|
Dave White wrote:
"Do some searches on "Wolf notes" (and before anyone has a go at me that this is only the correct term for bowed instruments, this is to help in the search)."
We could argue all day about what constitutes 'correct' usage. The mechanism that causes the 'wolf' note that is common on 'cellos is about the same as the one that causes the 'thuddy' low notes on many guitars. The difference in the outcome has much more to do with the way the strings are driven than anything else.
It's possible that what Mike has is still a 'wolf' note, even though it only showed up when he changed strings. If he swapped gauges it's likely that the way the string is driving the top differs, and that could make an inconspicuous problem into a big one. Again, 'cellists know that switch to a diferent string gauge is one way to tame a wolf, at least sometimes.
The wolf has far more to do with the pitches of various resonances of the guitar than anything else. Usually the 'main air' resonance is somewhere near G, and, if the top is strongly coupled to it, so that it can feed string energy into the air resonance fast, that note will be loud and lack sustain. Our ears are not very sensitive to changes in level: a doubling of sound _power_ (3 dB increase) is generally a just noticable change in _loudness_. We don't notice that the sound it twice as loud; only that it lasts half as long.
It's also common for the 'main top' tap tone to be close to an octave above the 'main air' resonance. In that case there can be two more things going on: the bridge is moving a lot, so that the end of the string is not fixed, and the energy of both the fundamental and the first harmonic modes of the string are being extracted fast.
The non-fixed string end means that the pitch of the string is not securely defined, at least, not when it is vibrating in the 'vertical' direction. I've actually measured string tones that had _two_ pitches close together, which can sound like a fret buzz if it's pronounced enough. At very least, with the string end too mobile, you get a slightly 'fluffy' pitch, which can contribute to the 'thuddy', noisy nature of the tone. I think this would tend to be more of a problem with 'scalloped' braces, which allow alot of top motion in the center, than with 'tapered', including 'parabolic', brace profiles.
From time to time you can also have the 'main back' resonance tuned so close to the pitch of the main top' mode that the two will 'beat'. This can manifest itself as a sort of 'chuff' on the attack, or, again, in particularly bad cases, can sound like a string buzz. I can tell you that this can drive you up the wall until you figure it out!
The most obvious solution for a resonance that causes problems is to change the pitch of it. Since these things are often fairly narrowly defined in pitch, just getting them to fall in between notes can help. Once you get off the peak the problems are much less. Shaving braces is one easy way to do this. You can also add weight, and sometimes that's a good way to find out if the problem is indeed related to resonance tuning. Poster adhesive is a good thing to use for a temporary weight.
If too much top motion at a particular pitch is causing 'feedback' issues with the strings you can try things that 'nail' the bridge down. Adding stiffness or mass in the bridge area will both reduce the amplitude of motion, and change the pitch. You will, of course, generally lose a bit of volume, and gain some sustain, from this, but that's not guaranteed. Both volume and sustain are more complicated than they might seem, but that's normal, isn't it?
To conclude a long post: the 'wolf' was originally the pitch interval that took in the 'Pythagorean comma' in 'just' tuning schemes. It was so far out of tune that it beat terribly, and was never played. A 'cello with a wolf note can beat in somewhat the same way, and that's probably why the bowed string guys picked up on the term. So, what's 'proper' usage?
|
Login
Register
FAQ
