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Fundamental of Noise Control:دار جامعة عدن للطباعة والنشر تصدر كتاب بعنوان

الجمعة - 10 يناير 2014 - 11:01 ص بتوقيت عدن

Fundamental of Noise Control:دار جامعة عدن للطباعة والنشر تصدر كتاب بعنوان



أصدرت دار جامعة عدن للطباعة والنشر كتاب جديد ضمن

سلسلة الكتاب الجامعي لعام 2013

بعنوان: 


Fundamental of Noise Control

Dr.Abdul Mannan Fareed

 



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Noise is unwanted sound. The word noise in this book is used to mean the common unwanted sounds such as traffic and noise produced in factories by machines and other activities, etc.  Noise is undesirable because it causes distraction by interfering with the mental activities and speech. It also masks the satisfactory hearing of speech and music. Sustained exposure to high-level noise has dangerous effects on physical and mental conditions of an individual. It results in fatigue, inefficiency, deafness or even nervous breakdown. A noise level of 130 db may be sufficient to rupture human eardrums.

Noise is a complex conglomeration of routine environmental and industrial operation. For noise insulation design one may restrict to either environmental noise or industrial noise alone depending upon the situation. In environmental noise, one has to take into account the noise from radios, blaring loud speakers, traffic and the indoor noise such as running water taps, fans, banging of door and window shutters, dragging furniture, etc.  The factory noise from  lathes, planning machines, drilling machines, forge hammers, running trolleys, exhausts, etc. comprises the industrial noise.

It is the business of the design engineer or architect to see that he designs a building, a workshop or workstation for less noise and better hearing. The talk of less noise and better hearing is similar to conditioning the building with respect to sound. Sound conditioning of a building is as important as air-conditioning for human comfort. Noise and sound can be differentiated in the same way as we differentiate between a friend and an enemy. Physically both are same, and therefore can be studied under a common group. But the ways to deal with them must differ characteristically. Whatever noise or sound may mean to a scientist, it is only a problem of vibrations. It is not only the design engineer, who is concerned about noise control; the scientist who wants to make precise measurements is equally concerned about the interference of noise or any minor vibration that may creep into his cell and disturb his delicate experimental set-up.

Faculty of Engineering, University of Aden, has academic regulations to update its plan of studies and curriculums in the various departments every 5 years to include the advancement in technologies and engineering fields into the curriculums and to prepare the study plans, their contents and undergraduates students to be able to work in the engineering and industrial sectors efficiently. The idea of preparing the materials of this book came in the year 2003, when the Faculty of Engineering introduced in the Mechanical Engineering Department three options; namely: Applied Mechanics, Thermal Engineering and Production & Industrial Engineering. Goals of these developments in the Mechanical Engineering Department were to undergo into the process of preparing graduates, who are scientifically oriented in the above fields of specialisations to enable them tackling engineering problems in a better and offering better understanding of the problems.

 

In order to design suitable and world-wide competent option in Applied Mechanics, references have been made to various universities and institutes for selecting suitable subjects for this option. One of these subjects was Noise Control to be given as an elective subject to the final year students in Applied Mechanics. In order to put the suitable chapters and knowledge into this subject, we made visits to various industrial and power generation sectors inside and around Aden Governorate. We tried to discuss the noise problems with concerned parties to know their problems and technical requirements to solve noise problems not only in the industry, but also in our society. We found that most of the administrations, engineers, trade union members and leaders have absolutely no idea about the noise effects on machines, workers’ health and working environment as well as about ISO Standard and OSHA regulations that organise the working hours under high noise levels to avoid exposure of workers to hearing damage and other health impairment. This put us into a new challenge. Therefore, we decided to build the chapters of this book in such a way that the students and other readers interested in noise control fields get a complete picture of the noise control subject in the following order:

