5 things you need to know about sound waves

Everyday we produce different sounds and are exposed to countless sound sources. Even if the sound is something so common in our daily lives, there are some characteristics that are not fully understood. See a list of five items related to physical principles that involve the sound waves.

→ Sound is faster on solid media

At sound waves are classified as mechanical waves, that is, they need a means for their propagation to be possible. Sound propagates through vibrations generated in the molecules of the material that makes up the propagation medium. The closer the molecules are, the greater the speed of the sound waves and vice versa. Molecules of materials in the solid state are closer than molecules of substances in the liquid and gaseous state, thus, the speed of sound is higher in solids.

THE temperatureaffects the speed of sound in liquids and gases, as variations in this magnitude can cause the molecules to move closer or further apart.

There are some reports of Indians putting their ears to the ground to detect the arrival of enemy troops cavalry. The sound waves produced by the galloping horses arrive first through the ground rather than through the air, which could give an advantage to a possible indigenous counterattack.

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→ Height is not related to volume

Everyday we say that the sound is high or low in reference to the volume, but from a physical point of view, volume and height are different definitions.

THE height is the characteristic related to the frequency of sound waves. The higher the frequency, the louder the sound and vice versa. Loud sound is defined as high sound, and low sound is bass sound. Thus, when we say that a sound is loud, it is because sound waves have a high frequency, which characterizes the sound as high-pitched.

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The volume is related with the intensity of the sound waves, that is, with the amount of energy produced by a sound source in a certain region of space and within a certain time interval.

→ Sound cannot be polarized

THE polarization is the selection of propagation directions of cross waves made by means of a kind of filter called a polarizer. Polarization is a phenomenon that can only occur with transverse waves, a type of wave that propagates perpendicular to the vibration. Sound waves cannot be polarized because they are longitudinal waves, that is, they have the propagation parallel to the vibration.

→ There are sounds inaudible to humans

O human hearing aid cannot capture all the sound waves that reach it, as there is a range of audible frequencies for the human ear. The human hearing capacity is comprised between the frequency range of 16 Hz to 20,000 Hz.

Sounds that have a frequency lower than the minimum of 16 Hz are called infrasounds. Sounds that have a frequency greater than the maximum of 20,000 Hz are called ultrasound. The audibility range is variable, that is, what for us is infra or ultrasound can be audible sound for another living being.

→ Light is extremely faster than sound

THE speed of sound waves in air it is only 340 m/s, and the speed of electromagnetic waves is 300,000,000 m/s. This stark difference is evident when we look at the rays and thunder. Lightning is always perceived before the sound produced by thunder.

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. "5 things you need to know about sound waves"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/5-coisas-que-voce-precisa-saber-sobre-as-ondas-sonoras.htm. Accessed on June 27, 2021.


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