Del, Thanks a bunch for the modulus and density info. I looked for it a whole back and couldn't find it. Can you tell me what type of wood these numbers are for? I started to do a simple finite element model of a soundboard with a 3 string unison to look at how much the board stiffness changes the response of the strings... I need the modulus of both spruce and maple to do a more accurate job, but anything you have is better than nothing. doug richards San Jose, CA > -----Original Message----- > From: Delwin D Fandrich [SMTP:pianobuilders@olynet.com] > Sent: Thursday, May 28, 1998 1:22 PM > To: pianotech@ptg.org > Subject: Re: Sound in Feet per Second. > ... > THE SPEED OF SOUND (SOS) THROUGH WOOD: > The speed of sound through wood is independent of species. > -- It VARIES DIRECTLY - with the square root of the modulus of > elasticity (MOE). > (Transverse (radial) MOE can be 1/20 of the longitudinal value, > hence, the > speed of sound across grain is 1/3 to 1/5 the longitudinal value.) > -- It VARIES INVERSELY - with the square root of the density of the > material. > -- It VARIES WITH - grain direction, or angle. > -- It VARIES INVERSELY - with wood temperature and with moisture > content (MC). > Both temperature and MC affect MOE. > -- It VARIES INVERSELY - with both frequency and with the amplitude of > vibration. > > In the piano soundboard the speed of sound in, or through, wood is only > important because > of its direct effect on wave velocity, hence wave impedance. It is not > important in and of > itself. > > A piece of wood with a longitudinal modulus of elasticity (MOE) of > 1,800,000 psi and a > density of 30 lb/ft3 would have a speed of sound in the longitudinal > direction of about > 150,000 in/sec. In the transverse direction, its MOE would be about > 100,000 psi and the > speed of sound would be approximately 35,000 in/sec. > > Regards, > > Del > >
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