Discuss drumming technique here
By djembeweaver
#27537
So, Michi, it seems you've finally tracked down the elusive tonpalo slap! Not quite as ground breaking as the Higgs Boson but very interesting nevertheless.

Thanks also for the very detailed analysis (far more thorough than mine). You can still clearly see that triple peak, which I think is characteristic of a really great slap. Also the M2 partial (I'm still not down with vibrational modes) appears to be crucial in determining the quality of the slap.

Jurgen: Don't worry - although my M3 is generally higher when I sit down and play simple things whilst focusing on technique, when I play more complicated stuff or try to play faster (or just on a bad day) my M2 is higher. On those MP3s I posted my M2 is generally higher than my M3 even in the echauffement :x

Anyway, to go back to one of my original points when I started this thread, you can actually hear these different partials if you really listen. I can sing my fundamental, then sing the next partial, and the one above that. If I really focus I can start to tease out one partial or the other by singing it as I play. I think this might be a really important practice tool.

Remember I started off this thread by saying that normally I hear an interval of a 6th between my tone and my slap, but that when I play well I can hear the octave? Well in that first spectrum I posted my fundamental was 350 Hz, which is an F, and my M2 partial was 589 Hz, which is almost exactly a D. That's an interval of exactly a 6th!

Moreover according to Albert Prak the theoretical ratio of M2 to M1 in a perfect circular membrane is 1.59. So 350 x 159 = 556.5. That's about a D flat which is a minor 6th. Pretty close to what I actually measured.

I measured my M3 as 740 Hz (an F sharp so almost exactly an octave). The theoretically perfect value would have been 749 Hz! That's astonishingly close.

So I think there is lot to be gained by paying careful attention to the separate partials in your slaps.

Lastly, Michi (and I'm sorry to drag this up again but I just want to know truth here), I just read an article called 'The Well Tempered Timpani' by Richard K. Jones where he states:

"Vibrating circular membranes do not vibrate with a harmonic series yet they do have an overtone series; this series not harmonic"

That's exactly what I was saying earlier when I noted that 1.25, 2.14 etc were not integer ratios.

Is Richard K. Jones wrong too?

Jon
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By djembefeeling
#27541
djembeweaver wrote:you can actually hear these different partials if you really listen. I can sing my fundamental, then sing the next partial, and the one above that. If I really focus I can start to tease out one partial or the other by singing it as I play. I think this might be a really important practice tool.
wow, I've just got the feeling that this might help me to improve my slaps a lot, because when I practice and focus just on the general sound of my slaps, I start to become deaf to differences pretty quick and my sounds become fluffed, as I could hear in my recordings. to have a specific point of perspective while listening and practicing would most certainly help. thanks again!

jürgen
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By michi
#27546
djembeweaver wrote:So, Michi, it seems you've finally tracked down the elusive tonpalo slap!
Yeah, almost as good as spotting a sasquatch ;)
Not quite as ground breaking as the Higgs Boson but very interesting nevertheless.
Dang! There goes that Nobel prize :)
You can still clearly see that triple peak, which I think is characteristic of a really great slap. Also the M2 partial (I'm still not down with vibrational modes) appears to be crucial in determining the quality of the slap.
Yes. One thing about Mamady's slap is that he really pulls out those higher-order harmonics, while very effectively suppressing the tone fundamental.
Anyway, to go back to one of my original points when I started this thread, you can actually hear these different partials if you really listen. I can sing my fundamental, then sing the next partial, and the one above that. If I really focus I can start to tease out one partial or the other by singing it as I play. I think this might be a really important practice tool.
I think it is. I've been trying a lot to be able to control the pitch of my slaps. You can vary the overtone spectrum with some practice and make them sound different. (I'm not talking about the tonpalo here.) There is a "higher" slap and a "lower" slap. The higher one seems to bring out something that sounds like an octave to me.
Remember I started off this thread by saying that normally I hear an interval of a 6th between my tone and my slap, but that when I play well I can hear the octave? Well in that first spectrum I posted my fundamental was 350 Hz, which is an F, and my M2 partial was 589 Hz, which is almost exactly a D. That's an interval of exactly a 6th!
Sounds like you were dead-right! :)

