How Many Types of Sound are There

Introduction

There are three types of sound waves- ultrasonic waves, sonic waves and infrasonic waves. A sound wave is the periodic compression and rarefaction of any elastic medium. Compression is the phenomenon of molecules in the medium being pressed together and resulting in an increase in pressure, whereas rarefaction is the opposite phenomenon where the molecules in the medium are allowed to spread apart resulting in a decrease in pressure. The medium of the sound waves can be either air or water.

Sound waves like other waves have characteristics like their wavelength, frequency, and amplitude. The wavelength and frequency of sound waves can be easily interpreted as their pitch, like high-pitch or low-pitch sounds. The amplitude of a sound wave can be easily interpreted as to how loud a sound is.

Ultrasonic Sound Waves

The term "ultrasonic sound” refers to a sound wave above the frequencies of audible sound, and mainly it includes anything over 20,000 Hz. The frequencies which are used for medical diagnostic ultrasound scans range from 10 MHz and beyond. Sounds that extend from 20-100 kHz are usually used for communication and navigation by dolphins, bats, and some other species. Higher frequencies, ranging from 1-20 MHz, are used for medical ultrasound.

Sonic Waves

The human ear can easily recognize frequencies extending from 20 Hz to 20 kHz. As a result, sonic waves or audible sounds are defined as sound waves with frequencies ranging from 20 Hz to 20 kHz. If the sonic frequency range is present, then the human ear will be sensitive to every minute pressure fluctuation produced in the air. Examples of sonic waves include waves produced by vibrating sitar, guitar, flutes, organ pipes, shehnai, etc.

Infrasonic Waves

Infrasonic waves, vibrational or stress waves in elastic media, have a frequency less than those of sound waves that can be perceived by the human ear—i.e., below 20 hertz. The range of frequencies ranges from geologic vibrations that complete one cycle in 100 seconds or longer. Infrasonic waves include waves that occur in earthquakes, volcanoes, waterfalls, ocean waves, and a variety of atmospheric phenomena like thunder, wind and weather patterns.

How Sound Waves are Created

The sound waves are produced by collisions between objects, because of the human voice, and by the means of devices like speakers. When devices like stereo speakers create a sound wave, it does so by quickly moving their surface membrane inward and outward. The outward motion causes the neighbouring air molecules to be compressed whereas the inward motion causes rarefaction. Altogether, this rapid movement of the speaker's membrane is capable of creating a whole range of sounds, which corresponds to an increase in pressure.

The wavelength of a sound wave refers to the physical length from 1 point of compression to the next. The frequency of a sound wave refers to how quickly the periods of compression pass an observer. The amplitude refers to how compressed the air molecules are and how much energy they carry.

Conclusion

A sound is a form of energy which is produced by vibrations. The surrounding air molecules move when any item vibrates. These molecules collide with the neighbouring molecules, which forces them to vibrate as well, which in turn causes them to collide with other surrounding air molecules. This type of chain reaction movement is known as sound waves which continue indefinitely till the molecules run out of energy. The three types of sound waves include sonic waves, ultrasonic waves and infrasonic waves. The sound waves with frequencies extending from 20 Hz to 20 kHz are referred to as the audible range, and these waves are called sonic waves.

An ultrasonic wave is a type of longitudinal wave with a frequency greater than sonic waves i.e. above 20 kHz. An infrasonic wave is a type of longitudinal elastic wave with a frequency less than the audible range, i.e. 20 Hz. It is usually produced by a huge source such as elephants using infrasonic sound waves to interact with their herd hundreds of km away.