Final answer:
A sound wave is characterized by alternating high-pressure areas (compressions) and low-pressure areas (rarefactions) caused by a vibrating source, which can be represented graphically using sine functions of pressure versus distance.
Step-by-step explanation:
The pattern of changes in air pressure that constitutes a sound wave involves alternating regions of high pressure (compressions) and low pressure (rarefactions). When a vibrating source like a speaker cone or a string moves, it creates compressions by pushing air molecules together and rarefactions by pulling them apart. This results in a longitudinal wave pattern of pressure changes propagating through the air. Sound waves, therefore, exhibit a sine function pressure model when graphed as gauge pressure versus distance, with crests representing compressions and troughs representing rarefactions.
Increasing the frequency of the source's vibrations increases the pitch of the sound heard, while the amplitude of the vibrations determines the volume. The intensity of a sound wave is proportional to the square of the pressure change and inversely proportional to the density and speed of the medium. When a sound wave travels from one medium to another, the wave's speed may change; however, its frequency remains constant, leading to a change in wavelength.