Reason for very low speed of sound in rubber I just came by a table in the Class 11 Physics NCERT textbook, listing speeds of sound in different media.
Vulcanised rubber has an unusually low speed of sound $54\ \mathrm{m}/\mathrm{s}$ as compared to the other solids, e.g $6000\ \mathrm{m}/\mathrm{s}$ for granite and $3560\ \mathrm{m}/\mathrm{s}$ for copper. This is intriguing. 
Speed of sound in general is:
$$v = \sqrt{ \frac{\text{Elastic properties}}{\text{Inertial properties}}} $$
Elastic property in this case should be bulk modulus (or Youngs or shear, I am confused) which should be low to support the observation. Is this because rubber is a polymer? 
I checked the internet for speed of sound in other polymers but found no satisfactory results. 
I would really like to know the reason for this anomaly.
 A: The Young's modulus of rubber is about 4×10^6 and it's density is 1200 kg/m³ if you plug in the values in v=√(Y/μ) you get v=57.7m/s. According to me the probable cause of the anomaly should be abnormally high density of rubber due to vulcanization and abnormally low modulus of elasticity
A: Remember that sound is a vibration of kinetic energy passed from molecule to molecule.
At the particle level, a rigid material is defined by atoms and/or molecules with strong forces of attraction for each other. You must have learnt that the particles vibrate about their mean positions like springs. They quickly return to their original position. 
Particles that return to their mean position quickly are ready to move again more quickly, and thus they can vibrate at higher speeds. Therefore, sound can travel faster through steel (which has high elastic properties) than it can through rubber (which has lower elastic properties). Also, rubber has a very low modulus of elasticity, unlike the other materials you mentioned.
