We explain what sound is, its characteristics and how it propagates. Also, what are its properties and what is musical sound.
What is sound?
When we talk about sound, we refer to the propagation of mechanical waves caused by the vibration of a body through a fluid or an elastic medium. These waves may or may not be perceived by living beings, depending on their frequency.
There are sounds audible to the human ear and others that are only perceived by certain species of animals. These are acoustic waves produced by the oscillation of air pressure, which are perceived by the ear and transmitted to the brain to be interpreted. In the case of humans, this process is essential for spoken communication.
Sound can also propagate in other elements and substances, liquids, solids or gases, but often undergoing certain modifications. It is about a transport of energy without transport of matter and, unlike electromagnetic waves of light or radiation, it cannot propagate in a vacuum.
Sound is studied by acoustics, a branch of physics and engineering. Also It is of great interest for phonetics branch of linguistics specialized in the oral communication of human beings in their different languages.
See also: Color
Sound characteristics
Sound is produced when a body vibrates, and transmits these vibrations to the surrounding medium in the form of sound waves. These move expansively, at an average speed (in air) of 331.5 m/s, and can reverberate (“bounce”) on different types of surfaces, achieving different echo or distortion effects which often magnify their power (as in soundboards or speakers).
Sound has the following physical characteristics:
- Frequency (F). It is the number of complete vibrations per second that the sound source makes and that is transmitted in waves. A sound audible to humans will have a frequency between 20 and 20,000 Hz. Above that range it will be an ultrasound perceptible, at most, to some animals.
- Amplitude It is the intensity (acoustic power), which we usually call “volume.” Amplitude is related to the amount of energy transmitted by sound waves.
- Wavelength (λ). It is the distance that a wave travels in one oscillation period, or in other words, the distance between two consecutive maximums of the oscillation.
- Acoustic power (W). It is the amount of energy emitted by waves per unit of time. It is measured in watts and depends directly on the wave amplitude.
- Frequency spectrum It is the distribution of amplitudes, or acoustic energy, for each frequency of the various waves that make up sound.
How does sound propagate?
Sound propagates in liquids, solids and gases, but it does so more quickly in the first two. This is because the compressibility and density of the matter have effects on the transmission of waves: the lower the density or the greater the compressibility of the medium, the lower the speed of sound transmission. Temperature can also influence the matter.
Thus, the propagation of sound cannot occur if there is no material medium whose molecules can vibrate. For this reason, an explosion in outer space could not be perceived auditorily, while the sound of a train arriving, for example, reaches us thanks to the sound wave being transmitted through the air.
Sound properties
Broadly speaking, sound has four main properties:
- Height or tone According to their frequency, sounds are classified as high (high frequency), medium (medium frequency) and low (low frequency). Frequency is what distinguishes musical notes from each other.
- Duration It is the time during which the vibrations produced by a sound are maintained.
- Intensity It is the acoustic power (amount of energy per unit of time) per unit of air, and is measured in decibels (db). A sound is audible to humans above 0 db, and produces pain above 130 db.
- Ring It is a quality that allows us to distinguish two sounds of equal frequency and intensity emitted by different sources. As the frequency of a sound, in general, is not unique but there is a fundamental one and others of lower intensity, the timbre is related to the intensities and varieties of those other frequencies that accompany the fundamental one.
musical sound
Music is the rhythmic and ordered set of sounds generally those coming from musical instruments and the human voice (singing). The distinction between music and noise is of cultural origin and has to do with considerations of harmony and beauty of the time.
