Re: Harmonics of tones and slaps
Posted: Tue Jul 03, 2012 7:39 pm
I took the images with a screen capture program.
Djembe Community and learning resource.
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!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.
Yeah, almost as good as spotting a sasquatchdjembeweaver wrote:So, Michi, it seems you've finally tracked down the elusive tonpalo slap!
Dang! There goes that Nobel prizeNot quite as ground breaking as the Higgs Boson but very interesting nevertheless.
Yes. One thing about Mamady's slap is that he really pulls out those higher-order harmonics, while very effectively suppressing the tone fundamental.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.
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.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.
Sounds like you were dead-right!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!
[/quote]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?
Can I quote you on that?No, Michi Henning was wrong
As long as you know the density...how do you work that out?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
Yep! Happens all the time, unfortunatelydjembeweaver wrote:Can I quote you on that?No, Michi Henning was wrong
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 ofAs long as you know the density...how do you work that out?
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.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?
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.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
Interesting -- there seems to be more to good sounds than spectrum analysis can tell. I am relieved 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...djembeweaver wrote:Conclusion? Confused!
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.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.
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.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...
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.)I know all my intervals and can sing them.
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.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?)
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.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?
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).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).
Difficult to know. Even a different position in the room of the respective listeners can have a major effect, due to standing waves.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.
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).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?