Sound waves

Sound waves are types of mechanical, longitudinal and three-dimensional waves that propagate with greater speed in solid media.

Our daily lives are full of sound wave sources, types of mechanical, longitudinal and three-dimensional waves.

Sound waves are constantly present in our daily lives and can generate in us, for example, feelings of tranquility and stress. Sound is classified as a mechanical wave (it needs a propagation medium), longitudinal (it has propagation parallel to the vibration) and three- dimensional (it propagates in all dimensions).

sound propagation speed

The speed of propagation of sound waves depends on two basic factors: the physical state of the medium through which the waves propagate and the temperature . As for the physical state of the medium, the greater the proximity between the molecules of the medium, the faster the sound, so sound waves are faster in solids, then in liquids and, finally, in gases.


Temperature directly influences the speed of propagation of sound waves, therefore, the higher the temperature of a gas, for example, the greater the speed of propagation of sound.

sound spectrum

The sound spectrum shows the range of frequencies that are audible to humans. The human hearing aid has the ability to perceive sound frequencies between 20 Hz and 20 kHz, and any frequency above or below these values ​​is inaudible to humans.

Frequencies below the minimum perceived by the human ear (20 Hz) are called infrasound . Animals such as dogs and cats, because they have a greater hearing capacity, can perceive sounds that for humans are considered infrasound.

Frequencies above the maximum perceived by the human ear (20 kHz = 20,000 Hz) are called ultrasound . Animals such as bats and dolphins produce ultrasound for their locomotion and hunting. We use ultrasonic waves , for example, in ultrasounds , diagnostic imaging.

physiological qualities

The physiological qualities of sound waves are related to our ability to perceive incoming sounds.

  • Height : Quality related to the frequency of sound waves. Height has nothing to do with volume.

Loud sound = High frequency sound = High sound

Low sound = Low frequency sound = Bass sound

  • Timbre : Quality related to the shape of sound waves produced by a source. Even if two different sources emit sounds with the same characteristics, each source emits waves with different shapes and, thus, are perceived differently. It is said, then, that each sound source has a characteristic timbre .
  • Intensity : Quality related to the energy emitted by a sound source that crosses a given surface within a certain time interval. Intensity is related to thevolume of sound emitted by a source.

I = P

Intensity is defined as the ratio of the power of the sound source to the area hit by the waves. According to the International System of Units , the unit of measurement for intensity must be w/m 2 .

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