O sound is wave mechanical type, for it needs a means to propagate, and it is three-dimensional, since it can be perceived in all directions. The fact that it is three-dimensional restricts its form of propagation, which cannot be transversal, but rather, longitudinal, that is, the waves will have a propagation direction parallel to the vibration that generated them. At electromagnetic waves they are an exception because, even though they are three-dimensional, their propagation form is transversal.
sound spectrum
The human ear can only perceive sounds within a range of frequencies, which goes from at least 20 Hz until the maximum of 20,000 Hz. Sounds below the minimum audible are called infrasoundsand those above the maximum audible by the human being are called ultrasound. The sound spectrum shows the regions of the human hearing, as well as the infra and ultrasound regions. What for us may be infrasound or ultrasound may be audible sound for some animals, such as dogs.
Speed of sound
THE
speed of sound it depends on characteristics presented by the propagation medium. Density, temperature and pressure are decisive for obtaining the speed of sound waves.
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In the equation above, B is the volume modulus of elasticity, magnitude that indicates the greater or lesser capacity of the material to allow the passage of sound waves, and d is the middle density where the propagation of the waves will occur. The following table shows some propagation speed values for different media.
Note that the speed of waves is related to the connection or proximity of the particles that make up the material.
sound intensity
THE sound intensity is the greatness that determines the amount of energy that flows from a source and crosses a certain area, being defined as the ratio between the power dissipated by the sound source and the area of the region reached by it. According to International System of Units, the sound intensity must be measured in watts per square meter (W/m2).
The minimum power perceived by the human being is of the order of 10 – 12 W/m2. Through the quantity called sound intensity level, you can measure the sensation that sound produces on the human auditory system.
By Joab Silas
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
JUNIOR, Joab Silas da Silva. "What is sound?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-som.htm. Accessed on June 27, 2021.
