What causes wolf tones? (Full Version)

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a_arnold -> What causes wolf tones? (Apr. 5 2007 15:37:25)

I've hear reference to wolf tones here.

Is that when a fretted string vibrates against another (unintended) fret? If so, does it refer to the string touching the fret between the nut and the fretted point, or between the fretted point and the bridge?

Tony Arnold



Ricardo -> RE: What causes wolf tones? (Apr. 6 2007 16:34:39)

I think, according to Ramirez book which covers this in detail, it is a bit of a mistery what causes wolf notes. As described, I have never noticed them on ANY guitar I have ever played, but I could be playing through them unknowingly. They are weaker notes than all the rest if played with equal force. Segovia complained about them getting worse on his Hauser, and had to cut some pieces out of his repertoire because the weak note ended up being one he wanted "brought out". I have notice in live settings with microphone when some notes are weak or too strong, but that is not the same as "wolf notes" I think.

Anyway, Ramirez talks about how this is weird but common problem in old violins and cellos etc, they tried to fix by vibrating the top with metal filings on the wood. The metal fillings would gather up in areas not vibrating strong enough. So the luthier would file that spot to thin the wood. The player would play the violin and the wolf note would disappear for a while. Then unexplainably the weak note comes back, even weaker than before. Essentially, fixing the instrument made it worse, or ruined. So Ramirez did not even try that to fix the problem Segovia had. Instead he studies spherical acoustics and designed a fin of wood, with the body shape cut out smaller inside the guitar, and this supposedly fixed the problem. His designed is patented so no other maker can use it. The instrument is called "De Camara" guitar, and has been around since 1985 I think.

Like I said, I never noticed these wolf notes so hard to say if I would notice the supposed improvement this guitar has.

Ricardo



nhills -> RE: What causes wolf tones? (Apr. 6 2007 18:54:00)

Wolf notes can also be notes that are unusually strong, rather than weak. They seem to occur when the natural resonant frequency of a top, brace, etc. coincides exactly with a note that is played. Some luthiers change the tap tones of the top so they are NOT on any note on the fingerboard at standard pitch. The same could be true for weak notes if it occurs on the pitch of a heavy brace. The problem referrs to single notes - not to a generally weak string or range of notes.

They're more of a problem with classical guitar than flamenco because classical relies more on subtle shades of dynamics of single notes.

I have heard them on some guitars - they can be quite startling!

Cheers,
Norman



a_arnold -> RE: What causes wolf tones? (Apr. 6 2007 22:42:31)

Thanks! I was really on the wrong track there. Does anyone have wolf tones on a flamenco, or do we just tend not to notice them? I have never noticed any on mine (I've had 6 at one time or another).
Tony



Ricardo -> RE: What causes wolf tones? (Apr. 8 2007 5:01:57)

quote:

Wolf notes can also be notes that are unusually strong, rather than weak. They seem to occur when the natural resonant frequency of a top, brace, etc. coincides exactly with a note that is played.


Well, I know what you mean there, and I did not think that was what was meant in Ramirez book. But you know, I have never played a guitar that did not tap at SOME frequency. And all the frequencies are possible on the strings as overtones, so I don't see how a luthier could avoid having some stronger notes. Majority of guitars i have played, especially miked up live, you notice this vibration and the exact frequency when you stick the mic right in the sound hole and tap the board. MOST guitars have a very strong note in the bass between G and Bb in my experience. Playing those notes on the guitar you can suddenly notice one of those notes is VERY strong in at least two octaves. For live sound, once you notch that frequency out, the ENTIRE sound of the guitar gets weaker, but more clear. From there you boost the level and you are good to go.

Ricardo



Per Hallgren -> RE: What causes wolf tones? (Apr. 8 2007 7:36:22)

Wolf tones have their names from the howling strong tone in cellos if a certain resonance is tuned wrong. As a guitarmaker I have no specific knowledge in cellos however so let us move on to guitars. Guitars also have wolf notes, as they unappropriate is called, and as you have said they can be notes that are stronger or weaker than the others. They are caused by too strong resonances, mostly in the top or the air of the box. If a resonance is very strong the energy from the string is used up in a shorter time thus causing a weak note. In theory it can be any resonance causing trouble but for the guitarmaker it is only in the frequencies below ca 700Hz that it is really possible to work with afterconstruction tuning. Luckily it is also those lower resonances that are the main problems. In higher frequencies the resonances are too close to each other and the antonodes are small and overlaying eachother making tuning impossible without changing too much of the rest of the resonances. Sometimes it is possible to change the tuning of a resonance moving it away from the frequency of the weak note on the fingerboard, sometimes it is possible to hold back the troubling resonance by damping it, making it less strong.

This is complicated and difficult to explain. Point out what you don't understand and I try to explain further.



a_arnold -> RE: What causes wolf tones? (Apr. 11 2007 2:24:31)

Wow, Per...
Tell us more! You can correct some wolf tones after the guitar is built? I had no idea this was possible. How? Is a common practice? Do you do thi after the finish is applied? I assume you shave wood from struts or soundboard. How do you know where to start?
Tony Arnold



Jim Opfer -> RE: What causes wolf tones? (Apr. 11 2007 12:17:18)

It's all explained here in great detail.

http://www.celticcollections.com/artists/wolftones/wolftones2.htm



Per Hallgren -> RE: What causes wolf tones? (Apr. 11 2007 14:18:40)

I have no idea if "after construction work" is common or not. I am selftaught as a luthier so my way to do it is mine and there are many paths to the mountain top. I would be surprised if I was alone though. Working mainly with classical guitars as I do, it is important to know the technique to adjust the response, wolf tones etc. Classical players are picky [;)]

The theory behind it is simple, the execution of it is difficult... It is a fact that the resonances of the soundboard and back follow a certain pattern in exactly the same way as the string harmonics do. Think of a string. Exciting the string by plucking it you get it to vibrate in its fundamental frequency (A is 110 Hz for example) but it also vibrates in harmonics simultanously where the string is divided in smaller parts, at the middle (12th fret) for the first harmonic, at 1/3 and 2/3 of its length for the second harmonic etc. A soundboard works in exactly the same way. Only difference is that the soundboard is two dimensional while the string is only one. When one knows how the resonance patterns look like and at which frequencies they appear on a certain guitar design it is also possible to know which area(s) of the top one can expect to work to change a wolf tone for example. The problem is that everything in a guitar is coupled so changing one resonance can create new problems.



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