with the Earth Harp, the swipe is very slow and even and the ratio of swipe to the length of the strings is very small, plus which you can never go from the 2:1 nodal mount point outward to a free end since there is no free end.

3) The decay time in one of the rod videos is about 12 seconds, and would've been even longer without the styrofoam cup being placed on the end a few times. Whereas, with the Earth Harp, the decay time is about one second. Instruments with decay times longer than about 1 second (timpani, chimes, cymbals, tam-tam, etc.) need to be dampened at certain points by the performer if the onset of a subsequent note would lack clarity (for being covered by a still-resonating instrument). But you'll notice that this does not happen with the Earth Harp, what with it's manageable decay time. At no point does the performer ever have to dampen. Chimes have similar decay times to the rods in the videos. You can't even really play moderately paced figures on the chimes without the notes getting lost in the wash, and with the timpani or glockenspiel (both having similar decay times of a few seconds), un-dampened quick-ish notes increasingly lose their clarity. Not so with the Earth Harp, with its decay time less than 10% that of the rods.

4) Speed of onset is another issue. The rod videos show a gentler full onset, whereas the Earth Harp has a quicker and more immediate onset. A 1000 foot long wire having a much quicker onset envelope than a 5 foot rigid bar cannot be reconciled to the principles of real world instrument acoustics.


5) In each of the rod videos, the harmonic content is very simple and not very rich and does not in any way translate to the much thicker, more active, and decidedly nasal and buzzy harmonic content produced by the Earth Harp.

______________________________

And while an attempt was made to address a few of the red flags I listed in my original post, I already highlighted those errors as well. The physics of vibrating bodies are a very particular thing, and the particulars matter a great deal. Like I say, I've done a fair amount of formal study regarding general acoustics and especially instrument acoustics. As an experienced composer, I'm regularly evaluating sound by ear and with my spectrum analyzers, and I edit and process generated and sampled sound waves at the sample level. I perform all sorts of experiments on established instruments as well as "found percussion" (steel mixing bowls, steel dog food bowls, clay flower pots, different types of tone wood, conduit tubes, ceramic floor tile, etc.), plus which, I regularly scour the scholarly books on instrument acoustics which I own, so I can guarantee that none of what I say here is based on "assumptions".

Nevertheless, I am intellectually curious, so like I previously mentioned, I've sent out a few inquiries to some credentialed experts whose areas of specialty make this subject right up their alley. I'll report back here as soon as I get any replies.

Regardless, I'm not too fond of the New Age marketing speak whereby a valley "becomes the instrument".

Thanks for taking the time and interest.

-J

zoobyshoe

To hoax the thing, then, he'd have recordings of each note that were activated by pulling on the strings. The mikes he seems to be using as pickups would actually not be in operation. They would function as a front to explain the need for a loudspeaker system.

Is something like this what you're thinking?

jreelawg

Your first post was an attempt to debunk the idea that this instrument utilizes transverse vibration of the strings to make it's sound. Almost all of your red flags from that post are completely invalid because the claim is that the instrument utilizes longitudinal vibrations of the strings.

Notice in the video of the rod, that in the second swipe, the sound picks up, and is loud immediately as he starts swiping. The guy in the video does swipe all the way down the length, but it's not in any way necessary to do so to get the longitudinal effect he gets.

Notice also that he's making sound from the moment he starts (while his hands are still swiping)

Jiminy

Zoobyshoe,

To be honest, I don't even want to contemplate it being a hoax. I would much prefer it were real. Maybe one of these acousticians will get back to me with something, some phenomenon I haven't taken into account, but so far I can't reconcile it. Plus which, it'll be much more interesting if it is real. Until I have it confirmed one way or the other I'm suspending my partial disbelief for the time being, because if I err, I want to err in favor of giving the guy the benefit of the doubt for now.

Theoretically speaking, if one were to fake this, the notes themselves would probably be generated via a physical modeling module rather than a sampling module. If it were samples, each one would have to be looped and you'd have to program seamless release triggers. All that would be much easier with physical modeling. Depending on how much off-the-shelf stuff vs. custom kit were used, you could potentially end up with something about the size of an iPhone, not including the triggering rig.

