For about a month, I have had a strange problem with my piano; first, I will provide the data:
the subject:
the piano is a Brodmann 128 PE purchased a little more than 2 years ago; I use it about 3 hours a day; tuning performed approximately every 6 months, the last one around mid-October with A4 at 442 Hz.
The tuning still holds (I verified against 442) except perhaps for a very slight misalignment of some unisons.
the fact:
I don't know if the resonance was there before and I didn't notice it; anyway, following my teacher's request to play some Chopin parts as softly as I could, I noticed that E3 left a resonance tail once the key was released (without pedal). In fact, Eb3 resonated even more, and something can be heard starting from B2 up to E3, with maximum resonance on Eb3. I then examined the hammer action thinking about dampers that weren't pressing correctly; instead, they all work fine.
the empirical tests:
the resonance is not at the frequency of the note, but rather on some partials or higher harmonics, very high-pitched (I would say in the octave 6 area or higher and therefore annoying); I tried pressing Eb3 and releasing it immediately, and the resonance (audible - with f or fff - for over 2 seconds) can only be stopped by touching the upper part of the strings with a finger (i.e., between the dampers and the tuning pins); at this point, only a faint echo of the soundboard remains for a moment, but at a much lower frequency (practically the tail of the note that is not annoying). Even when using the practice pedal, the resonance is present; in practice, it's enough to strike the string.
If possible, I would like to avoid calling the tuner before next spring; in the meantime, I would be happy to receive advice on what is happening to me.
Have you tried applying light vertical pressure to some of the dampers? It seems to me that one (or more of them) is not holding the strings firmly in place.
Or if the action has been disassembled, some dampers might not have been repositioned correctly. Some are transversely bisected; the upper part might have been positioned well while the lower part skips a string. In this case, harmonic sounds develop but they are very evident! It is probably as Sergio says...
I checked the dampers and they press all the strings correctly; I even pressed my finger on the damper immediately after depressing the key. The resonance is still there. 😳 In practice, it behaves as if the damper were the rigid attack point of the string: I believe the upper part of the strings, between the dampers and the bridge/tuning pins, is going into resonance; in fact, the resonance (very high-pitched) stops if I place a finger directly on this section of the three strings.
Anyway, I found an acceptable temporary solution: I placed a strip of adhesive paper (the kind body shop workers use) across all the strings from B2 to E3 about 3 centimeters from the top; this way the paper absorbs part of the resonance; of course, the tone quality is naturally a bit darker (due to the reduction of many partials), but the resonance is reduced to minimal fractions of a second and is no longer so annoying. Additionally, I pricked the hammer felts a little with a small pin to soften the impact against the strings. Now even Chopin's pp are feasible without the ear suffering (at least because of the piano; the suffering due to the pianist's interpretation remains, for which adhesive paper is not enough). 😉
Of course, I would like to find a definitive solution; if there are other ideas, I am ready to try them!
Don't use the "little nail." Use needles if necessary. It could also depend on the voicing of the hammers. If the grooves on them are very evident, the sound may have become so harsh that it sounds "metallic." Therefore, a "competent" technician needs to check the voicing, as you suspected. Furthermore, the vibration could come from poor contact of the strings on the bridge. You can intervene here as well. Use a brass bar and gently tap the strings with a small hammer at the bridge. The vibration might disappear. However, be careful when handling the hammers. Voicing is a difficult intervention with irreversible results.
Thanks for the advice; I have carried out all the recommended tests, I tapped the strings on the bridge, but nothing changes; I pressed on the damper, nothing (the action is Langer, but at this point I don't know if that has anything to do with the resonance?)
So I put rubber wedges between the strings to see which of the three Eb3 strings resonated the most: the middle one seemed noisier to me: so I detuned it by loosening it a bit and then retuned it; the resonance remains for all frequencies!
I put a hand on the strings of the 6th and 7th octaves to be sure that the resonance was not coming from other strings not protected by dampers: it comes precisely from the Eb3 strings. I tried some percussive notes in fff on the Eb3 with a stopwatch and the resonance lasts a good 6 seconds... definitely too much. Doing the same test on the neighboring F3, the resonant sound lasts less than 1 and a half seconds.
In fact, when playing, it is better to keep the sustain pedal depressed when using the Eb3 so that the fundamental sound covers the annoying resonance.
Now, to play, I have put strips of sandpaper back on the offending section of strings: it's better to lose the harmonics than to hear that cursed resonance, at least until I have to call a good technician. I am afraid that this time I won't get away with the usual 70 euros for tuning! Assuming a solution is found. 😉
Considering also the courtesy with which you responded in the past to my question in the first post regarding the resonance on the Eb string section above the dampers, I feel it is only right to let you know how it ended up.
Until today, as already mentioned, in addition to performing all the tests that were kindly recommended to me, I had found a compromise by empirically reducing resonances with pieces of gummed paper attached to the strings concerned (which, however, changes the sound timbre for the worse).
Today, a tuner finally came, whom I found after various searches over time in piano shops where I had presented (almost always in vain) the problem, and who practically solved this resonance for me.
In fact, after careful tuning, he hypothesized that the damper was falling exactly on the "node" of the standing wave resonance of the strings, and since there are practically no vibrations of the standing waves themselves at the node, its pressure (even if increased) was almost useless. So, he moved the damper just a few millimeters higher, so that it would cover at least in part the "belly" or "antinode" of the standing wave that previously continued to vibrate even with the damper lowered. In this way, the resonance has decreased significantly and practically no longer causes annoyance.
Well! I hadn't thought of this solution! Long live tuners!
P
Pianoaccordatore
Reply 9 by Pianoaccordatore
Well.
In fact, sometimes the cause of a chirp or strange resonance can depend on the damper.
Indeed, in some upright pianos there is little space in the string crossing area to be able to choose the right point for the damper, and sometimes this generates an inevitable non-optimal choice of the damping point, causing precisely a strange resonance or chirp.
you are absolutely right. I was wondering... in general, couldn't the damper be lengthened with a longer felt so that it covers a larger part of the strings and be less subject to the criticality of positioning? I heard that some Steinways have such a system.
P
Pianoaccordatore
Reply 11 by Pianoaccordatore
as a remedy, it is generally preferable to try slightly shortening the damper felt that generates an odd harmonic, i.e., dissonant.
The cause of a strange resonance could also depend on the fact that the damper in question does not rest simultaneously with every part of it on the string.
So in this case, bend the metal slightly under the head of the damper to make it parallel to the string.
