"Noise and Environmental Protection" Acoustic Phenomenon PPT Courseware 3

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"Noise and Environmental Protection" Acoustic Phenomenon PPT Courseware 3

noise

Noise is noise. It is a type of sound that causes people to be irritated or whose volume is too strong and endangers human health.

Noise is a subjective evaluation standard, that is, all sounds that affect others are noise, whether it is music or mechanical sound, etc.

From the perspective of environmental protection, all sounds that affect people's normal study, work and rest, as well as "unwanted sounds" that people make on certain occasions, are collectively called noise. Such as the roar of machines, the sound of motors and whistles of various vehicles, the noise of people and various sudden sounds, etc., are all called noise.

From a physical point of view - music and noise are caused by the vibration of the sound source. The difference is: musical sound is formed by the vibration of periodic sound sources, and its wave image is a periodic curve. Noise is emitted by irregular or non-periodic vibration sound sources, and its wave image is irregular. regular curve,

Noise is "a sound composed of sounds of different frequencies and loudness mixed together irregularly". It is the superposition of multiple messy sound waves.

Source of noise

There are four main sources of environmental noise in modern cities:

Traffic noise: mainly refers to the noise emitted by motor vehicles, airplanes, trains, ships and other means of transportation during operation. The noise sources of these noises are mobile and have a large interference range.

Industrial noise: mainly refers to the noise generated in industrial production labor. Mainly from machines and high-speed running equipment.

Construction noise: mainly refers to the noise generated at the construction site. During construction, a large number of various power machines are used, excavation, drilling, mixing, and materials and components must be transported frequently, thus generating a lot of noise.

Social life noise: mainly refers to the noise generated by people in various social activities such as commercial transactions, sports competitions, parades and rallies, entertainment venues, etc., as well as the noise from various household appliances such as radio recorders, televisions, and washing machines. This type of noise is generally found in Below 80 decibels. For example, the noise of washing machines and sewing machines is 50-80 decibels, the noise of electric fans is 30-65 decibels, and the noise of air conditioners and televisions is 70 decibels.

3. Control noise

Measures to control noise can focus on three parts. Noise control content includes:

Control noise sources

To reduce sound source noise, industry and transportation industries can choose low-noise production equipment and improve production processes, or change the movement mode of the noise source (such as using damping, vibration isolation and other measures to reduce the vibration of solid sound emitters).

Block noise transmission

Reduce noise on the sound transmission path, control the spread of noise, and change the noise propagation path that the sound source has emitted, such as using sound absorption, sound insulation, sound barriers, vibration isolation and other measures, as well as rational planning of urban and building layout, etc.

Reduce noise at the human ear

When measures cannot be taken to protect the sound source or the sound-receiving organ from the noise of the sound source or the sound-receiving organ, or the acoustic measures taken still cannot achieve the expected effect, it is necessary to take protective measures for the sound-receiving person or the sound-receiving organ, such as Workers with long-term occupational noise exposure can wear ear protection such as earplugs, earmuffs, or helmets.

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Update Time: 2024-11-12

This template belongs to Physics courseware Beijing Normal University eighth grade physics volume one industry PPT template

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