Interfere with rest, study, life and work, and even affect the health of the sound, collectively referred to as noise. Noise consists of many pure tones. The sound pressure (p) of a pure tone (single frequency sound) is expressed in terms of sound pressure level (Lp) compared to the reference sound pressure (p0 is close to that of the average person, usually p0 = 2 × 10-5 Pa) (DB), its mathematical expression is Lp = 201g (p / p0). Determination of the strength of the noise is more complicated, not only to combine the frequency of pure tone, but also with the subjective feelings of people. There are many ways to measure, the general use of sound level, the unit also uses decibels. Sound level available sound level meter directly measured. Sound level increased 40 dB, sound pressure increased about a hundred times, greatly increased interference. Generally believed that less than 85 decibels will not affect hearing. Jet aircraft took off at 150 dB noise, making the ear drums hurt. 160 dB noise makes people deaf. Noise also affects the human central nervous system and cardiovascular system, leading to neurasthenia and cardiovascular disease. Noise also affects the speech and the use of the phone. Noise that can cause deafness also affects the use of certain instruments.

Noise comes mainly from machinery (industrial noise) and transportation (traffic noise). Noise control is not the first noise equipment: or the reform process, such as change the riveting for welding; or change the machinery, such as using pile driver instead of pile driver. Followed by the reform of mechanical structure and materials, such as improving the accuracy of parts to reduce collision, with non-metallic materials instead of metal materials, transmission components with elastic components, the machine uses vibration isolation base or noise enclosures, exhaust muffler set, transport Shape using streamlined and so on. Again the correct operation, such as the proper use of lubricants, the proper use of speakers and other audio equipment. Building sound insulation barriers (such as walls and mounds) or multi-purpose sound absorbing and sound insulating materials on building surfaces, as well as rational urban planning are also effective measures (see Airport Environmental Protection).