modulus of the liquid r is its density. For water, at a temperature of 20oC, B = 2.05 x 109Nm-2and
r = 1000 kmg-3
The velocity of sound in water was determined by Daniel Colladon and Jacob Sturm in the lake of Geneva in 1827. Two observers were stationed on boats 9 miles apart, a large bell immersed in water being suspended from one boat, while the other had an ear trumpet with an elastic membrane stretched across it. The hammer of the bell was connected to a lever which could ignite some amount of gun powder when the hammer struck the bell. The observer in the second boat listened to the sound through a tube connected to the trumpet and timed the interval between seeing the gunpowder flash and hearing the sound. The experiment was carried out at night, so that the flash was more easily visible. They obtained the velocity of sound as 1435ms-1.
When sound passes through a thin rod, the velocity is given by the formula
Where l is the
Young's modulus of the material of the rod and r
is its density. For steel,
When sound travels through a solid block, both the bulk modulus (g), and the rigidity modulus (n) are involved. Then, the velocity of
sound is given by the formula
The velocity of sound in iron was determined by two French investigators by striking one end of a long series of connected iron pipes with a hammer and measuring the time interval between the two sounds heard at the other end, the one transmitted by the solid and the other by the air in the pipe. With the knowledge of the velocity of sound in air, its velocity in the solid was calculated.
