Differences between sounds and noise
When talking about noise, you often think of an uncomfortable sound, sometimes extremely painful. From a physical standpoint, noise is a complex mixture of various sound frequencies, which are generally distinguished as stationary noises (those who have practically no fluctuations with time) and non-stationary noises (which have roughly strong fluctuations).
Stationary noises could be emitted by an electric motor, a fan or a compressor rotating steadily. Noises of a non-stationary nature are those emitted by a press, or due to metal parts falling in a container. Another typical example of non-stationary noise is the traffic noise. In terms of noise control issues, we often find two types of noise.
The Source of Noise: Sound Waves
In a very simple way, we can say that:
• Sound is produced by the wave motion of an elastic medium (usually air), due to rapid changes of pressure generated by the vibratory movement of a sounding body.
• Noise is considered an annoying and unwanted sound.
It is also important to know that:
NOISE = AIR MOVING
And that noise passes through the air.