The tool makes minor repairs, assemblies, installations, and hundreds of jobs an easy undertaking. The quick- release design easily snaps to your key ring. Noise Control- A Guide for Workers and Employers. Noise Control A guide for workers and employers. U. S. Department of Labor. Occupational Safety and Health Administration. Contents. Noise. It can destroy hearing. It can create physical and psychological stress. And it can contribute to accidents by making it impossible. Academia.edu is a platform for academics to share research papers. More Like Blood ** At exactly 8 o’clock the elevator doors slid open to reveal Salome and her annoying youngest child her reason for. Zac – The Unlucky One. Marine Zachary thought he knew how to stand to attention, and hold a formal pose, but the Arab insisted. Shark Tank is an American reality television series produced by Mark Burnett. The show features a panel of potential venture capital investors, called "sharks", that. I have also included a few lifestyle strategies that may help you lose belly fat, which include adding fiber and probiotics to your diet, following a nutrient tracker. 25 Sexy Gifts That You’ll Enjoy As Much As She Does Get your wife or girlfriend something naughty this year By Sarah Jacobsson Purewal November 18, 2016. Time was, humans didn’t have to worry much about getting exercise. When we had to kill, gather, grow, or herd our own food, working out happened naturally. An estimated 1. 4 million workers in the U. S. No. matter what the noise problems may be in a particular workplace. It may be possible to: Use quieter work processes. Alter or enclose equipment to reduce noise at the source. Use sound- absorbing materials to prevent the spread of noise by. In the field of noise control, where there's a will, there's a way. The Occupational Safety and Health Administration (OSHA) was established. U. S. Congress to help eliminate job safety and health hazards such. This book is presented by OSHA for workers and employers interested in. OSHA believes that highly technical training is. Noise problems can often be solved by the workers and. The book contains five major sections. First, a brief overview of the effects of noise on human health. Second, a discussion of some of the key words and concepts. Third, an explanation of specific principles of noise control. Fourth, a discussion of particular techniques for controlling. Fifth, a description of the ways OSHA can help employers and employees. OSHA hopes that the information in this book will be discussed by. If more help is needed. OSHA area office listed in the back of the book. The ability to hear is one. Without it, it is very difficult to lead a. Excessive noise can destroy the ability to hear, and may. For most effects of noise, there is no cure, so. Hearing. The damage done by noise depends mainly on how loud it is. The frequency or pitch can also have some. After a period of time off, hearing may be restored. Some workers. who suffer temporary hearing loss may find that by the time their hearing. Permanent hearing loss results from the destruction of cells in. Such damage. can be cause by long- term exposure to loud noise or, in some cases, by. Normally, workplace noise first affects the ability to hear. This means that even though a person can still hear some. Workers with hearing impairment typically say . As conversation. becomes more difficult to understand, the person becomes isolated from. Over a long period of time. Noise may also put stress on other parts of the body by. Figure 1). Workers exposed to noise sometimes complain of nervousness. Excessive noise exposure also can reduce job. Figure 1. In addition to causing hearing loss by. Figure 2. Severe destruction of the hair cells in the. Top picture: normal hair cells, lower picture: hair cells. There are a number of words and concepts which must be. Sound. Sound is produced when a sound source sets the air nearest. The motion spreads to air particles far from the. Sound travels in air at a speed of about 3. The rate of travel is greater in liquids and solids; for example. Note: Measurements in this book are generally given in. To convert, one meter equals about 3. Frequency (Hz)The frequency of a sound wave refers to the number of. Hz). Sound is found. The sound source vibrates and affects air. Figure 4. A pure tone is marked by a single column. Musical notes. contain several tones of different frequencies and intensities. Hz and 2. 0,0. 00 Hz. The boundary between high and low frequencies is generally. Hz. Sound may consist of a single pure tone, but in general it. Noise. It is customary to call any undesirable sound . For example, higher frequencies are more. Pure tones are more disturbing than a sound made. Infrasound and ultrasound. Sound with frequencies below 2. Hz is called infrasound. Hz is called ultrasound. There is some. evidence that these sounds which cannot be heard can under certain. This book deals only with. Figure 5. Noise is a disorderly mixture of tones at. Figure 6. At the same intensity, the noise from a truck. Decibel (d. B)Sound levels are measured in units of decibels (d. B). If. sound is intensified by 1. B, it seems to the ears approximately as if. A reduction by 1. B makes it seem as if. Noise level measurement. In measuring sound levels, instruments are used which. The instruments measure the . A number of manuals for noise measurements are. Adding noise levels. Decibel levels for two or more sounds cannot simply be. Figure 8 shows how the combined effect of two sounds depends on the. Two or more sounds of the same level combine. Octave band. It is common practice to divide the range of frequencies we. The sound level is then listed for each. The top frequency in an octave band is always twice the. The octave band may be referred to by a center frequency. For. example, 5. 