What is sound and how is it different underwater?
Sound is caused when objects vibrate. The vibration of an object creates a pressure wave that can travel through any material. Sound waves (like water waves) can be described in terms of their frequency, wavelength, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit time and is measured in Hertz (Hz) or cycles per second. To the human ear, an increase in frequency is perceived as a higher pitched sound, while a decrease in frequency is perceived as a lower pitched sound. Humans generally hear sound waves whose frequencies are between 20 and 20,000 Hz. Below 20 Hz, sounds are referred to as infrasonic, and above 20,000 Hz as ultrasonic. The frequency of middle “C” on a piano is 246 Hz. Wavelength is the distance between two peaks of a sound wave. It is related to frequency because the lower the frequency of the wave, the longer the wavelength. Amplitude describes the height of the sound pressure wave or the “loudness” of a sound and is often
