Hi Don So your take on this is resultant tones rather then coincidents ? Thats the direction I am leaning as well. I did a few tests with my handy dandy pitch fork and pocket tunelab today. Basically trying out what kind of inharmonicity readings I get on the fork when I place it on different types of objects. I found that anything that conducted the fork really well resulted in no overtone until around the 6th. Sometimes the 5th would pop up depending on what I grounded the tuning fork on. Putting it directly on the mic I dont get anything until the 10th partial. All of which is in keeping with the descriptions I've found on the net and in a couple books I have. Interestingly enough... when the fork was placed on sidegrain of a table the forks sound was quite reduced, and I got very high readings (50-80) on a second partial. When I placed it on end grain I got low but significant (10-20) Both readings showed 0.0 offset at 880. This is in keeping with a couple experiments I found on the net entitled "Forceing a tuning fork to have overtones" Seems like it has more to do with the what you place the tuning fork on. I tried grounding it on a metal note stand... really loud result and no 2nd partial. Glass was the same even tho the overall loudness was much quiter. All this points me in the direction that the apparent overtone some folks are reporting is being generated by the thing the fork is grounded on .... and not the fork itself. As to the wave file I posted... I thought I might show you a couple other perspectives. The wave was a one second sample. The two pics below show a 1:4 resolution and a 1:10 resolution. Note the presence of another beat. The inside peak you see in the 1:10 resolution happens exactly 7 times in the full one second sample. Thats the resultant beat. http://www.pianostemmer.no/images/fourtimes.jpg http://www.pianostemmer.no/images/tentimes.jpg Now look at the same 1:10 resolution for a mix of 440 and 447 which is analogous to what happens with coincidents. Interesting eh ? http://www.pianostemmer.no/images/tenxcoincident.jpg Seems to me like we are dealing with beats that are origionating in absence of simple coincident partials. Cheers RicB Hi Ric, You are right--it doesn't "add up" at all. It subtracts. Look at one second of the sin wave scan. You will see the 7 "peaks" from the secondary resultant easily visible. At 10:46 AM 1/12/2006 +0100, you wrote: >Kent: > >The sine waves that I combined together to make the wave file I posted >show no measureable overtones using Tunelabs Inharmonicity tool. Neither >could Cybertuner pick anything up. Now the phase display that Tunelab >has showed a very intermittent response at around 880 for the 440 >signal. This response faded in and out and its frequency wavered quite >a bit. I doubt that this is an overtone per se. I fail to see how these >non existing coincidents can account for the beat rate in the wave file. >And so I question whether or not it is there. This echos Ed's and others >ponderments and its a fair question. And I dont see that simple >coincident partials theory provides an answer to it. > >Every link I find that describes tuning forks describes them as >instruments that have (for all practical purposes) no overtones. Such >as the below. Several sights which describe experiments like the one you >did with your cybertuner attribute (sometimes) presence of very weak >overtones that are not accounted for by the design of the tuning fork to >sympathetic vibration from surrounding material... such as what ever you >grounded your tuning fork on. John Walker tuning forks make a real big >point out of emphazising the <<overtone free>> characteristic of their >tuning forks in all their advertising. One other point. The duration >and strength of your <<overtone>> is not sufficient to account for the >long duration and intensity of the beating between the fork and the non >coincident F3. > >I say something doesnt add up. > >Cheers >Ric Regards, Don Rose, B.Mus., A.M.U.S., A.MUS., R.P.T. Non calor sed umor est qui nobis incommodat
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