Hi Joe, Yep, I don't think I'm dealing with sympathetic vibrations. Because it happens with just about all of the intervals within the range I am hearing it. A particular sympathetic buzz would only only respond to it's harmonic relatives - right? Plus I tried the test you suggested - with no response from the culprit. Also the tone/buzz I am hearing is at the frequency you described (i.e. the difference between the fundamental frequencies) Problem is the tone/buzz is not pleasant or supportive to the sound. It is sort of hoarse and spurious with an slow oscillation dying out quickly. In some cases it can be quite loud - actually interfering with the sound of the chord or interval. I'm pretty sure I don't hear it much on other pianos - although I don't have one to run to at the moment. This seems like something that would be quite familiar to a lot of tuners if it was any kind of common issue ... I'm starting to suspect my own ears, or does the piano have some kind of strange ailment??? Thanks Jeff On Feb 16, 2011, at 11:36 PM, Joe DeFazio wrote: >> From: Jeff Atkisson <jeffkiss at sonic.net> >> Date: February 16, 2011 12:42:22 PM EST >> >> Hi, you all don't really know me - but maybe you have a quick answer >> for me. >> >> It's a Stenway M. >> Octave 6 and 7 (mainly) >> Play a fourth or a fifth say from E6. >> Strange (to me) "buzzing' or humming sound at a lower harmonic (i.e. >> at approximately E5 when playing E6-B6). >> Piano is in tune. (does it with single strings) >> Only does it it with intervals (not single notes). >> Lasts for around a second or two ... >> Does it with most of the intervals played in this range (not in high >> treble or below about C6). >> It muddies the sound of chords and intervals there. >> >> It seems like its the board but I can't seem to stop it by pressing >> on ribs - although I haven't done extensive searching in this regard. >> >> You all know what this is? >> >> Please don't tell be its my ears or my imagination ... >> >> pretty sure I could catch it with a mic if I could post the sound >> clip. >> >> Thanks >> >> Jeff > Hi Jeff, > > You are probably hearing a difference tone. Sum and difference tones > are tones that are produced at the sum and difference between the > frequencies of two simultaneously sounding tones. Of the two, only > the difference tone is often heard in pianos, and it is often most > audible in the mid to upper treble with perfect intervals, somewhat as > you describe. > > As an example, let's for a moment forget inharmonicity just to make > the math easier (think of an organ instead of a piano if that > simplification offends you). The note A4 is at 440, with partials at > 880 (A5), 1320 (E6), 1760 (A6), and so on, as you surely know. Now, > if you play E6 (1320) and A6 (1760) together, you will (or may, > depending on the strength of the fundamentals of those two notes, and > on your aural perceptiveness, of course) hear a difference tone at: > > 1760 - 1320 = 440, or A4. That's a difference tone. It is real > (measurable and reproducible); it is not a psychoacoustic effect. > > Now, it is entirely possible that in your particular case the > difference tone itself is, by coincidence (I guess that's sort of an > unintentional bad pun), exciting a sympathetic buzz in some other > object in the room or in the piano, but that would be unlikely. You > can rule that out by playing the note that you hear as a difference > tone (in the example I gave, you would play the note A4). If that > note does not elicit a sympathetic buzz, neither will the difference > tone, in which case, the low humming sound that you are hearing is the > difference tone itself. > > You may be interested to know that a next generation of highly > directional speakers based on difference tones is in the works. Since > high sounds are highly directional, a tweeter produces two sounds > above the range of human hearing that create a difference tone within > the range of human hearing. This difference tone may even be a low > note, but it will be highly directional (you will only hear it if the > tweeter is pointed right at you), even though low sounds are usually > non-directional (thats why you can put your subwoofer almost anywhere, > and why you hear the subwoofer in some hearing-damaged kid's trunk > even when you can't hear the rest of his "music," (fortunately, most > likely)). > > Joe DeFazio > Pittsburgh -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: text/enriched Size: 4510 bytes Desc: not available URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110217/9e19920a/attachment.bin>
This PTG archive page provided courtesy of Moy Piano Service, LLC