Trombone "ringing"/unwanted resonance from lower slide

[diminishedSeventh]

I've recently started noticing some ringing specifically in 2nd and 3rd position(s) across my horn and realized that it is coming from between my lower outer slide and receiver. When I flip the outer slide, the ringing goes away. Anyone have any ideas what could be the issue?

I've read older posts where they suggest checking the slide lock but I've tried messing around with it to no avail.

[ghmerrill]

Often this can happen when a solder joint breaks or becomes cracked -- sometimes in a joint to one of the braces. Could be the water key and it just seems to be from somewhere else. If you've got a bell with a bell wire, it could be from that. Or a loose screw in a valve linkage. Or a solder glob in one of the slides that has finally come loose a bit (those can be real hard to find). It's easy to misidentify the location.

Finally, it can be a vibration not in the horn at all, but from somewhere else in the room that just SEEMS to be in the horn. I've had that happen more than once.

It can be difficult to find by yourself because you need to perform a "laying on of hands" (while playing the right pitches) to see what stops the ringing/buzz/vibration. When I can't find it myself I get my wife to stand beside me and localize the vibration while I make it happen.

[tailgate]

Check spitvavle pivot screw and spring. Tighten if needed. Lubricate.
Check slide bumper for tightness.
Lube moving parts.
Sometimes moving parts develop some play/slop. Lubricant takes up the play.

I recently had a trigger roller on dependent Bass start to vibrate unless lubricated.

[Crazy4Tbone86]

I’m not quite understanding the description of where the sound is coming from. The OP states “it is coming from between my lower outer slide and receiver.” Does “the receiver” refer to the bell receiver? If yes, is the sound coming from the lower cork barrel? Is the sound coming from the tapered male tenon? Both of these seem to be strange places for air leaks because the inner slide is usually a continuous tube directly through those areas. Thus, we can probably rule out an air leak.

I have had trombones in which the knurled ring on the end of the lower cork barrel was threaded and removable. Is that a possibility on this horn? I have also had horns in which the spring or corks/felts in the cork barrels were very loose and rattled while I played.

[diminishedSeventh]

If yes, is the sound coming from the lower cork barrel? Is the sound coming from the tapered male tenon?

From as best as I can locate it, it seems to be coming from the tenon, yes. I get some interesting feedback from over/undertightening the tenon ring. Under-tighten and the resonance(s) (at specific frequenceis) that I mention becomes more noticeable, and over-tighten I get more resistance at those same frequencies.

[diminishedSeventh]

It can be difficult to find by yourself because you need to perform a "laying on of hands" (while playing the right pitches) to see what stops the ringing/buzz/vibration. When I can't find it myself I get my wife to stand beside me and localize the vibration while I make it happen.

A "laying on of hands" test is what helped me narrow down that the weirdness was coming from around the bell receiver, although I struggle to remedy or precisely identify what is causing it. I've enlisted help from friends and family to see what the notice, but they have all told me they don't hear any ringing from in front of the bell, so I believe it's something that I am noticing exclusively from behind the bell.