BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE Day 3 3

BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE 职业卫生基本原则 Day 3 第 3天

13 – NOISE 13 -噪音

NOISE 噪音 • • Noise is unwanted sound. 噪音是有害的。 Known for many years as a cause of hearing loss in industry. 多年前就已确定，噪音是 业听力损失的原因之一。 Sound is the sensation that is perceived by the human or animal brain as a result of longitudinal vibrations of molecules of the air impinging on the ear. 声音是空气分子的纵向振动撞击耳朵，导致人类或动物 大脑有感知的能量。 Sounds are actually pressure waves caused by a vibrating body, which radiate from the source. 声音是声源振动产生的压力波。

The Ear 耳朵 External Ear外耳 Source: Wikimedia Commons 资料来源：维基共享资源 Middle Ear鼓室 Cochlea耳蜗

Audible Sound可听音 Two key features of sound are frequency and intensity. 声音的两个主要特征是频率和强度。 • The number of pressure waves/vibrations per second is known as the frequency, and is expressed in the unit Hertz (Hz) • 频率系指每秒压力波/振动的次数，单位是赫兹（Hz）。 • The more fluctuations per second the higher the pitch of the sound • 每秒波动次数越多，音高越高。 • By intensity (I) we mean the amplitude (size) of the pressure waves and is defined as the average amount of energy passing through a unit area in unit time (Wm 2). • 强度（I）系指压力波的振幅（大小），是单位时间通过单位面积的 平均能量（ Wm 2 ）。

Health Effects of Excessive Noise 过量噪音对健康的影响 • Noise Induced Hearing Loss (NIHL), a cumulative effect from repeated exposure and it is due to damage to the hair cells of the cochlea in the inner ear. • • 噪声导致听力损失（NIHL）是反复接触的累积效果，因内耳的耳蜗毛细胞受损所致。 • • • Tinnitus - Noise heard in the ear without external cause, frequently accompanies deafness. 耳鸣——外部无声音，但听到声音，通常伴随耳聋。 Temporary Threshold Shift (TTS) - Damage to the hair cells of the inner ear which can impair hearing temporarily, resulting from exposure to high noise levels. 一时性听力障碍（TTS）——因接触较高噪音，导致内耳毛细胞受损，可能会暂时出现听力受损。 Physical damage to the eardrum and ossicles induced by excessively high noises e. g. explosions. 因过量噪音，如爆炸等，导致耳膜和听小骨受损。 Annoyance/stress, which is difficult to measure and quantify, but may cause psychological effects such as poor concentration, irritability and stress. 烦躁/压力：难以度量和量化，但可能会造成的心理影响，如注意力不集中，烦躁不安和压力大。

Addition of Sound Levels 声级相加 • • • When two sounds are being emitted at the same time their total combined intensity is not the numerical sum of the decibel levels of each sound. 当同时出现两个声音，其声音总强度不是各声级强度的总和。 For accurate calculations they must be added as logarithms – usually using a calculator. 为确保计算精准，因采用对数方式相加——通常使用计算器来计算。 Alternatively a reasonable approximation of additions of decibel levels can be made. 或者，还可以取声级之和的大致近似值。 Difference in d. B (A) 分贝（A）差 Add to the Higher 加到较高者上 0 or 1 0或 1 3 2 or 3 2或 13 2 4 to 9 4至 9 1 10 or more 10或以上 0

Addition of Sound Levels 声级相加 Doubling of the Pressure increases noise levels by 3 d. B 压力加倍，噪音等级提高 3 d. B。

Frequency Analysis 频率分析 倍频带 频率 Source: Castle Group 资料来源：Castle Group

Decibel Weightings 分贝加权 • As the human ear is more sensitive to certain frequencies than others, it is possible to make allowances for that in the electronic circuitry of a sound level meter. • 由于人耳只对某些频率有感应，对另一些频率则没有感应，所以可以在电子环境中 新增声级计。 • Certain frequencies are suppressed whilst others are enhanced in order to approximate to the response of the human ear. • 抑制某些频率时，可能会导致其他频率加强，以确保人耳能对其进行回应。 • Known as weighting and there are A, B, C and D weightings available for various purposes. The one that has been adopted for a workplace spectrum is given in d. B(A). • 目前有A、B、C和D声级加权，用途广泛。 作场所频谱采用的声级加权是分贝（A ）。

Equivalent Continuous Sound Level (Leq) 等效连续声级(Leq) 噪 音 级 时间 Leq can be defined as the steady sound pressure level, which over a period of time has the same energy content and consequently the same hearing damage potential as the actual fluctuating noise. 等效连续声级可以定义为稳定的声压声级，在一段时间内具有相同的能量，因此，当实际噪音波动时，会 出现潜在听力丧失。 Source: Adrian Hirst 资料来源：Adrian Hirst

Noise Dose 噪音计量 Duration per Day (hours) 每日持续时间（小时） European Limit (Leq ) d. B(A) 欧洲限值 (Leq ) d. B(A) 16 82 8 85 4 88 2 91 1 94 30 min 97 15 min 100 7. 5 min 103 3. 75 min 106

Noise Limits 噪声限值 European Limits: 欧洲限值： • Lower exposure action values: a daily or weekly personal noise exposure of 80 d. B (Aweighted) and a peak sound pressure of 135 d. B (C-weighted). • 低暴露行动值：每日或每周个人噪音限值为 80 d. B （A加权），声压峰值是 135分贝（C-加权）。 • Upper exposure action values: a daily or weekly personal noise exposure of 85 d. B (Aweighted) and a peak sound pressure of 137 d. B (C-weighted). • 高暴露行动值：每日或每周个人噪音限值为 85分贝（A加权），声压峰值是 137 分贝（C-加权）。 • Exposure limit values: a daily or weekly personal noise exposure of 87 d. B (A-weighted) and a peak sound pressure of 140 d. B (C-weighted). • 暴露限值：每日或每周个人噪音限值为 87分贝（A加权），声压峰值是 140 分贝（C-加权）。 Other Limits 其它限值 • In the USA a more complex set of criteria is used which correlates dose with sound pressure level and time. This is known as a 5 d. B doubling concept and is largely discredited outside of the USA. • 美国的标准更为复杂：将计量与声压等级和时间相关联，即 5分贝规则，但在美国境外使用不多。

Assessment of Workplace Noise 作场所噪音的评估 Noise Meter Noise Dosimeter 噪音剂量计 Source: Wikmedia Commons 资料来源：维基资料共享

Control of Workplace Noise 作场所噪声的控制 • • Reduction of noise at source - best achieved at the design stage 减少噪音源——最好在设计阶段实现 Enclosure of noisy equipment - although heat dissipation and access for maintenance can be a problem. 隔离噪音设备——虽然散热和维护接触可能会是问题。 Screening of noisy equipment from the worker and/or increased separation of the worker from the noise source(s) 从 作人员角度对噪音设备进行筛选和/或增加 作人员与噪音源的 隔离强度。 Absorption of sound by the cladding of appropriate surfaces with sound absorbent material where reverberation can be a problem. 通过使用吸音材料适当覆盖表面来增加吸音强度，但可能会出现混 响问题。

Protection of Personnel at Risk 对受噪音风险的人员提供保护 • • • Provision of Noise Refuges in designated areas. 在指定区域提供噪音庇护所 Alteration of the Work Pattern. 更改 作模式。 Use of Personal Hearing Protection Devices, e. g. ear muffs, ear plugs. • 个人听力防护装置的使用，例如耳罩，耳塞等。 Source: Wikmedia Commons 资料来源：维基资源共享