  • Chapter one defines the various characteristics of the term noise, units of noise measurements, definitions of sound pressure and sound power levels and their summation and relationships between them.
  • While chapter two discusses in detail the various noise measuring variables available in the practice, permitted noise levels, as well as speech interference issue in front of high noise levels. The effects of noise on workers are also introduced. Standards available world-wide that are adopted in different countries, ISO Standard and OSHA regulations, are also introduced to calculate exposure times for particular nose levels.
  • Methods of controlling noise at source is thus discussed in some details and the discussion of the principles of vibration isolation and thus the reduction in noise levels using suitable flexible mountings or vibration isolators is given in Chapter three.
  • Chapter four shows lay-out of basic noise measuring systems and the various devices used for noise measurements, their technical specifications, standard noise measuring procedure, noise report and noise mapping are also described using suitable examples.
  • Finally, chapter five introduces and methods of noise control at path using sound absorbing and barrier materials to avoid noise propagations in factories and rooms.

The above design of the topics covered in this syllabus was executed to fulfil the following objectives:

  • To study fundamentals of sound and make basic calculations,
  • To study effects of noise on workers and community; and study the various standards concerning the calculation of safe noise exposure time,
  • To study methods of noise control at source; by isolating machine noise using flexible mountings,
  • To study noise measurements instruments, measurement standards, calibration, noise mapping and.
  • To study methods of noise control at path using absorbing materials, barriers, enclosures etc., and finally to study noise control at receiver using hearing protection devices.

To collect the materials of this book, a number of text books, references, manufacturers’ data sheets and brochures as well as published papers have been considered. To prepare suitable problems, the author had supervised a few final-year projects, also organised a number of training courses in Basics of Noise Control and made a number of experimental investigations in Aden Refinery Company, Aden Cement Enterprise, Badr Power Station, Al-Barh Cement Plant,  to measure the noise levels at critical situations and prepared noise mapping in Aden Refinery Company to help the concerned authorities identifying noise problems and to take suitable measures to solve these problems.

This textbook has been written mainly for mechanical engineers, civil engineers, architects and students taking up courses in noise control. It explains the fundamentals of acoustics systematically and supplies a number of useful tables of acoustical materials illustrating their use. In this book, a few practical applications of noise problems at various industry sectors are considered

List of Contents:

