الضجيج - الصوت .. الفيزياء

Noise - Sound .. Physics

Noise

Noise is defined as an annoying sound with a fluctuating frequency that is not palatable to its listener. Our environment is full of noise that comes from different sources, such as air, traffic, factory sounds, and amplified music, and therefore lawmakers have been keen to enact many laws to limit its height.

It is worth noting that the intensity of sound is usually measured by comparing its ability with the ability of another sound that the ear can only distinguish with extreme difficulty. Since the human response to light and sound is proportional to the logarithm of the stimulus causing the sound itself, a logarithmic unit called the decibel was used to measure it, which is equal to (dB = (10/1) log 10 (r / r 5)

A single sound is usually characterized by its constant frequency. As for a moving sound, such as a train whistle at a railway station, for example, it gives the listener a feeling of a decrease in its pitch as soon as the train passes near the observer's location at the station. This is an example of the Doppler effect, which usually occurs in cases where the sources of light and sound are moving. The distance traveled by a certain sound wave after a period of time of n, n, or years is determined by a group of circles, each of which is called the wave front, which is emitted from the source every n seconds, and the source is the center of all of them at the same time.

(Classification of different sounds by decibel)
(Standard sound waveforms)

It is worth noting that these wave fronts become crowded when the source moves at a speed of n in the direction of the same movement And they move away from each other if it is moving in the opposite direction. It is known that the distance between two wave chests is proportional to the wavelength itself, and that the speed of sound waves in the air is constant (332 m/s) and equals the product of the wavelength and its frequency. As a result, the observer feels a decrease in the wavelength, i.e. an increase in its frequency, the closer the moving source gets to him, according to the following equation: N = N5 E / (E - E5), where N5 represents the frequency of the source when it is not moving. However, if the source moves away from the observer, the circles move away from each other and the frequency value decreases according to the equation N% N5 E / (E + E5). It is worth noting that this change in the difference in the pitch of the sound only occurs at the moment when the source passes by the observer.

The wave chests become more crowded as the speed of the source itself increases. When the plane's speed reaches the speed of sound, the circles close together, creating a sonic boom similar to an explosion, which is the result of a sudden drop in pressure, generating what is called a shock wave.