The Speed of Sound

What is the speed of sound?

The speed of sound is the distance travelled by a sound wave as it propagates through an elastic medium.

Calculation:  Speed = distance / time

What speed does sound travel thru the air?

The speed of sound varies depending on the temperature of the air through which the sound moves.  The speed of sound also varies depending on the type of gas through which the sound moves (pure oxygen, carbon dioxide, etc.)

In air at room temperature the speed of sound travels at 346 meters per second.

At freezing temperatures the air molecules vibrate slower and sound travels at 331.5 meters per second.

On earth and at sea level with an air temperature of 15 degrees Celsius the speed of sound is 1225 km/h or 761.2 mph.  The speed to break the sound barrier decreases higher in the atmosphere, where temperatures are colder

The Temperature and the speed of sound can be calculated as follows:

Convert the air temperature in °C or °F, first to kelvins.

Add 1 to the temperature in kelvins and take the square root.

Multiply the result from Step 2 by 331.3.

The answer is the speed of sound in air in m/s.

What is Mach 1?

It is a number that is a ratio of the speed of a body (car/aircraft) to the speed of sound in an undisturbed medium through which the body is travelling.  The numbers came into use in 1929 and are named after Ernst Mach (1838-1916).

Calculation: Ratio = Object Speed / Speed of Sound = Mach Number.

What happens when you break Mach 1?

Anything exceeding the speed of sound creates a “sonic boom”.  An airplane, bullet etc.   

Nasa reached Mach 10 speed in 2004 when it launched X-43-A the first air-breathing hypersonic vehicle into the atmosphere (7000mph @ approximately 110 000 feet)

Why is the speed of sound maximum in solids?

The molecules are closer together in a solid medium which allows the sound waves to travel more quickly through it.