source file: mills2.txt Date: Thu, 27 Feb 1997 02:53:33 -0800 Subject: Re: Sympathetic Vibrations From: Matt Nathan Lydia Ayers wrote: > > Paul Hahn wrote: > > >Yes, but tubes present orders of magnitude more surface area to be acted > >upon by sound pressure than strings do. > > Yes, they do have more surface area, and they could even be seaid to > contain their own resonators, since they are hollow. But, even so, > it is the air that carries the vibrations which stimulatie the > sympathetic vibrations, not a sounding board connected to the > original stimulauus and not cables or anything. else. I think what Paul Hahn means is that the greater surface area allows the vibrations of the air to be transferred into the body of the instrument more easily. I would add that it it also allows the reverse, so the greater the vibrating surface area, the louder the instrument is and the more sensitive to external sounds it is, so we hear tubular bells resonate to coughs because of their surface area coming and going, but we don't hear lone strings (without a soundbox) resonate because of their surface area coming and going. Of course there are other factors too. A painting has a lot of surface area but is not either very stiff or very tense (as a drum head would be) and absorbs the air vibrations, changing them into heat via internal friction in the canvas. Since writing the above, I've read further in the thread. I will add that a sound box (like the body of a violin) is designed not to have particular resonances, or at least to have its resonances spread out into wide bands. That's why you don't hear the violin body responding to and sustaining particular notes when you sing while muting the strings. The strings are designed to have strong resonance peaks which is why certain notes are sustained when you sing while the strings left free to vibrate. A sound box is also designed to be in good contact with the vibrating element (violin string) so that vibration can be conducted from the element to the sound box and then to the air for us to hear. Now, I know of no way to allow sound conduction in one direction and not the other. Sound must conduct mechanically from the sound box to the string just as easily as from the string to the sound box. Also sound must conduct as easily from the air into the sound box as it does from the sound box into the air. The sound box and string together then make a single vibrating system, which is in good contact with the air. It has the dual advantages of musically usable high-peak resonances (the centers of these resonances are even adjustable by stopping the string to different lengths!) and good body-to-air contact provided by the large surface area of the sound box. Since sound is conducted equally well in both directions between string and body, and equally well in both directions between air and body, it makes sense to me that when you sing, the air vibrations are picked up only slightly by the string's small contact with the air and more greatly by the body which then conducts the vibration to the strings, but that the strings, though having poor direct contact with the air, will determine which notes the system as a whole resonates best to. Going back to the hanging chimes, each tubular bell is a single system which has both large surface area and definitive peak resonances (unlike a violin body). Now, what do we tune these to? :) Matt Nathan Received: from ns.ezh.nl [137.174.112.59] by vbv40.ezh.nl with SMTP-OpenVMS via TCP/IP; Thu, 27 Feb 1997 12:42 +0100 Received: by ns.ezh.nl; (5.65v3.2/1.3/10May95) id AA01758; Thu, 27 Feb 1997 12:42:16 +0100 Received: from ella.mills.edu by ns (smtpxd); id XA01689 Received: from by ella.mills.edu via SMTP (940816.SGI.8.6.9/930416.SGI) id DAA29154; Thu, 27 Feb 1997 03:40:04 -0800 Date: Thu, 27 Feb 1997 03:40:04 -0800 Message-Id: <199702270634_MC2-11D0-A111@compuserve.com> Errors-To: madole@mills.edu Reply-To: tuning@ella.mills.edu Originator: tuning@eartha.mills.edu Sender: tuning@ella.mills.edu