differencial tone annoying ( 3ds)

[Olek]

Hello,

A customer of mine, acoustician an accordion player, was called to check a room where someone have a kawai baby grand, that is generating "differential tones" audibly, and all along a series of min 3ds in the 5th 6th octaves.

I could not witness the effect myself but she could measure the frequency , an I hope I will have a recording, joining the piano owner.. (possibly a sound professional, working for our Nat radio)

A tech was there and checked damper seating so all is well there , I was said.
Sometime a part of the backscale is ringing but it will not make a chromatic scale, only a few notes, generally only one or 2

The acoustical effect is well known the difference between 2 frequencies for instance G#5 B5 832-990 Hz are generating a 990-832 = 158Hz, measured on the piano 163 Hz ((E 3). The min 3ds in the neighborhood are also generating frequencies .

My customer tol me this effect is easy to perceive at the accordion. I Personally I never noticed that on a piano.

SO looking for a cause (plate highly under stress, making the whole structure more reactive) an effect of the spherical iron used with vacuum molded plates and that do not damp vibrations as well as grey lamellar iron, anything !!

ANy idea welcome, I will keep you posted with the model of the piano - hopefully a recording - it must be very recent and will be changed in december.
My customer checked the room and those are not room induced effects, as standing waves she is sure.

Best regards

[Olek]

What I notice is that a 5th have the lower tone stronger due to a differential tone that happens one octave below, but I was never really attentive to other combinations.

AT the organ those tones are clearly audible, listen to the samples here if you wish :

http://organ-au-logis.pagesperso-orange ... ltante.htm

Very possibly there is on line a tone generator allowing to experiment that effect (additive or subtractive) I have seen one page with that (In english ,also with phase orientation) but cannot find it at the moment, if someone know about that, please forward the link.


The pianist is sound engineer, and developped some sensitivity to that effect. He tested on other pianos, his is a RX6 , not new but in a new room.

He heard the differential tone on some other pianos, a Fazioli for instance.

Now I am unsure min 3ds are fautive, more M3 as he said. I will know more tonight.



Regards

[vernon]

not understand any of this

[Colin Nicholson]

very confusing dot com

[Olek]

Sorry you did not get it. Those are combination tones too present

Easy to experiment with one of the double tone generators available on the net

For instance on that one : http://digilander.libero.it/i2phd/tcube/tcube.html (with spectra graph)

or http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3829 just tones

use the frequencies for a min third, a maj third, a 5th, an see/hear the "differential tone"

ex 990 832 hz but 400 600 also rises a 200 Hz frequency, for instance. (hence the strong fundamental of the "pure 5th")

That acoustical effect is not much present in pianos (for whatever reason , I don't really know) so we never hear about. The case I wrote about is a piano RX6 (not a small grand) that have those tones too present, and we are looking for a cause .

http://en.wikipedia.org/wiki/Combination_tone

Thanks

[rxd]

I have been sensitive to resultants ever since I was given some old organ pipes as a teenager and used two of them attached to an old piece of pipe that have an interval and it's resultant making three notes. The resultant was just as loud as the other two notes and my trick was to sound the pipes and ask people which two pipes were sounding the actual notes.

Resultants are useful for keeping wind instruments in tune on the fly in performance they are readily aidible in flute duets but are of no use for tuning equal temperament on a keyboard. They can be useful for betraying faulty unisons, though when six strings are sounding that form a M3 or a 5th. Also other intervals burtjose two are some of the ones I test most the way up the treble.
Beginning string players also use them for initial tuning of open strings and for the tuning of double stopped notes when there is not much else going on.

Yes, some pianos sound them more than others. I can understand a sound engineer hearing and latching on to them more than most because they are always alert for hums and other lower frequency noises in the electronics and become as sensitised to them as I did, if not more.

As I have often said in other forums, everybody hears very differently and pick up on the most abstruse phenomena that almost everybody else does not hear.

This phenomenon is definitely there to stay. It is an unavoidable part of the sound and the room may indeed by exacerbating it. A recording engineer must have been in situations that include resultants in the sound but, like most of us, never noticed it. Only when it is made obvious does it become am issue.

It's like the after ring on all upright pianos, old and new. Nobody notices it but when they do hear it in their own piano, particularly if it's a new one. I once as a large store head tech. took a lady to her church to have her listen to all the uprights there that she had heard from being a little girl. Sure enough, they all did it and she had never noticed. that trip prevented the needless return of a brand new piano.

It is just one more thing to ignore. That's easy for me and you to say but try saying it to an obsessive person.

[cassidybole]

I wish you can find a solution to your problem.

Hello,

A customer of mine, acoustician an accordion player, was called to check a room where someone have a kawai baby grand, that is generating "differential tones" audibly, and all along a series of min 3ds in the 5th 6th octaves.

I could not witness the effect myself but she could measure the frequency , an I hope I will have a recording, joining the piano owner.. (possibly a sound professional, working for our Nat radio)

A tech was there and checked damper seating so all is well there , I was said.
Sometime a part of the backscale is ringing but it will not make a chromatic scale, only a few notes, generally only one or 2

The acoustical effect is well known the difference between 2 frequencies for instance G#5 B5 832-990 Hz are generating a 990-832 = 158Hz, measured on the piano 163 Hz ((E 3). The min 3ds in the neighborhood are also generating frequencies .

My customer tol me this effect is easy to perceive at the accordion. I Personally I never noticed that on a piano.

SO looking for a cause (plate highly under stress, making the whole structure more reactive) an effect of the spherical iron used with vacuum molded plates and that do not damp vibrations as well as grey lamellar iron, anything !!

ANy idea welcome, I will keep you posted with the model of the piano - hopefully a recording - it must be very recent and will be changed in december.
My customer checked the room and those are not room induced effects, as standing waves she is sure.

Best regards