How do sound waves work

sound

If you hear the term "sound", you surely know what it is talking about. Here you can also find out what sound actually is and how you perceive the world around you with your ears.

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Schall simply explained

At the sound is it a wave. These Sound waves reach your ear and let you perceive sounds and noises through your ear-brain system. There are generally two distinctions: the Useful sound and the Noise. The useful sound includes music or voices in a conversation. Background noise includes construction site noise or traffic noise.

In physics is sound a vibration. This vibration spreads as mechanical shaft (also acoustic wave) in one medium out. Such a medium is the air, for example. But you have probably already heard noises underwater or through walls. At Sound waves in the air it is a matter of fluctuation in print and the density

What is sound?

sound is a suggestion. This means that an event like uttering words will make the air vibrate. This suggestion then spreads as Wave motion out. In addition to air, other elastic media such as water can also be stimulated.

Sound is a mechanical wave that propagates in a room through changes in air pressure and air density.

How fast is the sound?

The Speed ​​of sound is largely dependent on medium, whose temperature and print. In dry air at 20 ° C, the speed of sound is 1236 km / h (343.2 m / s meters per second). The following table gives you a few reference values ​​for the speed of sound in different media.

mediumSpeed ​​in m / s
air343
Water vapor (at 100 ° C)477
water1484
Water (at 0 ° C)1407
Sea water1500

In our article on, we explain to you how quickly sound spreads in different materials Speed ​​of sound. The properties of solids, liquids or gases play an important role here.

Sound properties

There sound a mechanical shaft is, it also has the properties of a wave like frequency and intensity. However, the medium through which it is transmitted also gives it its own properties.

Here we go into the general properties of sound in air. As a rule, these can also be transferred to other gases and liquids. waves in air or other gases is also known as longitudinal waves. These vibrate in the direction of the wave's propagation direction. Opposite are the transverse waveswhich arise, for example, in some solids. Their oscillation is perpendicular to the direction of propagation.

How is sound created?

sound is from Sound sources generated. A sound source is anything that causes the air to vibrate. Such a sound source can be a tambourine, for example. If you hit the tambourine, you will deform its surface. This has tension and accelerates back to its starting position. The air particles are accelerated, which leads to a change in pressure and density. Since the entire space around the tambourine is filled with air, this movement of the Air atoms away. The resulting mechanical shaft reaches a sound receiver, for example your hearing. This mechanical wave is one Sound wave.

How does sound propagate?

sound spreads, as already indicated in the example of the tambourine, through changes in pressure and density. The blow compresses the air at one point. This increases the pressure in this area. The density increases exactly at that point, but decreases around it. But since there are no walls holding the compressed air together, the compressed particles are pushed apart again. In doing so, they push neighboring air atoms, which have taken the place of the compressed air atoms, and thus press them together again in a different location. This is a shift in air pressure and is called wave designated. This then propagates to the recipient.

Frequency and sound waves

Like any wave, have, too Sound waves a frequency. With this you divide the sound spectrum into different categories.

  • Infrasound: This is low-frequency sound that is no longer perceptible to the human ear. <16 Hz (Hertz)
  • Audible sound: This is the sound that can be heard by humans. Ranges from 16 Hz to 20 kHz (kilohertz)
  • Ultrasound: This is high-frequency sound that is no longer perceptible to the human ear. Ranges from 20 kHz to 1.6 GHz (gigahertz)
  • Hypersonic: These are sound waves that can only propagate to a limited extent. > 1 GHz

Different types of sound

As you learned at the beginning, you divide the sound into useful and interference sound. You refine this classification by also introducing tone, sound, noise and bang as categories.

The tone is a sinusoidal oscillation, i.e. a sinusoidal signal. For example, if you strike a tuning fork, you will get a single, harmonic tone.

A sound creates a periodic, but not sinusoidal, signal. When you play a song on the guitar, you create such a sound.

A noise is a non-periodic and also non-sinusoidal signal. Noise is generated, for example, by machines and vehicles.

When there is a bang, there is a strong amplitude maximum, which then quickly subsides again. If you shoot a firework in the air or fire a blank gun, you will hear such a bang.

Sound intensity and sound level

Colloquially, the sound level also means volume. This describes the strength of the sound at a specific location. This can be measured physically as sound pressure. Starting from the source, the sound level usually decreases logarithmically. You use the unit decibel (dB) to denote it in mathematical formulas.

The sound intensity describes the sound power that passes through a sound-penetrated surface. You calculate this by measuring how much sound passes through the smallest sections of this area and integrates it over their entirety.