As far as triggering the notes is concerned, you'd need some sort of custom rig that responds either to the pressure applied to the string, or perhaps merely to touch, via the interruption of some sort of very low level electrical charge. He's got those things mounted on the each string roughly about 10 feet from his playing position, so those could be a terminal of sorts I suppose, but mechanical and electrical engineering are not areas I know anything about, so I could be talking out of my you-know-what as far as all that is concerned.

The most charitable scenario I've been able to come up with so far is that there is some part of this which is acoustically valid, and the aspect of the extra long strings, be they 50 feet or 1000, are just a part of the stagecraft, so to speak. And like I say, part of my problem is understanding why such a monumental disparity of string length per installation would result with notes of identical tuning.

I'll report back here when I find out something more concrete. I hope it's good news.

Enjoy your weekend everybody.

Jiminy

Was it? How so? At what point in my first post did I posit that each and every of the 10 acoustical red flags I listed was based on transverse wave assumptions? And they certainly don't imply that themselves. Number 5 mentioned perpendicular/transverse excitation, so that makes 1 out of 10 being invalidated only if this turns out to be legitimate. For now, all you're basically saying is that "You're wrong because you're wrong", without really getting into the nitty gritty of the specifics. I am perfectly fine with being wrong about an interesting subject like this, I just want to know why.

My initial post was to list a number of acoustically-based red flags. Longitudinal vibration of a mass is not conjured from the teardrops of magical harp fairies, and that being the case, they are still subject to certain acoustical principles which somehow do not accommodate mere assertion or wishful thinking.

And as for saying that this is a longitudinal mechanism simply because someone has asserted same, well, again, that remains to be seen. If that is the case, it may very well be the first time in the history of music that someone has rubbed a wire parallel to its length and produced a musical, periodic wave form, high in active harmonic content, with an attack envelope and decay time that are both conveniently just right for common musical purposes.

Fact: It takes the guy with the 6 foot rod about half a second to make an initial full onset.

Fact: In musical terms, that's a long time.

Fact: The Earth Harp, with it's considerable length and increased mass (which, again I say, unlike the rod does not have a free end to vibrate since it must necessarily be mounted at both ends), has a very quick onset that is perfectly able to play the fast section at 1:37. Those are eighth notes at a tempo of about 108 bpm, meaning the notes themselves are about .27 or .28 of a second at the slowest. The singing rod has way too slow a response for this, and like I noted previously, the decay times are not even in adjacent ballparks.

zoobyshoe

Jiminy, here's another rod video showing an effect I find paradoxical:



At about 1:45 he is holding the rod at the midpoint and getting a certain pitch.

Then he changes the point at which he's holding the rod, strokes the longer side, but gets a higher pitch.

The pitch the rod produces, it seems, is determined by the shortest of the two lengths, and that monopoly holds independent of which length you rub.

Maybe this is not mysterious to you, but it strikes me as counter to the more length = deeper pitch you'd (I'd) expect.

jreelawg

The singing rod only demonstrates the possible feasibility of something like what he created. It's really a very different thing though. It's hard to compare the two.

The strings being mounted on both ends must dampen the strings so that they don't ring out like the singing rod. Instead of the transverse wave reacting directly with the air, they must instead transfer energy to the vibrating body.

The singing rod is vibrated from the moment that the friction begins, it's just that it takes a certain amount of force applied to it to get it to vibrate a lot. While the sound initially is quiet, if he were to somehow apply more friction faster, it would be louder quicker.

Because the earth harp may be dampened the way I suggested, it may not be able to ring out and build up with every additional stroke. And the instrument is amplified.

It would be interesting to know how loud the earth harp is un-amplified.

Just a few thoughts.

zoobyshoe

I'm searching for a video where someone tries clamping the rod at one or both ends. Haven't come up with any.


This video, though, shows what happened when the demonstrator experimented with bending a rod simply to make it easier to cart around from one demonstration to the next.



My guess is that the result has something to do with the fact he has "work hardened" the aluminum at the bend. This might be equivalent to clamping the rod in a vise, say, at one end, though I'm just speculating.