Pianotech

  • 1.  Plate noise?

    Registered Piano Technician
    Posted 10 days ago
    Hello.

    I heard a strange sound that was like an odd ringing.  I first I thought something was on the soundboard.  I checked with the soundboard steel, I looked around with an endoscope, tighten plate bolts.  I finally got my stethoscope out and checked different spots on the piano.  I find it's loudest coming from the plate next to the two notes that cause it, F5 and F#5.  When I play the note or pluck the string, immediately there is a metallic ring in two parts, one loud then soft.  Kind of  like "OO-oo".  (Imagine a metallic pigeon coo-ing.)  The stethoscope picks it up in the cabinet rim also.  There is no lock on this piano, but it sounds a lot like that.

    It isn't so bad that just having the lid down helps.  It's pretty much when the lid is up and I'm tuning.

    Thanks for your suggestions.
    Robert

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    Robert Callaghan RPT
    Reno NV
    (775) 287-2140
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  • 2.  RE: Plate noise?

    Registered Piano Technician
    Posted 10 days ago
    A Long time ago someone had something similar on an upright piano. I believe he solved the problem by attaching a large magnet to the plate. I’m not sure why he came up with that solution but it had something to do with a sympathetic resonance of the plate.
    Try it.

    Wim.

    Sent from my iPhone




  • 3.  RE: Plate noise?

    Registered Piano Technician
    Posted 10 days ago
    If grabbing one of the struts stops it, a large magnet attached will change the frequency of the sound and hopefully make it tolerable.

    Peter Grey Piano Doctor

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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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  • 4.  RE: Plate noise?

    Registered Piano Technician
    Posted 9 days ago
    There are several potential causes and several different solutions. You don't indicate the brand or type of piano, which would help. So, some generic suggestions. First, check termination points.
    • For example a bearing bar that is slightly flat where the string(s) pass over.
    • A bridge not properly notched can buzz when the wire vibrates. 
    Yes, gray iron castings can, and do, resonate. If this is the case there are, again, several options.
    • As already suggested attaching a magnet will add mass and at least change the resonant frequencies, perhaps getting them out of an annoying range.
    • If one of the struts is resonating (and the piano is a vertical or the client doesn't mind) magnets can also work here by adding mass. How much mass? You'll have to experiment. 
    • Another possible solution for resonating struts is to add a strip of hardwood to the side of the strut. This can be attached using 3M double-sided foam adhesive strips. Note that this may be irreversible given the strength of the adhesive. Use an attractive wood and finish it before applying. Done well it can almost look intentional (from the factory). 
    • Another method of attaching wood strips is to clamp them in place and drill through for small screws or bolts. In this case you will need to put a layer of thick bushing cloth (or something like Ecsaine) between the wood and the strut.
    • Experiment -- using lightweight clamps, clamp the strips in place first to see if they give the results you want.    

    ddf


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    [Delwin D] Fandrich] [RPT]
    [Piano Design & Manufacturing Consultant]
    [Fandrich Piano Co., Inc.]
    [Olympia] [WA]
    [360-515-0119]
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  • 5.  RE: Plate noise?

    Member
    Posted 9 days ago
    Del... why not countersink some round magnets into the wood flush to the surface instead of adhesives and velcro or screws ? the magnets can be superglued in although you can get some magnets drilled with holes to put screws in.

    I have encountered a bell like sound in a number of Yamaha grands in the bass end near a strut. I believe the piano is a C3 Conservatory

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    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    (843) 325-4357
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  • 6.  RE: Plate noise?

    Registered Piano Technician
    Posted 9 days ago
    Good idea as long as they are strong enough. There still needs to be a buffering layer between the wood and the strut.

    ddf


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    [Delwin D] Fandrich] [RPT]
    [Piano Design & Manufacturing Consultant]
    [Fandrich Piano Co., Inc.]
    [Olympia] [WA]
    [360-515-0119]
    ------------------------------



  • 7.  RE: Plate noise?

    Registered Piano Technician
    Posted 9 days ago
    In the same way that small vise grips can be used on bridge pins to diagnose mass loading needs and methods, a padded C-clamp works well as a diagnostic tool for plate resonance issues. One is simply looking for "change" rather than total elimination (usually).

    And the problem may not actually be in the plate.  Try masking off all aliquots and NSL sections and listen. If a beneficial change occurs gradually lift the masking section by section until the problem re-emerges. Then you know what to do. If no change at all then you've eliminated that possibility.

    Peter Grey Piano Doctor

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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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