"Wolf" Notes

[Bob Womack]

And here is something that I haven't heard anyone speak to: Wolf notes and dead notes are not necessarily permanent features of guitars.

Here is where patience pays off.

Anecdotally: From the factory, my very lightly-built 1999 Taylor K-14 koa/cedar grand auditorium had a glaring dead note at F# on the first string. For the first year of the guitar's life it went thunk, thunk, thunk, when compared to the adjacent notes. However, once the pieces of wood figured out they were a guitar, it began to fade. By three or four years it was virtually gone. All the while I was using the same strings.

It is a hard thing to wait on an instrument to mature, but it can be worth it.

Bob

[Alan Carruth]

Richard284 wrote:
"Joe your description of a “thudding low sustain frequency” is exactly what I am experiencing with the F note on both the third fret D string and the 8th fret A string on my Martin OM-18V guitar on which I recently had a fret job."

Although that's a 'wolf at the F pitch' it's not the usual one. Normally the 'wolf' is at the 'main air' resonant pitch, which is around G on the low E, but often enough as low as F. Your's is at ~175 Hz, almost an octave higher, and is probably the 'main top' resonance. It's not an uncommon one, but much less problematic than the lower pitch. To check it out you need to find that 'top' resonance, which can be hard since it's usually masked by the 'air' pitch. When you tap on the top at the bridge you activate both of those resonances, but the pitch your ear reports is usually the lower one: your senses assume that the higher frequency is some sort of overtone.

To isolate the 'top' pitch by ear you need to block off the sound hole but without doing anything that would damp the top too much. One way is to put your fingers in through the strings and pinch the upper transverse brace and the end of the fingerboard with your fingers and thumb. With a bit of practice you can block off most of the hole without actually touching the top except at the UTB, where it's not vibrating much to speak of. Then you tap on the bridge in the center with the ball of your finger. This can alter the pitch a bit, since the top and the air are both working together on these resonances, but it will be close.

A more 'tech' way of getting this is to use a spectrum analyzer, such as 'Visual Analyzer' on a computer or the module in 'Luthier Lab', which is a new (and free!) Android app. For this you can simply damp the strings and tap on the bridge with the mic close to the top. The lowest peak in the spectrum will usually be the 'main air' resonance around 100 Hz, and the 'main top' resonance will normally the peak be more or less an octave higher.

It's interesting that the 'top' pitch often does not cause problems, even when it lines up perfectly with a played note. I have a 'test mule' guitar where the 'top' pitch is right on the fundamental of the open G string when the humidity is just right (or wrong, as the case may be...). I only spotted it when I noticed that the pitch was beating, coming and going in strength, in a spectrogram. Once I saw it in the data I could hear it happening, but nobody seems to notice it unless I tell them it's there. It appears and disappears with changes in humidity: it very perversely refused to show itself when I took the thing to a luthier's convention to use in a talk about wolf tones. When I got home it was there waiting for me. *sigh*

[Shades of Blue]

Dead notes and wolf tones are different phenomenon in my little closed off corner of the world lol.

I will say, I haven't noticed any wolf tones in my V Braced guitars....

[Dbone]

Originally Posted by Dbone

I'm dealing with one on the G string of a RainSong carbon fiber guitar right now and it is downright obnoxious. It is all I can hear in any chord involving an open G. Trust me, you will know when you have one. This one is quite bad.

Fortunately for me this guitar is getting replaced due to some fairly significant cosmetic issues with the instrument. Here's to hoping the replacement doesn't have the same issue.

Given that it is going back I have not tried changing strings, or anything towards trying to fix/influence the problem.

I have never experienced such problems until now.

Happy to report that the replacement did not have the same wolf note issue...Thank god because it was driving me absolutely bananas...

[poopsidoo]

Originally Posted by Bob Womack

And here is something that I haven't heard anyone speak to: Wolf notes and dead notes are not necessarily permanent features of guitars.

Here is where patience pays off.

