Speed of sound waves - SS3 Physics Lesson Note

The speed of sound waves varies depending on the medium through which they are travelling. This is because of the fact that there exist three (3) states of matter (solid, liquid and gas) which sound waves can propagate through. In general, sound waves travel faster through denser mediums, such as solids, than through less dense mediums, such as gases.

At sea level and at a temperature of 20 degrees Celsius (68 degrees Fahrenheit), the speed of sound in dry air is approximately 343 meters per second (1,125 feet per second), or about 1,235 kilometres per hour (767 miles per hour). This value can vary depending on factors such as temperature, humidity, and atmospheric pressure.

The speed of sound is faster in liquids and solids than in gases due to the increased density of these materials. For example, in water at 20 degrees Celsius, the speed of sound is approximately 1,484 meters per second (4,870 feet per second), while in steel it can be as high as 5,960 meters per second (19,550 feet per second).

Example: A soundwave travelling through dry air has a frequency of 58Hz, what is its wavelength?

Solution: Recall the speed of sound in dry air is 343 M/s

Frequency of the waves is 58Hz

\(\lambda\ = \ V \div \ f\), substituting,

λ = \(343\ \div \ 58\), λ = 5.91 meters

The speed of sound waves is an important factor in many fields, including acoustics, engineering, and physics. It is also a crucial parameter for understanding the behavior of seismic waves in the earth's crust, and for designing and testing supersonic aircraft and rockets.