Introduction to sound waves - SS3 Physics Lesson Note

Sound waves classify as longitudinal mechanical waves that can be heard by the human ear. Recall that with longitudinal waves, particles in the medium (such as air, water, or solids) move parallel to the direction of the wave's propagation.

Sound waves are produced by vibrating objects, such as the vocal cords of a person or the strings of a guitar. These vibrations cause the molecules in the surrounding medium to vibrate as well, which creates a disturbance that travels through the medium as a sound wave.

Sound waves have several characteristics, including amplitude, frequency, and wavelength. The amplitude of a sound wave determines its loudness, while the frequency determines its pitch. The wavelength of a sound wave depends on the speed of sound in the medium, which in turn depends on the properties of the medium such as its density and temperature.

Human ears are sensitive to sound waves with frequencies between about 20 Hz and 20,000 Hz, although this range can vary depending on factors such as age and exposure to loud noise. Sounds with frequencies below this range are called infrasound, while sounds with frequencies above this range are called ultrasound.

Sound waves have many practical applications, including in music, communication, and medical imaging. Understanding the behaviour and properties of sound waves is therefore important in many fields of science and engineering.