Moreover according to Albert Prak the theoretical ratio of M2 to M1 in a perfect circular membrane is 1.59. So 350 x 159 = 556.5. That's about a D flat which is a minor 6th. Pretty close to what I actually measured.
Lastly, Michi (and I'm sorry to drag this up again but I just want to know truth here), I just read an article called 'The Well Tempered Timpani' by Richard K. Jones where he states:

"Vibrating circular membranes do not vibrate with a harmonic series yet they do have an overtone series; this series not harmonic"

That's exactly what I was saying earlier when I noted that 1.25, 2.14 etc were not integer ratios.

Is Richard K. Jones wrong too?
[/quote]
No, Michi Henning was wrong :)

The harmonic series that applies to a string has integer ratios, but the harmonic series for a circular membrane doesn't. I didn't realise this at the time. Now I know better. I found a bunch of articles on the physics of circular membranes. Here are two links:

http://hyperphysics.phy-astr.gsu.edu/hb ... irmem.html

http://www.acs.psu.edu/drussell/Demos/M ... ircle.html

The first of these links includes a calculator that allows you to work out the (0,1) frequency based on tension, density, and diameter. From that, it should be possible to work out how much tension actually is on a djembe skin. I've often wondered about that. I don't think you can just take the tension you apply when tuning on each vertical and add it all up. You'd get several hundred kilograms of tension that way, which seems way to much.

Another fun project to tinker with at some point :)

Michi.
By djembeweaver
#27550
No, Michi Henning was wrong
Can I quote you on that? :giggle:
The first of these links includes a calculator that allows you to work out the (0,1) frequency based on tension, density, and diameter. From that, it should be possible to work out how much tension actually is on a djembe skin
As long as you know the density...how do you work that out?

Jon
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By michi
#27551
djembeweaver wrote:
No, Michi Henning was wrong
Can I quote you on that? :giggle:
Yep! Happens all the time, unfortunately ;)
As long as you know the density...how do you work that out?
Probably not too hard: cut a skin round of the correct size, put it on scales, and measure the thickness of the skin with calipers. Bingo, there's your density (after throwing in a slice or two of pie π) :)

Michi.
By djembeweaver
#27606
djembefeeling wrote:did some recordings and analysed my slaps with audacity. but when i try to export the graph, I can do so as a text only. how did you change it into a jpeg?
Taking a screen dump is easy when you know how. On Windows XP I just selected the spectrum window, held 'Alt' and pushed 'Prt Scr'. That copies the contents of the window to the clipboard. Next I just pasted it into Powerpoint and saved the slide as a jpeg. Easy.

You'll have an equivalent with a different operating system but it shouldn't be difficult.

Jon
By djembeweaver
#27728
djembeweaver wrote: Remember I started off this thread by saying that normally I hear an interval of a 6th between my tone and my slap
Er...no I didn't. I've just gone back and re-read my original comments. It's amazing what you can convince yourself you've said.

Actually I said I heard an interval of a fourth. So I've been mucking about this morning and this is what I've discovered:

When I sing my tone and first-slap-partial I consistently hear an interval of a fourth. This is odd, seeing as the spectrum analysis tells me it should be a sixth.

Next I found the note I was singing on a piano, and compared that to the frequency of my tone fundamental from the spectrum analysis. Here's where the discrepency lies: I was singing a major third of the fundamental frequency. The interval between a major third and a sixth is a fourth, so that's why I was hearing a fourth interval! (needless to say the slap partial I was singing was bang on). Funnily enough I still couldn't hear the note audacity gave even when I played it on the piano and played a tone.

So that begs the question of why I was singing a major third of the fundamental and why couldn't I hear the fundamental as given by audacity...

