What is sound?

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

What is sound?

What is the sound?

When we talk about sound, we mean 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, according to the characteristics of the transmitted waves, and the impact on them by the means by which they are transmitted.

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

Sound can also spread in other elements and substances, liquid, solid or gaseous, but often undergoing certain modifications. In any case it is a transport of energy without transport of matter, and unlike the electromagnetic waves of light or radiation, it cannot propagate in a vacuum.

These phenomena are studied by acoustics, a branch of physics and engineering that seeks to understand as much as possible the science of sound. It is also of great interest for phonetics, a branch of linguistics specialized in oral communication of human beings in their different languages.

Sound characteristics

Sound is produced when a body vibrates rapidly, and transmits these vibrations to the surrounding environment in the form of sound waves. These travel 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 sound boxes or speakers).

Whatever its origin, the sound has the following physical characteristics:

• Frequency (f): the number of complete vibrations per second that the sound source makes and that is transmitted in the waves. An audible sound by humans will have a frequency of between 20 and 20,000 Hz. Above that range will be an ultrasound perceptible to most animals.
• Amplitude: It is related to volume and intensity (acoustic power), and it has to do with the amount of energy transmitted in the waves.
• Wavelength ( λ ): The distance traveled by a wave in a given period of time , that is, the size of the wave.
• Acoustic power (W): It is the amount of energy emitted in the waves per unit of time determined. It is measured in watts and depends directly on the wavelength.
• Frequency spectrum: The distribution of acoustic energy in 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 the compressibility and density of 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. The temperature can also influence the matter.

Thus, the propagation of sound cannot occur if there is no material medium whose molecules can vibrate . That is why an explosion in outer space could not be perceived auditively, while on the metal rails of the train its coming can be perceived long before its sound reaches us through the air.

Sound properties

Broadly speaking, sound has four great properties:

• Height or tone. According to their frequency, the sounds are classified as high (high frequency), medium (medium frequency) and bass (low frequency). Frequency is what distinguishes musical notes from each other.
• Duration. Time during which a sound vibrates. There are long, short or very short sounds, for example.
• Intensity. The amount of energy contained in a sound, that is, its strength, which has to do with its amplitude and its acoustic power, is measured in decibels (db) and distinguishes between strong and weak sounds. A sound is audible above 0 db and produces pain to the human being above 130.
• Timbre. Sound typing based on its origin, that is, the nature of the sound according to its origin. Different musical instruments can play the same notes, but each one with its respective sound bell.

Musical sound

Music is the rhythmic and orderly set of sounds , usually those from musical instruments and the human voice (singing). The distinction between music and noise is conventional, that is, of cultural origin, and has to do with the considerations of harmony and beauty of the time.