Speed of sound wave

Professional Definition

The speed of sound (denoted by the symbol c) is the speed at which a mechanical disturbance travels through an elastic medium. It is the distance that the wave front travels in a unit of time.

This value is strictly dependent on the physical properties of the medium through which the wave travels, specifically its stiffness (elastic modulus) and density. For air at a temperature of 20°C (normal conditions), the speed of sound is about 343 m/s (1235 km/h). It is important to remember that this speed increases with rising gas temperature, but changes drastically with changes in the state of the medium.

Acoustics in Simple Words

Imagine a sound wave as a relay passing a message, and the particles of the medium (e.g., air) as runners. For sound to travel from point A to B, one particle must strike another, transferring its energy.

In gases (like air), the particles are spaced apart – the “runners” are far away, so passing the baton takes a relatively long time. In solid bodies, such as steel or concrete, particles are packed very tightly and connected by rigid bonds. This works like a Newton's cradle (a row of hanging balls) – a strike on the first ball quickly transfers energy to the end of the row. Therefore, sound travels through steel at a speed of over 5000 m/s – more than 15 times faster than in air. This explains the old trick from Westerns: by putting an ear to railroad tracks, you can hear an approaching train much sooner than you would hear it in the air.

Summary

The speed of sound is a parameter that defines how quickly sound energy is transported through a given material. It is lowest in gases, average in liquids, and highest in solids. Understanding this phenomenon is crucial when designing sound insulation and public address systems, where sound delays can affect the clarity of the message.