Hi,
After recording an acoustic guitar, double tracked, one slightly to the left and one slightly to the right, it sounded great, then listening closer I can hear a slight high pitched ringing from it, anyone any ideas how to get rid of this ?
 
Thanks
John

I've had this problem as well with acoustic guitar, certain overtones ringing much louder than others. At first I thought it had to do with mic placement or the acoustics of the room I was in, but, after a fair amount of experimentation, I've come to the conclusion that, at least in my case, unfortunately, it's the instrument itself and is the phenomenon known as "wolf tones". Here's how Wikipedia defines it:
 
A wolf tone, or simply a "wolf", is produced when a played note matches the natural resonating frequency of the body of a musical instrument, producing a sustaining sympathetic artificial overtone that amplifies and expands the frequencies of the original note.
 
I've had some success taming these with EQ, using notch filters, but, if you happen to own iZotope's RX, its Attenuate feature works very well and has the advantage of being able to attenuate in relative proportion to adjacent frequencies, if you set the Direction to Vertical. This sounds more natural to my ears, as it then only attenuates as much as it needs to based on context, though, again, a notch filter can yield usable results as well.
 
Hope this helps.
 
 

benjaminfrog
phenomenon known as "wolf tones". Here's how Wikipedia defines it:
 
A wolf tone, or simply a "wolf", is produced when a played note matches the natural resonating frequency of the body of a musical instrument, producing a sustaining sympathetic artificial overtone that amplifies and expands the frequencies of the original note.
 

That is indeed the classic definition of a "wolf note" or "wolf tone", originally used in describing a behavior of bowed string instruments. The coupling of the played note to the body resonance of the instrument creates a loud, sometimes wild and hard to control note (if it is not exactly at the frequency of the desired note). Energy provided by bowing quickly and easily dissipates into acoustic energy, hence the wolf note is louder than surrounding notes. Due to the bowing (= contiunous excitation) the wolf tone sustains.

The same phenomenon occurs in plucked instruments as well. But in plucked instruments, the excitation is a momentary impulse (the pluck). The energy of the pluck easily feeds the instrument's natural resonance frequency in a wolf note, it dumps the energy rapidly as before, resulting in a strong note, perhaps somewhat detuned if the natural instrument resonance is not exactly at the frequency of the desired note. This part is no different than above.

But where a plucked instrument differs from a bowed instrument, is once the energy of the pluck and coupled resonance is rapidly dissipated, there is no additional sustaining excitation as is provided by the bow. Because of this, the note rings for a shorter period of time than other notes. The typical perception of this in a guitar type instrument is a note that sounds "thuddy" and "odd" rather than clean and ringing. On guitars this typically occurs around the frequency of the open G string. Play some notes around that area, and you may find one that sounds different than the rest - thuddy and odd in some other way. This is your wolf note. If you're lucky, your instrument will happen to have (or by design in hand-made instruments) a resonance between musical pitches instead of exactly at one, and this well reduce the effect, and the wolf may be far less noticable.

So there's everything you never wanted to know about wolf notes in plucked instruments!

Regarding the OP's question, it's hard to say without hearing the issue, but sometimes weird higher resonances can be caused by strings vibrating behind the nut or between the fretted fret and the nut, or sometimes if a string ball isn't seated properly against the bridge plate, it can vibrate. Also, poorly made nuts and saddles without a good break can cause wierd things to happen, as can something loose in a tuner.

It almost sounds like feedback, but it's not that !

So "feedback" means it sustains rather well, right? If so, it would not be wolf tone related, as they dump their energy fast - fast decay.

Does it occur at one pitch no matter what notes/chords you're playing? Or does the pitch of the "feedback" change with different notes/chords?

Are the more troublesome notes/chords up higher on the neck (like a barred chord)? If so, is the problem still there if you damp the strings between your hand and the nut (may require a third hand or stuffing something under the strings)?

Sorry this doesn't really help with eliminating/reducing the sound on your recording, but it may help to figure out how to prevent it in future recordings.

Much depends on which frequency band the problem is in. If it's outside the main frequencies occupied by the guitar then it will be easier to deal with or at least minimise. If it sits right in the middle of the music then it'll be much harder to deal with. This is one of those jobs where it's often better to use two or more techniques each having a little impact than using one big process. If the offending noise tracks the guitar pitch then it might be almost impossible to get rid of.

If it's well clear of the guitar's main frequency band you could try a gentle low-pass.

You could try setting up an eq to have a boost then sweeping it around until it emphasises the problem frequencies then cutting as narrow a band as you can get away with at that point.

Another possibility is multiband compression just compressing the frequency band in question or perhaps a suitably tuned de-esser. Side-chaining a multiband comp or de-esser using a synth-created audio track containing the relevant frequencies might also work.

A final possibility that comes to mind is if you have a noise-reduction plugin (or Audition, Wavelab or similar) that works by taking a noise print from the audio then removing the noise-print frequencies what might work is cloning the track twice and equing one clone so that there's pretty much nothing but the offending noise in it.

Then put some of that noise-only track at the beginning of the other clone, export it into the sample editor and run the sample editor's noise reduction on it (a few times at low settings is generally least obtrusive). Then import that audio back into the project in a new track and use that as the guitar track for mixing purposes.

In reality you're likely to need a combination of methods. Not a quick or simple job unfortunately.

Did you own X2? If so do you own R-Mix? You may be able to get rid of that ring rather easily using the Noise Cancel (try the AirCon setting... it seems to yank some ringing type stuff) or just isolate the ringing "blobs" with the Circle tool and turn it down.
 
Might work. Just an idea.

Could this be caused by "reverb" ?
 
John

jwh
Could this be caused by "reverb" ?

Not sure why you have reverb in quotes, but if you mean a reverb plugin, solo the track with the reverb plugin bypassed and see if it goes away. Or solo the track with reverb only (100% wet) and see if it's in there but not the totally dry signal.

If you mean "reverb" as in some natural phenomenon, I would think that in most home studio situations it would be unlikely to get a "feedback-like" sound.

TO me the hardest part is trying to figure out where the ringing is coming from. It could be from the instrument, the recording equipment or something in the room. I suppose it could also be from the interaction of the 2 guitar tracks. Does the sound persist if you kill one of the guitars?