Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Partial strength - hammer voicing or soundboard ?

In your experience, are relative partial strengths primarily a function of hammer voicing or soundboard/bridge impedance/resonance ?

I find significant variation in the relative strengths of the lower partials in the tenor/bass section of my piano.

(Edit: Ignore, for the moment, strike point, and assume constant velocity hammer strike.)

With wound strings, there are significant differences from string to string in spectrum balance. Plus longitudinal modes can act out in this area. But the hammer is about half the game.

A lot of older pianos have really hard hammers which emphasises the harmonics. If volume isn't the main issue, try softening the hammers.

Harmonics are an artificial construct which reflect the way that a waveform is approximated by a Fourier series. The waveform depends on the initial conditions of the wave, that is, the shape the string is when it begins to move. That shape is determined by the hammer. Later, it may be modified by the impedance of the bridge and soundboard.

In my experience, so far, relative partial strength is primarily a function of the hammer weight, strike point shape/surface-area, and hammer hardness/squishiness/resiliency.

Soundboard/bridge/rim impedance/resonance issues deal more with the system's ability to disseminate the tonal energy: the more flexible the system, the greater potential there is for louder attack sounds--but there will be less energy left over for the decay portion of the sound envelope. However, there is also a tonal influence: flexible systems allow for a boomier/bassy tone, and conversely, stiffer boards result in a thinner sound--yet have greater sustainability/singing-tone.

My ear clearly hears that some third partials partials are louder than the fourth partial. On adjacent notes, the fourth partial is louder than the third.

There is little point in choosing a 6:3 octave for A2/A3 if the fourth partial of A2 overwhelms the third partial A3. Yet, G2/G3 might be better with a 6:3 octave if the fourth partial of G2 is weak. It would seem that a talented voicer might be able to even out the differences enough that one could have a more consistent stretch.

One other point. I would think that a soundboard exhibits a variety of resonant modes, some of which might enhance the transfer of energy to the soundboard, while at other frequencies the transfer would be inhibited. This would also seem to affect perceived partial strengths.

Try as I might, I have never found a published source in the realm of physics, acoustics, music, or electronics that states harmonics are an artificial construct. Please cite at least one reference that supports your claim. I figure if I can hear them, they are real to me.

Well, I suppose the formulation was a little clumsy. If taken literally, some atheists say "I AM the harmonics !"

Prout that means you have the "Fourier on my mind" syndrome.

Harmonics are no artificial construct.

They are identifiable and elicitable, and they are the real constituents of a complex [edit: i.e. multi-faceted, not "complex" in the mathematical sense] waveforum (including its initial state). That shape, initially determined by the hammer impact, is modified over time - not only by impedance factors, but also by the influence of wire stiffness on each harmonic's (or partial's) propagation speed. Their sum (at any point in time) determines the shape of the string (at that point in time).

Of course, I'd gladly be proved wrong.

If that is the case, my brain must do FFT analysis before I hear the partials. I am sure I can hear more than one frequency at a time when a piano note is played. If I am not hearing that, then what am I hearing, and, more importantly, how does an aural piano tuner tune?

I think I understand what you are saying, but hammer voicing isn't able to effect one partial vs. the other in terms of loudness. Let me put it a different way: the problem you describe lies not with the hammer, but with something else in the system--it sounds like a string issue to me. Hammer voicing can voice down both the 3rd/4th partials to a level where there is not such difference, but then the overall sound would probably also lose clarity.

Thanks. That was what I wanted to know.

I have assumed that the sound emanating from a piano into the room is similar to the sound emanating from a speaker into the room. The system (strings, bridge, soundboard, case, lid, walls, etc.), due to the interaction of the various components, causes some reinforcement or some cancellation of the various partials (if they exist ), much as the amplifier, speaker crossover, drivers, room interaction causes similar effects on the speaker frequency response.

I would appreciate anyone who thinks that there are an infinite number of sine wave generators in a piano string to show me them. The idea is absurd to me.

Do you hear and use partials when setting the temperament on a piano? If not, how do you tune pianos. (I assume you can tune, though you state you are a tech, not a tuner.)

I tune using beats. Beats are combinatorics, not partials.

In order to have a specific beat rate, you need to have two specific frequencies beating against each other. Given F3/A3 M3 in ET at A4=440Hz, what are the two frequencies that are beating?

Edit: My understanding of combinatorics from ancient high school is that it deals with enumerable elements. This is not the case with beating partials.

Who said anything about an infinite number of sine wave generators and piano strings? BDB, if you think it is an absurd concept, why bring it up and then argue against your own logic? Maybe you should leave the argument part to other people--who are better at it?!?

To isolate an anomaly to a hammer/voicing you could try swapping adjacent hammers. Also, is there a difference with una-corda?

174.6 and 220.0, of course. What else would they be?

Beats occur as the maxima and minima of those two vibrations coincide, alternating with the coinciding of the maxima of one and the minima of the other. Pure combinatorics!

is this a really bad joke?!?