Well, you might say there's something wrong with my pitch....unlikely: I studied classical trumpet from the age of 8 and have my grade 6 classical theory. I know all my intervals and can sing them. While I do not possess perfect pitch (very few people do) I possess good relative pitch. I can sing in harmony etc too so my pitching is OK. Play me any note and I'll sing it back to you along with any interval you care to name.

The second possibility is that there is a major third partial hidden in there somewhere. Indeed when I looked at a spectrum of a tone again and cranked up the resolution to maximum, a small peak appeared at the major third. It was very quiet though...I even downloaded a sine wave generator and yup - I can hear a major third in a sine wave of 392 Hz (so surely this can't be a pure sine wave...Michi what do you think?)

One observation that may be relevant is that the bandwidth of the peaks gets progressively smaller as the frequency increases. Does that mean that the note becomes more 'pure' at higher frequencies? If this is the case then a tone actually contains a range of frequencies and Audacity takes the mean. Alternatively this could be an artifact of the analysis. Indeed audacity gives slightly different values for M1 across successive tones (ditto the other partials).

Anyway, one last thing I did was get 2 other people to try to sing the note of the tone. They both found it really difficult (even though they are both good musicians) and each sang a different note.

Conclusion? Confused!
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By djembefeeling
#27729
djembeweaver wrote:Conclusion? Confused!
Interesting -- there seems to be more to good sounds than spectrum analysis can tell. I am relieved :D But seriously, I wondered by listening to my sounds to pick the good ones for spectrum analysis that I couldn't tell which ones have the M3 and higher partials I was looking for. Some of the high M2 ones did sound much better...
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By michi
#27754
djembeweaver wrote:Next I found the note I was singing on a piano, and compared that to the frequency of my tone fundamental from the spectrum analysis. Here's where the discrepency lies: I was singing a major third of the fundamental frequency.
It's interesting to hear you say that because the same thing happens to me occasionally too. I often sing the fundamental, particularly when comparing pitches of different drums or trying to tune a drum to a target pitch. Every now and then, I find myself in the exact same quandary. I sing a note, stop, try again because I realize "no that's not the fundamental but a harmonic", and find myself singing the fundamental exactly a major third below the first attempt.
So that begs the question of why I was singing a major third of the fundamental and why couldn't I hear the fundamental as given by audacity...
I have no idea. Maybe it has something to do with hearing a harmonic an octave above the fundamental and then transposing that down? I'm just guessing here.
I know all my intervals and can sing them.
Same here. I'm pretty sure that there is nothing wrong with your understanding or perception of pitch. This is bound to be some psycho-acoustic phenomenon, where harmonics suggest a fundamental that is a major third above the true fundamental. It's not the step up from (0,1) to (1,1) because that's a factor of 1.59, which is too much; a major third is 1.26. (1.59 is an augmented fifth.)
The second possibility is that there is a major third partial hidden in there somewhere. Indeed when I looked at a spectrum of a tone again and cranked up the resolution to maximum, a small peak appeared at the major third. It was very quiet though...I even downloaded a sine wave generator and yup - I can hear a major third in a sine wave of 392 Hz (so surely this can't be a pure sine wave...Michi what do you think?)
I honestly don't know. Possibly, there are beat effects too. If you play frequencies f1 and f2 simultaneously, there are beat effects that generate f1 - f2 as real audible sound. It's possible that the major third we are hearing has something to do with this.
One observation that may be relevant is that the bandwidth of the peaks gets progressively smaller as the frequency increases. Does that mean that the note becomes more 'pure' at higher frequencies?
No. A Fourier transform decomposes a sound into its fundamental frequencies. There actually is no other sound contained in the signal other than what a Fourier transform reveals. If you take all the harmonics shown in a Fourier transform and mix them together in the correct proportion of loudness, you re-create the original sound.