00 Hz is the center frequency for the octave band 3. Hz. A fan produces a sound level of 5. B(A). The difference is 6 d. B(A), and according to. B(A) will be added to the highest level. Operating. together, the fans will result in a level of 5. B(A). Sound transmission. The word . However, sound waves also travel in solids and liquids. The frequency. depends on the size and construction of the object or air volume. Sound reduction by distance. Sound spreading in open air and measured at a certain. B for each doubling of. Sound is reduced less when spreading inside a room. The. wall's ability to block transmission is indicated by its transmission loss. TL) rating, measured in decibels. The TL of a wall does not vary. Noise reduction (NR)Noise reduction is the number of decibels of sound. This can. be measured by comparing the noise level before and after installing an. NR and TL are not necessarily the same. Sound absorption. Sound is absorbed when it strikes a porous material. If a small sound source produces a sound. B at a distance of 1 meter, the sound level at a 2 meter. B, at 4 meters 7. B, etc. Figure 1. Part of the sound that strikes a wall is. The transmission. TL) of the wall is determined by the portion of the noise which is. The following section explains how to apply basic noise. In many cases, several principles must be applied and. Of course, these principles do not. The principles are discussed in eight sections: A. Sound from vibrating plates. C. Sound production in air or gases. D. Sound production in flowing liquids. E. Sound movement indoors. F. Sound movement in ducts. G. Sound from vibrating machines. H. Sound reduction in enclosure walls. A number of symbols are used throughout the drawings. For. example, large black arrows indicate strong sound radiation and smaller. CAUSES OF. SOUND PRODUCTION - A1. Changes in force, pressure, or speed. Sound is always produced by changes in force, pressure, or. Great changes produce louder noises and small changes quieter ones. Since the. cardboard strip continues to move, the knife must travel at an angle in. The cutting is practically noise. SOUND BEHAVIOR - CAUSES OF SOUND PRODUCTION - A2 Airborne sound is usually caused by. For example, vibrations of the strings in a musical. When the. sound box vibrates, sound is transmitted to the air. A circulation pump. The sound. waves are transmitted through the pipes to the radiators, whose large. Example. Turbulent fluid flow within pipes produces sound which can. Control measure. In addition to reducing the turbulence in the pipe, the. The vibrations can be. SOUND BEHAVIOR - CAUSES OF SOUND PRODUCTION - A3. Vibrations can produce sound after. Vibrations in solids and liquids can travel a great. Such vibrations can cause. The best solution is to stop the vibration. Principle. 16. Example. Vibrations from an elevator are transmitted throughout. Control measure. The elevator drive can be isolated from the building. SOUND BEHAVIOR - LOW AND HIGH FREQUENCIES - A4. The slower the repetition, the lower. The level of low frequency noise from a sound source is. The longer the time between changes, the lower the. The level of noise depends on the amount. Principle. 18. Example. Two gears have the same pitch diameter but different. If they rotate at the same speed, the gear with fewer. SOUND BEHAVIOR - LOW AND HIGH FREQUENCIES - A5. High frequency sound is strongly. When high frequency sound strikes a hard surface, it is. High frequency sound does not. Principle. 20. Example. High frequency noise travels directly from the. Control measure. A sound- insulating hood, open toward the bottom of the. The hood is coated on the inside. The upper portion of the opening is covered. As sound starts towards the ears, the glass reflects it. The sound level for the machine. SOUND BEHAVIOR - LOW AND HIGH FREQUENCIES - A6. Low frequency noise travels around. Low frequency noise radiates at approximately the same. It travels around corners and through holes, and. A shield has little effect. Principle. 22. Example. Compressors and the diesel engines inside them both may. Control measure. A complete enclosure of damped material lined with sound. The air and exhaust gases must pass through mufflers. Doors for. inspection must close tightly. SOUND BEHAVIOR - REDUCTION IN AIR - A7. High frequency sound is greatly. High frequency sound is reduced more effectively than low. In addition, it is easier to. If the noise source does not cause problems in its. Principle. 24. Example. The low frequency noise from roof fans in an industrial. Control measure. The rooftop fan is replaced by another one of similar. This produces less low. The low frequency noise no. SOUND BEHAVIOR - HOW DISTURBING? If it is not possible to reduce the noise, it may. Principle. 26. Example. The diesel engine in a ship operates at 1. The noise from the propeller is. Control measure. Differential gear is installed between the motor and. The propeller is. The noise is shifted to a lower frequency. SIZE AND THICKNESS - B1. Small vibrating surfaces give off less. An object with a small surface area may vibrate intensely. The higher the frequencies, the. Since machines always. Principle. 28. Example. Too much noise is radiated from the control panel of a. Control measure. The panel is detached from the system itself, the. SOUND FROM VIBRATING PLATES - SIZE AND THICKNESS - B2. Densely perforated plates produce less.
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