How do you characterize sound? Intensity or Loudness
The amplitude of a wave depends on the amount of energy that it carries. A high amplitude wave carries a large amount of energy where as low amplitude wave carries a small amount of energy.
The average amount of energy passing through a unit area per unit of time in a specified direction is called the intensity of the wave.
When the amplitude of the sound wave increases, the intensity of the sound also increases. Sounds with higher intensities are become louder.
Relative sound intensities are often given in units named decibels (dB). The Bel is the primary unit and a decibel is 1/10th of a Bel.
The Bel is a ratio of the pressure of a sound to a reference pressure. The reference pressure in air is 20 microPascals (µPa). The reference pressure in water is 1 microPascal (1 µPa).
Intensity: The average amount of sound power (sound energy per unit time) that transmitted through a unit area in a particular direction.
The unit of intensity is watts per square meter.
The magnitude of the intensity of sound simplicity referred as the intensity, without specifying the direction in which the sound is traveling.
Frequency or Pitch : Frequency is the rate of repetition of a regular event. A wave has a repeating pattern. One such repetition is known as a wave cycle. When talking about sound, frequency means the number of cycles of sound in a second.
The unit used to measure frequency is named Hertz, which is defined to be the number of cycles in one second. (This unit is named after Heinrich Hertz, a famous 19th century physicist).
Wavelength: The length of one wave cycle is the wavelength. The wavelength can be measured as the distance from the top of one wave to the top of the next wave or from the bottom of one wave to the bottom of the next.
You can also think of the wavelength as the distance that a sound wave travels in one cycle. Wavelength is related to the speed at which sound travels.
You can calculate the wavelength of sound in seawater by dividing the speed of sound by the frequency of the sound:
Wavelength = Speed of sound / Frequency of sound
Speed of Sound: Sound moves about 1500 meters per second in seawater. Sound moves much more slowly in air, at about 340 meters per second.
Sound speed is affected by the oceanographic variables of temperature, salinity, and pressure. Here we are referring to the ocean pressure due to the weight of the overlying water (equilibrium pressure), not to the pressure associated with a sound wave, which is much, much smaller.
Reflections of sound : Sound bounces off hard surfaces. It echoes from the walls of underwater canyons. Just as a mirror reflects light, hard surfaces such as canyon walls reflect sound.
The amount of sound that is reflected and transmitted depends on the properties of the two media and on the angle of incidence.
Refraction of sound : Sound is refracted just as light is. Refraction occurs not only when light moves from water to air, but whenever the speed of light changes.
Similarly, a sound wave traveling through the ocean is bent whenever it encounters changes in the speed of sound. Since sound speed changes with changes in temperature, salinity, and pressure, a sound wave will refract as it moves through the ocean.
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