The frequency intervals get narrower as we go up the series simply because that's how the series works. (The logarithmic scale of the diagram visually exaggerates this effect. On a linear scale, the steps are much wider.)
If this is the case then a tone actually contains a range of frequencies and Audacity takes the mean. Alternatively this could be an artifact of the analysis. Indeed audacity gives slightly different values for M1 across successive tones (ditto the other partials).
A tone does contain a range of frequencies. Assuming an ideal and perfect membrane, the only frequencies you should find are those in the series. However, because a goat skin is far from perfect, and a drum is far from circular, and because the shell and the skin are coupled resonators, the mathematical model can describe reality only so far. There are other frequencies present (even though the harmonics in the series dominate).

Moreover, the sampling has its own source of error, both in the time and the frequency domain. The values reported by Audacity depend on the sampling rate of the source. For CD source material at 44.1 kHz sampling rate, if you ask Audacity to use 1024 samples, you get 512 frequency bins. Each bin has a center frequency, but with an error band of 43 Hz. The actual value of the harmonic may be up to 21.5 Hz lower or higher. Double the samples, and you get twice as many frequency bins, with a frequency error of 21.5 Hz (10.075 Hz up or down). But now, the error in the time domain doubles. An FFT is only as good as its input data. It can't infer information that wasn't there in the first place.
Anyway, one last thing I did was get 2 other people to try to sing the note of the tone. They both found it really difficult (even though they are both good musicians) and each sang a different note.

Conclusion? Confused!
Difficult to know. Even a different position in the room of the respective listeners can have a major effect, due to standing waves.

My co-teacher has a very large living room with gabled roof, probably around 6 m (18 ft) high at the tallest point. We recently were practicing with the dunduns on their side. For a few rhythms that need ballet style, we put the sangban upright. The pitch of the sangban was noticeably different when upright, about a semitone lower. We actually put the drum on its side and back upright several times to compare. We both agreed that there was about a semitone difference.

What's happening here is that the sound of the drum reflects off different parts of the room in the respective positions, which can lead to certain frequencies being amplified by resonance more than others. The drum doesn't project all frequencies with the same intensity in all directions, so the pitch (or, rather, the received harmonics) change as the position of the drum changes…

Cheers,

Michi.
By saultrain
#30510
I have to say, this topic is fascinating. In another thread I posted this video of master drummer M'Bemba Bangoura:

I like this clip because the audio and video were recorded with such great quality. To my ears, the tone vs. slap interval sounds like a fourth. In fact, to me, bass to tone sounds like a fifth and then tone to slap sounds like a fourth which together makes a harmonious fifth chord. Does it sound that way to others? Am I mistaken?
By djembeweaver
#30523
To my ears, the tone vs. slap interval sounds like a fourth. In fact, to me, bass to tone sounds like a fifth and then tone to slap sounds like a fourth which together makes a harmonious fifth chord. Does it sound that way to others? Am I mistaken?
Tone to slap sounds mostly an octave to me (what it should be for a really good slap), though as we've already discovered the slap is a combination of several partials (there are 3 of them bunched around the octave and a lower one at around a fifth that is normally suppressed).

It's hard to hear the relationship of the bass to the tone since they are so far apart. With a drum tuned like this the bass will be around 80 Hz (or thereabouts) and the tone will be around 400 Hz.

Jon
By saultrain
#30561
After listening again, I'm not sure why I initially heard a fourth (I was using a guitar to try to identify what I was thinking I was hearing). Now I hear mostly a fifth from tone to slap, but I can also sort of hear an octave in there too. Like you mentioned it's not a pure pitch obviously. I'm new to drumming so tuning and pitch as it relates to drums is a new way of thinking and listening. Hard to tell exactly what I'm hearing vs what I'm imagining I'm hearing.

Alright then--guess I'll just keep practicing.

Peace.
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By michi
#30570
You can pick pretty much any interval you like, especially when the slaps are played on a djembe with nice crisp skin that produces plenty of overtones. Depending on what harmonic you perception latches onto, you hear different intervals.

Check out the Wikipedia djembe page. It has diagrams of the different vibrational modes.

Michi.