Speed of Sound

The speed of sound varies depending on the type of elastic medium it is propogated in.

The speed of sound in dry air at a temperature of 0 degree C is approximately 344 m/sec (1130 ft/sec).

Medium	Speed (ft/sec)	(meters/sec)
air	1130	344
water (salt)	4900	1500
wood (fir)	12500	3800
steel	16600	5050
gypsum board	22300	6800

This difference in speed explains why (for example) one may hear a train coming through the steel rails long before you hear the train via air-conduction.