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I have a problem my technician has been unable to resolve. When I play certain notes, I hear a snapping noise. It sounds like two pieces of wood being slapped together. It's quite noticable on the highest A-flat, so we looked searchingly at the hammer for cracks and looseness and saw nothing. He popped the hammer off the shank and re-glued it, but that did nothing. No loose screws there, either. I hear the noise when I play most of the notes in the octave above middle C. It's inconceivable that all the hammers there have the same coincidental crack. Unfortunately, the problem in that octave hid behind the piano while my technician was here, but it snuck back out again as soon as soon as he left.

Any ideas?

Paul,

Type of piano (grand, vertical, spinet)?
Model?
Age?
Playing conditions? (playing loud, soft, etc.)
Pictures of piano (inside and out)?
Room conditions (humid, dry, hot, cold)?

There are several possibilities. A more exact description would be helpful such as does it happen every time you repeat the note, at every loudness level, etc?

Offhand one common thing that occurs to me- in the offending region of noise, try pressing down one note in the middle of that region and hold it 'bottomed out' with a fair amount of force, like a few pounds of downward pressure. While holding it down, try the surrounding notes. Does that make the problem go away?

Ah, good point, Frank - no details! The piano is 1908 Mason/Hamlin AA, completely rebuilt 2 years ago by both Faust and Harrison. The piano has a Dampp-Chaser underneath, and I have humidified forced-air heat and a room humidifer. I monitor the humidity in the room and underneath the piano with often-calibrated humidity meters, and they typically match within 2-3% on average, with short-term fluctuations. I have had a few room-humidity drop-outs lately - perhaps that's important.

Brick: good idea for a test. After my wife finishes her nap, I shall do just that. If I make noise now, she will make a snapping noise on my head.

Key frame bedding might need some attention.

Onr thing I've done before is to remove a known good hammer and shank and place it into the position of the one making the noise. You can eliminate the hammer as being suspect or verify that it is the problem right away.

It sounds like what Curry said above though. If you hold a suspect key down and thump it firmly with your fingers, you will hear a slap if the action frame is not properly bedded.

I suggested to my technician that we try a different hammer on the high A-flat, but I forget whether we actually did this. The next time I open up the piano, I will try this.

I tried holding down neighboring keys in the octave above middle C while striking one of the snapping keys. It didn't have an effect, although I didn't press really hard. I'll try that. Right now, I can't, because the problem is hiding again - it knows we're looking for it.

What I did notice is that, if I hold down E and play F, the E string resonates at the pitch of E. That should only happen when the note played has a harmonic that coincides with the frequency of the un-damped string. I don't understand. Perhaps my entire understanding of physics is wrong, my professional life in science a fraud, my whole existence a pathetic lie....Naaahhh.

I forgot to mention that this piano has a Quiet-Time system installed. I listened for the snapping noise as I gradually engaged the Quiet Time bar, but there is no indication that any hammers are hitting it until it is almost fully engaged.

Try things more in slow motion and try to describe when the snap occurs. IOW, before the hammer starts it's upward travel, during upward travel, at the exact moment it hits the string, as soon as you let go of the key, when the hammer falls to the bottom? etc

You might check the hammer pinning. Extremely loose pinning can sound just like a loose hammer head.

Find a hammer which clicks, take it off of the rail, hold it by the flange with the hammer pointing down, lift the hammer shank up, let go and count the number of swings before the hammer comes to rest. If it's over 10, repin and see if the noise goes away.

There is some diveristy of opinion on this, but in general, 6 to 8 swings is what most technicians recommend.

Good luck,

Tom

Tom, we checked the pinning on the snappy A-flat. It was not loose. It doesn't make sense that all the hammers in the octave above middle C have a pinning problem.

Brick, it's very hard to tell exactly when the noise is made, but I'll listen in slow motion.

If there is a key frame bedding problem you may try playing one note up there hard while looking at the other keys and hammers in the offending octave. If the hammers are all moving slightly the glide up there is slightly low and if the keys all slightly moving the glide is slightly high.
E and F do have coincident partials but it would be quite a ways above the top octave if this is where the resonate note is. Take a look at the F hammer to see if the left edge of it may be hitting the right string of E - if there is a hammer string alignment problem this gives you more stuff to look at for noise sources.

After all, the strings are connected through the bridge. Motion in the bridge will excite nearby strings.

As for your problem, the keyframe seems likely. Sometimes you can remove the keyslip and press on it and feel the frame bend and touch the bed. However, the glides may not be set properly, or some rails, particularly the damper stop rail, may have come loose, or the dogs that hold the back of the keyframe. There are a lot of possibilities which are hard to think of when you are not looking at the actual piano.

If moving the una corda pedal a bit changes the sound, then keyframe bedding is a likely candidate.

--Cy--

Thank you all for your comments. I'll let you know if we figure this one out. In the meantime, the problem knows we are talking about it, because it has gone away again.

That puts more certainty toward the keyframe bedding issue that a few of us have had in mind.