A sound wave is a series of alternating compressions and rarefactions. Sound waves are longitudinal waves. Sound is a vibration propagated as an acoustic wave through a transmission medium such as a gas, liquid or solid.
How are sounds produced?
Vibrating objects make sound by first pressing air molecules together and then letting them thin out. When objects vibrate, they push on the air molecules nearest them, setting them in motion. These molecules in turn push on the others around them. Since the medium is elastic, a series of compressions (air molecules close together/high pressure) and rarefactions (air molecules spread out/low pressure) is produced.
Credits: Let’s Talk Science
The molecules return to their original position once the energy moves on. Sound travels the fastest through solids and the slowest through gases. This is because the particles in a solid are closer together, making it easier for vibrations to transfer between neighbouring particles.
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Pitch
The pitch of a sound depends on the FREQUENCY. Rapidly vibrating objects produce sound of high frequency (and high pitch), while slowly vibrating objects produce sound of low frequency (and low pitch). The human hearing range is approximately from $20\ Hz\ to\ 20\ kHz$.
Credits: Labster Theory
Loudness
The loudness of a sound depends on the AMPLITUDE of the vibrating object producing it - the greater the amplitude of the vibrator the louder the sound. This is usually measured in $decibels\ (dB)$.
Measuring the speed of sound
The speed of sound in dry air at $20\degree C$ is approximately $343\ ms^{-1}$.
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