Acoustic Guitar Ring

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

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.

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.

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.

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.

As mentioned above I bet it's the sympathetic resonance of the strings between the nut and the tuning pegs. I get that as well. Put some cotton up there to see if it goes away. I know it doesn't answer the question ("how to get rid of it") but at least next time you'll know what to do to not get it in the first place.