longitudinal mode?

[Richard Brekne]

Well, its not anything to do with the longitudinal mode. For such a high 
string thats out of the question.  You might check the cross strut.  I 
had a D here in town that was causing a similar sound on C6.  Only C6 
would excite it... but when you played C6 reasonably hard boy was that 
buzz loud. Three techs tried different things including one who decided 
to mash the strings into the bridge surface in what was the most 
aggressive string seating job I've seen in a long time.  Another tried 
tightening the <<bell>> screw which very temporarily fixed the 
problem... which pointed me in the direction of the cross strut when I 
got finally called.  A bit of banging around with the palm of my hand 
and I found that the cross strut was the culprit.  I ended up removing 
the thing, bushing the ends with some thing felt and reinstalling it 
with as tight a screw as I could get.  Problem disappeared permanently.

Buzzes can come from all kinds of places however... in and out of the 
instrument... and you could swear you hear where its coming from and be 
totally wrong.  Hinges are likely culprits as is the lock mechanism.  
Good luck hunting it down.

Cheers
RicB


    I tuned this piano again a few days later for a master class.  The
    lid had been restored and the percussion equipment was all gone by
    that time.  I could not find that elusive buzz anymore.  Either
    something in the hinges (hinge-pins?) was sympathetically vibrating,
    or more likely the snares right up close to the rim were doing
    it.  Funny thing is, I could of sworn it was coming from inside the
    piano.

    Chalk another one up to "experience"
    Andrew Anderson

    At 07:36 PM 9/30/2007, you wrote:
     >All strings of the unison excited the same short buzz about an
     >octave +.  Had me chasing around a while for something but I
     >couldn't isolate a sympathetic resonance.  I didn't think of lifting
     >because all three were making the sound.  I could try it.  I did
     >lift and level these strings last year.  The piano is on full
     >climate-control with a cover most of the time and there has been
     >very little variation in pitch.  I noticed it today with the lid
     >off.  It was right next to the snares but the sound sure seemed to
     >come from within the piano.  I'll have to check again when the
     >orchestra instruments are distributed back to their classrooms/owners.
     >
     >Andrew Anderson
     >
     >At 03:36 PM 9/30/2007, you wrote:
     >
     >>>Tuned a D this afternoon to prep for this afternoon's
     >>>concert.  A#6 had a short buzz a harmonic above the note.  I could
     >>>not find an offending duplex (front/back) to mute.  Would this be
     >>>a longitudinal mode?  Got any ideas to chase this one down?
     >>>Andrew Anderson
     >>
     >>Hi Andrew,
     >>I'd think not. The longitudinal would be way up there in pitch, and
     >>I'm not sure they're even audible that high in the scale. Did you
     >>isolate unison strings to see if only one made the noise? I'd try
     >>repositioning the strings a tad, and lifting and leveling that
    unison.
     >>Ron N