We explain what sound is and what its general characteristics are. Also, its speed, differences with noise and more.
What is sound?
Sound is the consequence of the vibratory movement of a body , which when vibrating generates pressure variations that propagate through an elastic medium, such as air , for example. It should be clear that in the production of sound there is transport of energy , without any movement of matter .
Sounds are perceived by the ear , which detects these pressure variations, but not all (this depends on the frequency of the vibration). For example:
- The human being . It cannot pick up vibrations with a frequency of less than 20 Hz, nor more than 20,000 Hz, so those between these two values are perceived.
- The dogs . They can pick up sounds in the range of 20 to 65,000 Hz.
- Bats . They can perceive sounds in the range of 120 Hz to 250,000 Hz.
While sound transmits very well through air , it transmits even better through solids and liquids . In a vacuum, sound cannot be transmitted due to the lack of material that can propagate vibratory waves.
How is sound produced?
Acoustics is the branch of physics that analyzes sound.
- It is generated by vibrations . Sound is generated by vibration of some kind of body. Sound is a physical phenomenon and the branch of physics that studies it is called acoustics.
- Use a transmission medium . To be transmitted, sound needs some medium, which can be solid, liquid or gaseous. The speed of sound propagation depends, among other things, on the density and temperature of the different media.
- Spreads energy . Sound is a wave that propagates energy . This energy is the one that generates the source that produces the sound when vibrating and that is translated into the kinetic and potential energy of the particles of the medium through which the wave is transmitted.
Sound intensity is measured in decibels.
Intensity . It is the force with which the sound is perceived and depends on the amplitude of the oscillatory movement. Physically, intensity is the amount of energy that a sound wave propagates per unit of time and per unit area, that is, it is the power of a wave per unit area. Subjectively, we say that a sound is strong or weak. When we turn up the volume of the radio , what we do is increase the intensity of the sound. Intensity is measured in decibels. A murmur is about 25 decibels; an explosion can have an intensity of 140 decibels and damage the hearing.
Height . It is the number of oscillations per second. Depending on its height, a sound can be low or high. The higher the frequency, the higher the sound is. The lower the frequency, the more serious.
Timbre . It is what makes it possible to differentiate the source of the sound. Thanks to the timbre we can distinguish sounds of equal intensity and height. For example, by the timbre of a sound, we are able to distinguish human voices from each other or the sound of different musical instruments.
Thanks to the timbre we can distinguish sounds with equal frequency and intensity.
Duration . It is the time that the vibration lasts. It can be long, like a fire engine siren, or short, like a snap of the fingers.
Echo . It is the reflection of sound and occurs when the vibratory wave encounters perpendicular surfaces in its path. The human ear is capable of distinguishing two consecutive sounds as long as they have been emitted with a difference of at least 0.1 seconds. Depending on the speed of sound propagation in the medium, in order to perceive the echo, a certain distance is needed between the source of the sound and the reflecting surface.
Sound or noise
Difference between noise and sound We usually make the distinction between sounds and noises.
- The sounds . They are those that produce a pleasant sensation, because they are musical or harmonic, which is closely related to the type of frequencies that the sound wave contains.
- The noises . They lack periodicity because they are produced by waves with a very high number of frequencies (compared to those that produce sounds) and it is precisely this peculiarity that leads to an unpleasant or annoying brain-sensory sensation.
The inner ear is responsible for transmitting the signals to the brain.
The sound is perceived thanks to the operation of the hearing aid. Inside our ears, sound waves move small components called ossicles that transmit movement from the eardrum to the inner ear. The inner ear is then responsible for transmitting the signals to the brain , via the nervous system .
Speed of sound
The speed of sound is the speed with which sound waves propagate , under certain conditions of pressure and temperature, in a given medium. The more solid the medium through which the sound wave travels and the higher its temperature, the greater the speed of sound.
In the air, if we consider 50% humidity in the environment, a temperature of 20ºC and altitude at sea level, the speed of sound is 1235 km / h or 343 m / s. Under the same conditions, but in water , the speed of sound is 1482 m / s, about 4.3 times higher.
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