Anecdotally: From the factory, my very lightly-built 1999 Taylor K-14 koa/cedar grand auditorium had a glaring dead note at F# on the first string. For the first year of the guitar's life it went thunk, thunk, thunk, when compared to the adjacent notes. However, once the pieces of wood figured out they were a guitar, it began to fade. By three or four years it was virtually gone. All the while I was using the same strings.

It is a hard thing to wait on an instrument to mature, but it can be worth it.

Bob

Bob you are a brave soul to play those same strings for four years. I change mine monthly!!

[Bob Womack]

Originally Posted by poopsidoo

Bob you are a brave soul to play those same strings for four years. I change mine monthly!!

Same brand. Har-har-har!

Bob

[canyongargon]

My 2017 OM28 when new had a bit of a dead note on the lowest A, particularly noticeable on the fifth fret of the low E. In the last two and a half years of playing the effect has lessened substantially.

[Alan Carruth]

Shades of Blue wrote:;
"Dead notes and wolf tones are different phenomenon in my little closed off corner of the world lol."

Physically the cause of the 'thuddy G' on the low E string of guitars is exactly the same thing as the classic 'wolf' note on a 'cello. The only difference is that on the guitar the string is plucked, while on the 'cello it's bowed. I don't have a wolfy 'cello handy, but I'd bet that plucking that note tends to give the same sort of 'dead' sound as you get on a guitar. Since the physics is the same, it just makes sense to look at them together.

To me, a 'wolf' note is any note that is adversely affected by a strong interaction with a resonance. The effect can range from the howling or growling of a 'cello wolf through something that sounds just like a fret buzz but isn't, all the way to a note that simply lacks the sustain of it's neighbors, and even some intonation issues. What counts is the cause in a strong interaction with a resonance, and the fact that it's a problem. Most responsive guitars will have some notes that are affected by such interactions, but if they're not problems they usually are just 'features'; aspects of the tone that make the instrument 'interesting'.

[tbeltrans]

Just to clear things up a bit, here is a REAL wolf tone...



If your guitar does that, then call animal control immediately and get out of the house pronto!

Tony

[Fredder]

I had the problem that the open G string produced the actual note 196Hz for a fraction of a second, followed by a sustained 392Hz tone. The G but an octave higher. The G on the low E string sounded just a little bit weaker than the F# and G#. Frequency analysis showed that the 196HZ overtone was missing.

I could reproduce this by playing the same note on the A and D string. When I played the G note there while muting the G string a spectrum analyses showed exactly the same thing. Subsecond 196Hz and a long sustaining tone of 392Hz. When I didn't mute the G string it started vibrating and the 196Hz tone also sustained.

Whenever I played that note the body of the guitar vibrated. It felt like both the top and the back.

Reading through these wolf note topics I tried various remedies with no success. Switching the bridge pins from ebony to bone to increase the mass of the bridge. Taping coins on various places of the bridge and body. I tried "teaching" the guitar the note by subjecting it to an hour of 196Hz. The only thing that did was make me hear a tone of 392Hz in every frequency sympathetic chord. Luckily the next day that was gone.
Nothing helped but I found things that made it worse like leaving the clip-on tuner attached to the head stock. I also noticed that minor adjustments to truss rod could make the G3 note even shorter. Changes in humidity also effected it a little(only noticeable on a frequency waterfall diagram).

I tapped the body to map the peak frequencies. It had one exactly at 196Hz. The other ones were between notes with the exception of one that was just a few Hertz shy of 440Hz.

I was ready to give up and then I had a stroke of luck. One of the tuners started acting up and I bought new ones. The originals were open back tuners with butterbeans buttons and I replaced them with open back tuners with ebony buttons. This dramatically improved the problem. Though it's still a bit weaker than the other notes the G3 note actually sustains. The thud is gone.

So what changed? These new tuners are significantly lighter than old ones. Going by the spec of both tuners the difference is almost 40 grams.

I did the tap test again and that peak at 196Hz is still there.