Chapter 1: Characteristics of Sound  1

1.0 Introduction  1

1.1 Sound Propagation  1

1.2 Sound Velocity    4

1.3 Sound Power, Sound Energy Density and Intensity  6

1.4 The Logarithmic Scale Decibel  7

1.5 Sound Power Level  8

1.6 Sound Pressure Level  12

  1.6.1 Adding Equal Sound Pressure Levels  12

1.6.2 Adding Unequal Sound Pressure Levels  14

1.7 Noise Spectrum  18

1.7.1 Octave Bands  20

1.7.2 One-third Octave Bands  24

1.8 Sound Reflection  24

1.9 Sound Diffraction  28

1.10 Sound Refraction  31

1.11 Sound Resonance  33

1.12 Sound Absorption  35

1.13 Sound Transmission Loss  36

1.14 Sound Sources  37

  1.14.1 The Plane Source  37

  1.14.2 The Point Source  37

  1.14.3 The Line Source  39

  1.14.4 Attenuation by Distance  40

1.15 Sound Pressure Level and Sound Power Level  44

1.16 Calculating Sound Power from Sound Pressure  53

Chapter 2: Effects of Noise Exposure  61

2.0 Introduction  61

2.1 The Hearing Mechanism  67

2.2 Loudness Determination  71

2.3 Loudness of Short Duration  74

2.4 Age-related Hearing Loss – Presbycusis    77

2.5 Noise-induced Hearing Loss  78

  2.5.1Steady Noise    78

  2.5.2 Impulsive Noise  80

2.6 Subjective Rating Scales of Noisiness and Annoyance  81

  2.6.1 Overall Sound Pressure Level dB  83

  2.6.2 A-weighted Sound Level  83

  2.6.3 Equivalent Continuous Sound Level  85

  2.6.4 Day-night Average Sound Level  86

  2.6.5 Noise Pollution Level  86

  2.6.6 Traffic Noise Index  87

  2.6.7 Perceived Noise Level  87

  2.6.8 Noise and Number Index  88

  2.6.9 Single Event Noise Exposure Level  88

2.7 Community Noise Annoyance Criteria  90

2.8 Speech Interference Criteria  95 2.9 Hearing Damage Risk Criteria    `  98

  2.9.1 Noise Exposure Limits       100

  2.9.2 OSHA Noise Regulations    109

Chapter 3: Noise Control at Source    117

3.0 Introduction    117

3.1 Alteration of Machines and Equipment    120

  3.1.1 Machines    120

  3.1.2 Equipment    121

  3.1.3 Material Handling    122

  3.1.4 Surface Damping    123

  3.1.5 Other Simple Treatments    123

3.2 Vibration Isolation of Machines    124

  3.2.1 Principles of Noise Reduction    124

  3.2.2 Principles of Vibration Isolation    125

  3.2.3 Vibration Isolators & Compliance Characteristics  128

  3.2.4 Damping, Friction and Energy-dissipation Characteristics      130

  3.2.5 Calculation of Force Transmissibility    132

3.3 Selection of Vibration Isolators    146

  3.3.1 Vibration Isolation Efficiency     146

  3.3.2 Multi-degree of Freedom System, Coupled Modes 149

  3.3.3 Static Load Distribution Calculation    152

  3.3.4 Procedure for Selection of Vibration Isolators    154

Chapter 4 Noise Measurements and Instruments  165

4.0 Introduction    165

4.1 Purpose of Noise Measurements    165

4.2 Frequency-weighting Networks    167

  4.2.1 Decibel Weighting Scales A, B and C    167

  4.2.2 Time Constants    170

4.3 Practical Noise Measurement Procedure    172

  4.3.1 Determining Noise Measurement Positions in Closed   Rooms      172

  4.3.2 Measurements in Open Air (Field Fields)    173

  4.3.3 Noise Mapping    174

4.4 Instruments for Noise Measurements   175

  4.4.1 Basic Noise Measuring Systems    175

  4.4.2 Portable Sound Level Meters    176

  4.4.3 Measuring Microphones    182

  4.4.4 Calibrations    189

  4.4.5 Noise Data Storage Systems    191

4.5 Laboratory Measurements and Analysis    193

  4.5.1 Laboratory Measurements    193

  4.5.2 Field Measurements    196

4.6 External Influences on Noise Measurements    196

  4.6.1 Influence of Instrument and Operator    196

  4.6.2 Influence of the Environment    197

  4.6.3 Environmental Noise    198

4.7 Standardisation of Noise Measurements    203

  4.7.1 Measurement Reports    203

  4.7.2 Using Noise Rating Curves    204

  4.7.3 High-levels Noise    205

  4.7.4 General Rules to follow During Measurements   207

Chapter 5: Noise Control Techniques    233

5.0 Noise Control    233

5.1 Sound Absorbing Materials    236

  5.1.1 Prefabricated Materials     236

  5.1.2 Blankets    236

  5.1.3 Acoustical Plasters    237

  5.1.4 Curtains    237

  5.1.5 Special Acoustical Arrangements    238

5.2 Recommended Noise Levels    239

5.3 Sound Absorption    244

  5.3.1 Sound Absorption Coefficient    244

  5.3.2 Noise Reduction    247

5.4 Reverberation of Sound    247

5.5 Shields & Barriers    255

  5.5.1 Barrier Design    257

  5.5.2 Noise Insulation Factor     263

5.6 Mass Laws of Barriers    269

  5.6.1 Transmission Loss of Single Wall Panels    271

  5.6.2 Transmission Loss of Double Wall Panels    272

5.7 Wood Structural Panels    274

  5.7.1 Single Wood Panels    275

  5.7.2 Double Wood Panels    277

5.8 Acoustical Enclosures    282

  5.8.1 Partial Enclosures    282

  5.8.2 Total Enclosures    285

  5.8.3 Ventilation of Enclosures    289

Appendices    297

Bibliography    339