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1.Ergonomic Aspects of Noise
2.Sound & Noise
Sound is a disturbance that propagates through a medium having properties of inertia ( mass ) and elasticity. The medium by which the audible waves are transmitted is air.
Sound is a disturbance that propagates through a medium having properties of inertia ( mass ) and elasticity. The medium by which the audible waves are transmitted is air.
3.Noise exposure limits
OSHA( Occupational Safety & Health Administration ) has established permissible noise exposures for persons working on jobs in industry.
Exposure to any sound level at or above 80 dBA causes the listener to incur a partial dose of noise. (Exposures to sound levels less than 80 dBA are ignored in calculating doses.)
OSHA( Occupational Safety & Health Administration ) has established permissible noise exposures for persons working on jobs in industry.
Exposure to any sound level at or above 80 dBA causes the listener to incur a partial dose of noise. (Exposures to sound levels less than 80 dBA are ignored in calculating doses.)
4.Sound Level Meter
Sound level meters measure sound pressure level and are commonly used in noise pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise.
Sound level meters measure sound pressure level and are commonly used in noise pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise.
5.Sound Level Meter Scales
Sound-pressure meters built to American National Standards Institute (ANSI) specifications contain frequency-response weighting networks (designated A. B, and C).
Each network electronically attenuates sounds of certain frequencies and produces a weighted total sound pressure level.
The Occupational Safety and Health Administration (OSHA) standards for daily occupational noise limits are specified in terms of this measure, and the Environmental Protection Agency (1974) has selected the A scale as the appropriate measure of environmental noise.
Many indices of loudness, noisiness, and annoyance are all based on the A scale (the unit is dBA).
Of the three scales, the A scale comes closest to approximating the response characteristics of the human ear.
Sound-pressure meters built to American National Standards Institute (ANSI) specifications contain frequency-response weighting networks (designated A. B, and C).
Each network electronically attenuates sounds of certain frequencies and produces a weighted total sound pressure level.
The Occupational Safety and Health Administration (OSHA) standards for daily occupational noise limits are specified in terms of this measure, and the Environmental Protection Agency (1974) has selected the A scale as the appropriate measure of environmental noise.
Many indices of loudness, noisiness, and annoyance are all based on the A scale (the unit is dBA).
Of the three scales, the A scale comes closest to approximating the response characteristics of the human ear.
6.Noise Dose
You are exposed to 3 noise sources during your work day.
4 hours at 90 dBA
2 hours at 95 dBA
.5 hours at 105 dBA
Your total noise dose is:
D = 100 x (4/8 + 2/4 + 0.5/1) = 150 %
Is your hearing at risk? Yes.
You are exposed to 3 noise sources during your work day.
4 hours at 90 dBA
2 hours at 95 dBA
.5 hours at 105 dBA
Your total noise dose is:
D = 100 x (4/8 + 2/4 + 0.5/1) = 150 %
Is your hearing at risk? Yes.
7.Measuring Sound/Noise
Noise levels are measured on a logarithmic scale by taking sound measurements (dB) and then applying a weighting factor to account for how loud/audible sound levels are to the human ear (dB(A)).
When calculating an individuals personal noise exposure there are different types of measurement that may be taken, which are recorded using a Sound Level Meter.
Leq Levels of equivalent noise in the work environment
Lep,d Personal daily noise exposure, usually calculated over 8 hours
Noise levels are measured on a logarithmic scale by taking sound measurements (dB) and then applying a weighting factor to account for how loud/audible sound levels are to the human ear (dB(A)).
When calculating an individuals personal noise exposure there are different types of measurement that may be taken, which are recorded using a Sound Level Meter.
Leq Levels of equivalent noise in the work environment
Lep,d Personal daily noise exposure, usually calculated over 8 hours
8.Psychophysical Indices
Robinson and Dadson (1957) presented to subjects a 1000-Hz pure tone (the reference sound) at different sound-pressure levels and had the subjects adjust the intensity of various frequency pure tones (the comparison sounds) until the comparison sound was judged to be of equal loudness to the reference sound.
The unit phon was designated as the measure of loudness and was set equal to the decibel level of the 1000-Hz tone.
Robinson and Dadson (1957) presented to subjects a 1000-Hz pure tone (the reference sound) at different sound-pressure levels and had the subjects adjust the intensity of various frequency pure tones (the comparison sounds) until the comparison sound was judged to be of equal loudness to the reference sound.
The unit phon was designated as the measure of loudness and was set equal to the decibel level of the 1000-Hz tone.
9.The phon tells us about the subjective equality of various sounds, but it tells us nothing about the relative loudness of different sounds. i.e., we cannot say how many times louder a 40-phon sound is compared to a 20-phon sound. For such comparative judgments we need still another yardstick.
Fletcher and Munson (1933) developed such a scale, and Stevens (1936) named it the sone.