There must be some coupling effect going on between the neck and the body. When tuning the G string I can feel it vibrating in the tuner button more than with the other strings.

[davenumber2]

I recently had the problem of the open A string and the fretted A at the 5th fret, 6th string just going thunk on a new OM sized guitar. After reading up some it seemed like a main air resonance issue. I ordered a D'addario O-port in order to change the size of the soundhole (no guitar modification required). I did have to modify the O-port to accomodate soundhole pickup controls. It immediately took away the problem and made the sound feel more solid with an increase in bass, overall the guitar just seems to ring out better. I was skeptical when buying it but thought I'd give it a shot. It's fairly innocuous and I don't mind how it looks with it. It may not work in every situation or guitar but it helped mine immensely.

[Tom60]

Some dead notes are always there, on any guitar - just the matter of the beast.

They follow the size of the body - the highest I know of is on my smallest guitar, the LG-2 Tribute CS Gibby - on B, and the lowest I recall was on HD35, on E, (rendering it useless for most tunes in the tuning of E)
other guitars somewhere in between, 000s and OMs on A, dreads on F sharp or F (D35) ... so it goes...

You have to find your way around it, but no stop gap measure will cure it..

E.g. - I know I cant play Babe Im gonna leave you on 000-18, no matter how great she sounds overall... the open A string doesnt ring like it should.. or Jeff Beck´s Rock Me from Truth (in B) on the LG2 - without that THUD dead sound

.. horses for courses


/btw electrics are no exception, as they are guitars too - all genuine Gibson Les Pauls have a weak(er) sounding Bb/B on G string in 3rd/4th pos.... I once had to return a great R7 just for that - that note was completely dead../

[Fredder]

Originally Posted by Tom60

Some dead notes are always there, on any guitar - just the matter of the beast.

They follow the size of the body - the highest I know of is on my smallest guitar, the LG-2 Tribute CS Gibby - on B, and the lowest I recall was on HD35, on E, (rendering it useless for most tunes in the tuning of E)
other guitars somewhere in between, 000s and OMs on A, dreads on F sharp or F (D35) ... so it goes...

You have to find your way around it, but no stop gap measure will cure it..

E.g. - I know I cant play Babe Im gonna leave you on 000-18, no matter how great she sounds overall... the open A string doesnt ring like it should.. or Jeff Beck´s Rock Me from Truth (in B) on the LG2 - without that THUD dead sound

.. horses for courses


/btw electrics are no exception, as they are guitars too - all genuine Gibson Les Pauls have a weak(er) sounding Bb/B on G string in 3rd/4th pos.... I once had to return a great R7 just for that - that note was completely dead../

The F through G on the E string and the open A string are due to the air resonance of the body. The problem is that those low notes are very close together in frequency. Sometimes the closest note gets sucked towards the air resonance frequency. I have noticed guitars(with properly cut nut slots) were it was impossible to get a G on the low E that was in tune.

The biggest issue is that it seems to be more noticeable on the more expensive instruments and once you start hearing it you can't unhear it. I hope the wolf stays away.

[Alan Carruth]

Fredder wrote:
"There must be some coupling effect going on between the neck and the body."

Bingo. As usual with the guitar, though, it's bit more complicated than it might seem, and that's actually one key to your particular problem. You wrote:
"The G on the low E string sounded just a little bit weaker than the F# and G#. Frequency analysis showed that the 196HZ overtone [actually, that's the 'fundamental', AC] was missing."

"Whenever I played that note the body of the guitar vibrated. It felt like both the top and the back."

The lowest frequency resonance on the guitar that can actually radiate sound effectively is the Helmholtz-type 'main air' resonance. Air is moving into and out of the hole, changing the pressure in the box. The frequency is largely determined by the box volume, which sets up the elasticity of the 'spring' and the hole diameter, which determines the mass of the air 'piston' bouncing on the spring. Helmholtz worked out an equation for finding that frequency on glass bottles and such, but it doesn't work on guitars because the flexibility of the walls changes the 'spring' action. At the 'air' frequency the top (especially) and the back (usually) move a lot, pushed around by the pressure changes, and you can feel it.

