5 facts about sound waves

These five facts about sound waves show that physical concepts are often opposed to common sense perceptions.

The mismatched relationship between pitch and volume is one of the characteristics of sound waves.
The study of sound waves reveals some curiosities that, in most cases, are beyond what common sense thinks. Correctly understanding the characteristics of sound waves can provide a better understanding of wave phenomena and characteristic expressions of Physics . See five curiosities about these waves!

1) The pitch of the sound is not related to volume

Daily it is common to relate the words alto and bass to the volume of a given sound source. From a physical point of view, pitch is not related to the volume of the sound, but to the frequency of the waves emitted . The higher the frequency of a sound wave, the higher the sound, which will be called loud. On the other hand, the lower the frequency of the sound waves, the more serious the sound, which will be called low sound.

Loud sound = high pitched sound = high frequency

Low sound = bass sound = low frequency

Volume is related to sound intensity , the amount of energy emitted by the sound source in a given time interval . When changing the volume of a sound source, the only characteristic of the wave that changes is the amplitude.

2) Sound cannot be polarized

Polarization is the process of “filtering” the passage of a given wave through a wave-selecting material called a polarizer. Only transverse waves can be polarized. Sound is a longitudinal wave , that is, its vibration is parallel to the propagation Longitudinal waves cannot undergo polarization. 3) There are sounds we cannot hear
The human ear has a lower and upper limit of audible frequencies. Any sound frequency between 20 Hz and 20,000 Hz can be perceived by the human hearing aid . Sounds below 20 Hz do not sensitize the ear and are called infrasound . Frequencies greater than 20,000 Hz are too high to be picked up by the ear and are called ultrasound .

4) Sound is faster on solids

Sound waves are mechanical , which means they need a medium to propagate. The proximity of the molecules that make up the propagation medium influences the speed of sound. Therefore, the speed of sound is higher in solid materials , because in this physical state the proximity between the molecules is maximum .

SOLID > V LIQUID > V GASES

Speed ​​of sound in iron ≈ 5000 m/s
Speed ​​of sound in water ≈ 1500 m/s

Speed ​​of sound in air ≈ 340 m/s

5) Sound is 1 million times slower than light

The speed of light corresponds to 3 x 10 8 m/s, that is, 300 million meters are covered in just one second of displacement. The speed of sound is incomparably lower and reaches values ​​corresponding to 340 m/s. Light is approximately 1 million times faster than sound.

The clear perception of this difference is in the observation of lightning and thunder . Always after lightning comes thunder. The light emitted by the electrical discharge reaches our eyes in a longer time than the bang produced by the expansion of air masses, so we always see lightning and, later, hear thunder.

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