An acoustic wave is an oscillation of pressure that travels through a solid, liquid, or gas in a wave pattern. It transmits sound by vibrating organs in the ear that produce the sensation of hearing. Acoustic waves, or sound waves, are defined by three characteristics: wavelength, frequency, and amplitude.

The wavelength is the distance from the top of one wave’s crest to the next. The frequency of a sound wave is the number of waves that pass a point each second. Sound waves with higher frequencies have higher pitches than sound waves with lower frequencies. Amplitude is the measure of energy in a sound wave and affects volume. The greater the amplitude of an acoustic wave, the louder the sound.

An acoustic wave is what makes humans and other animals able to hear. A person’s ear perceives the vibrations of an acoustic wave and interprets it as sound. The outer ear, the visible part, is shaped like a funnel that collects sound waves and sends them into the ear canal where they hit the ear drum, which is a tightly stretched piece of skin that vibrates in time with the wave. The ear drum starts a chain reaction and sends the vibration through three little bones in the middle ear that amplify sound. Those bones are called the hammer, the anvil, and the stirrup.

From here, the vibrations of the sound wave are turned into electrical impulses that the brain can interpret. The stirrup bone presses against the fluid-filled cochlea, or hearing organ, in time to the acoustic wave. The fluid inside the cochlea moves because of the stirrup bone’s pressure, and in turn, moves a hair-cell-lined membrane buried within the fluid.

The hair cells move according to the pattern of the acoustic wave, sending signals to nerve cells that carry their interpretation of the wave to the brain. The brain interprets the acoustic wave as sound and as a result, we hear. The human brain likes patterns, and it is interesting to note that it interprets regular sound wave patterns as pleasant and irregular wave patterns as nothing more than unpleasant noise.