And why is it about 343 ms/s in air?
In: Engineering
sound waves can only propagate through a medium, and the medium through which they travel will affect the speed of the waves. Through gases and liquids, sound waves are longitudinal compression waves; when you hear a sound, you are actually detecting the changes in pressure caused by whatever created the sound. Think of a big speaker; the cone of the speaker is pushing and pulling the column of air in front of it, compressing and relaxing the column at whatever frequency is driving the speaker. Your ear drum feels the changing pressure at the same frequency and you hear the sound. If the molecules this pressure is pushing/pulling are heavier or lighter (really, if the gas is more or less dense), they will be pushed less/more, and the speed of the wave will change.
There’s also another property of substances called a bulk modulus; this is basically how easy it is to compress; the easier it is to compress the easier sound will travel through it. Speed of sound is the square root of this bulk modulus divided by the density. Working that all out for air at 20 degrees C at sea level gives ~343m/s
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