We explain what sound is, its characteristics and how it spreads. Also, what are its properties and what is musical sound.

Sound are the waves caused by the vibration of a body through a medium.

What is sound

When we speak of 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 your frequency.

There are sounds audible by the human ear and others that are only perceived by certain species of animals. These are acoustic waves produced by the oscillation of the pressure of the air, which are perceived by the ear and transmitted to the brain to be interpreted. In the case of human being, this process is essential for the communication spoken.

Sound can also spread to other elements and substances, liquids, solid or fizzy, but often undergoing certain modifications. It is a transport of energy without transport of matter and, contrary to the waves electromagnetic light or radiation, it cannot propagate in a vacuum.

Sound is studied by acoustics, a branch of the physical and engineering. It is also of great interest to the phonetics, branch of linguistics specialized in the oral communication of human beings in their different languages.

Sound characteristics

Sound can bounce off different surfaces, achieving echo or distortion effects.

Sound is produced when a body vibrates, and transmits these vibrations to the surrounding environment in the form of sound waves. These move expansively, at an average speed (in air) of 331.5 m / s, and can reverberate (“bounce”) off different types of surfaces, achieving different echo or distortion effects, often magnifying their effect. 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 the waves. A sound audible by humans will have a frequency between 20 and 20,000 Hz. Above that range it will be an ultrasound audible, at most, by 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 a period of oscillation, or in other words, the distance between two consecutive maxima of the oscillation.
  • Acoustic power (W). It is the amount of energy emitted by the 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 the sound.

How sound travels?

Sound propagates in liquids, solids and gases, but it does so more quickly in the first two. This is because compressibility and density of matter have effects on the transmission of waves: the less density or the greater the compressibility of the medium, the lower the speed of sound transmission. The temperature it can also influence the matter.

Thus, the propagation of sound cannot occur if there is no material medium whose molecules may vibrate. For this reason, an explosion in outer space could not be audibly perceived, while the sound of a train arrival, for example, reaches us thanks to the sound wave being transmitted through the air.

Sound properties

Instruments can play the same notes, but each with its respective timbre.

Broadly speaking, sound has four great properties:

  • Height or tone. According to their frequency, sounds are classified into treble (high frequency), medium (medium frequency) and bass (low frequency). Frequency is what distinguishes musical notes from each other.
  • Duration. It is the time during which the vibrations that a sound produces are maintained.
  • Intensity. It is the acoustic power (amount of energy per unit time) per air unit, and is measured in decibels (db). A sound is audible by the human above 0 db, and produces pain above 130 db.
  • Doorbell. 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 and others of lower intensity, the timbre is related to the intensities and varieties of those other frequencies that accompany the fundamental.

Musical sound

Music is the rhythmic and ordered set of sounds, generally those coming from musical instruments and the human voice (song). The distinction between music and noise is cultural in origin and has to do with considerations of harmony and beauty of the time.

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