On many guitars the resulting air resonance happens at a frequency that's pretty close to G~196. This often makes the guitar such an effective sound producer at that pitch that is 'sucks' all of the energy out of the string at that frequency and converts it into sound very quickly. You get a note that's twice as powerful for half as long. Out ears are lousy at picking out even fairly large changes in sound power; it barely sounds any softer, but you sure notice the lack of sustain. This is the most common guitar wolf note.

The Helmholtz mode is the lowest pitched 'air' resonance, but there can be other resonances in the structure of the guitar even lower. One of these is the 'first corpus' mode, where the entire instrument vibrates like a xylophone bar in it's fundamental mode. There are two stationary 'nodes' for this; one is usually around the nut or first fret, and the other is generally a line across the lower bout near the wide part. If you laid the guitar down on pads at those points on a table and tapped on the top of the head you could get that mode going. As the head and tail block are moving 'up' away from the table top, the neck block goes 'down'. The frequency is a product of the stiffness and mass of the whole guitar, but the neck does bend a lot, and has a big effect on it, so this is often simply called the 'neck mode'.

It's easy to hear this. Hold the guitar up by pinching the neck between your thumb and finger, right up at the nut, with your finger across the fretboard to damp the strings. Try to allow the guitar to vibrate as freely as possible. Hold it up so that it hangs freely, with the top of the headstock near your ear, and tap on the head with your finger tip. You should hear a pretty clear pitch. On many guitars this is quite low in pitch; down around D~150 Hz, or lower, but in some cases it can actually be high enough to match the Helmholtz-type 'main air' pitch.

When that happens the two can 'couple'. As the head and tail come 'up' the top and upper surface of the neck are in compression along the length of the guitar. Since the top is almost always bowed upward anyway, either by construction or because of string tension, this pressure pushing in on the ends of the top causes it to puff up even more, and suck a little air in at the soundhole. As the head and tail move 'down' the air is pumped out. This is what the 'main air' resonance does.

In situations like this, where you have a pair of coupled resonances, things get complicated. Basically the two of them will trade energy back and forth in a range of frequencies around their resonant pitches (which have to match pretty closely, but need not be exact matches). Either part can 'store' energy at some pitch and feed it back for the other to use in producing sound. If you look at a sound spectrum in that range there will be two peaks in output with a dip in between, rather than the single tall peak that you usually see with just the 'air' resonance. Instead of one powerful (and short lived) note you can get two that are pretty powerful, but still have decent sustain.

Remember that the head moves a lot at the 'neck mode' pitch. The mass of the head can have a big effect on the pitch of this resonance. In order for the two resonances to couple effectively the pitches of the two modes have to match closely; if they're within 5 Hz or so they can couple strongly, but if they're 10 Hz out you lose most or all of the effect. A change of 40 grams on the headstock can alter the pitch 10 Hz or even more, and can certainly be enough to make the difference.

I think this is one reason why people argue about the tonal effect of tuning machines. Necks vary in stiffness, so the 'neck mode' on different guitars can cover a pretty wide range of pitches. The 'air' mode varies too: anywhere from F# to A or even a little higher. If you have a guitar that's 'close', and change something on the head, it can move into or out of coupling range, and the sound changes noticeably. You report this, and somebody else tries the same thing, but since his guitar is not like yours, it doesn't work. Once you understand it the explanation is fairly simple, but if you don't it's just confusing.

[Tom60]

Originally Posted by Fredder

The F through G on the E string and the open A string are due to the air resonance of the body. The problem is that those low notes are very close together in frequency.
I have noticed guitars(with properly cut nut slots) were it was impossible to get a G on the low E that was in tune.

It is the D string in mid positions where it sticks out worst.. and that´s what I´ve meant.. not the low E.. there it is much less noticeable

But I agree about the G on E string - it is a problem on its own.. I always have a hard time to tune it right .. on short scale guitars anyways, it is never quite right