10.Noise and loss of hearing
There are really two primary types of deafness:
Nerve deafness and
Conduction deafness.
Conduction deafness is caused by some condition of the outer or middle ear that affects the transmission of sound waves to the inner ear. It may be caused by different conditions, infection of the middle ear, wax or some other substance in the outer ear.
In nerve deafness, some defect in the sensory cells of the inner ear prevents transmission of sound impulses from the inner ear to the auditory centre in the brain. The damage from this type of defect is usually uneven and not a loss of all hearing. Those afflicted with this type of hearing loss, may loose sensitivity to different tones(usually the higher tones).
Fletcher and Munson (1933) developed such a scale, and Stevens (1936) named it the sone.
10.Noise and loss of hearing
There are really two primary types of deafness:
Nerve deafness and
Conduction deafness.
Conduction deafness is caused by some condition of the outer or middle ear that affects the transmission of sound waves to the inner ear. It may be caused by different conditions, infection of the middle ear, wax or some other substance in the outer ear.
In nerve deafness, some defect in the sensory cells of the inner ear prevents transmission of sound impulses from the inner ear to the auditory centre in the brain. The damage from this type of defect is usually uneven and not a loss of all hearing. Those afflicted with this type of hearing loss, may loose sensitivity to different tones(usually the higher tones).
11.Measuring Hearing
Audiometer is used to measure hearing.
An audiometer presents tones of various frequencies to the subject through an earphone. By varying the sound-pressure level of the tone, the minimum audible sound-pressure level (threshold) is determined for each frequency.
Audiometer is used to measure hearing.
An audiometer presents tones of various frequencies to the subject through an earphone. By varying the sound-pressure level of the tone, the minimum audible sound-pressure level (threshold) is determined for each frequency.
12.Normal Hearing and Hearing loss
Normal, non-occupational, hearing loss is considered to be due to two sources:
Presbycusis and
Sociocusis.
Presbycusis is hearing loss due to the normal process of aging.
Sociocusis refers to hearing loss due to non-occupational noise sources. such as household noises, television, radio, traffic, etc.
Normal, non-occupational, hearing loss is considered to be due to two sources:
Presbycusis and
Sociocusis.
Presbycusis is hearing loss due to the normal process of aging.
Sociocusis refers to hearing loss due to non-occupational noise sources. such as household noises, television, radio, traffic, etc.
13.Noise Induced Health Effects
Exposure to high or prolonged levels of noise can have both temporary and permanent effects on an individuals ability to hear, impacting not only on their personal lives, but also on their ability to hear warning signals at work.
Temporary Threshold Shift
Caused by a single, loud noise such as an explosion, gun shot or single impact (often causes temporary hearing loss).
Permanent Threshold Shift
Continuous, regular exposure to loud noise, such as machine, causing permanent hearing damage (Noise Induced Hearing Loss – NIHL)
Tinnitus
Ringing, whistling, buzzing sound in the ear, which is irreversible. This is a distressing condition, leading to lack of concentration and poor sleep.
Stress
Unwanted and irritating noise can increase stress levels creating safety hazards in that it interferes with potential warnings and communications.
Exposure to high or prolonged levels of noise can have both temporary and permanent effects on an individuals ability to hear, impacting not only on their personal lives, but also on their ability to hear warning signals at work.
Temporary Threshold Shift
Caused by a single, loud noise such as an explosion, gun shot or single impact (often causes temporary hearing loss).
Permanent Threshold Shift
Continuous, regular exposure to loud noise, such as machine, causing permanent hearing damage (Noise Induced Hearing Loss – NIHL)
Tinnitus
Ringing, whistling, buzzing sound in the ear, which is irreversible. This is a distressing condition, leading to lack of concentration and poor sleep.
Stress
Unwanted and irritating noise can increase stress levels creating safety hazards in that it interferes with potential warnings and communications.
14.Physiological effects of noise
The onset of a loud noise will cause a startle response, characterized by muscle contractions, blink, and head-jerk movement.
In addition, larger and slower breathing movements, small changes in heart rate, and dilation of the pupils occur. There is also a moderate reduction in the diameter of blood vessels in the peripheral regions, particularly the skin .
In residential communities, for example, high noise levels (e.g., aircraft noise) disrupt sleep, cause annoyance, and may cause concern for one's safety. adverse health effects associated with noise (such as hypertension, gastrointestinal problems. Telectrocardiograrn irregularities, and complaints of headaches) are usually evidenced only with relatively high levels of noise, often over 95 dBA.
The onset of a loud noise will cause a startle response, characterized by muscle contractions, blink, and head-jerk movement.
In addition, larger and slower breathing movements, small changes in heart rate, and dilation of the pupils occur. There is also a moderate reduction in the diameter of blood vessels in the peripheral regions, particularly the skin .
In residential communities, for example, high noise levels (e.g., aircraft noise) disrupt sleep, cause annoyance, and may cause concern for one's safety. adverse health effects associated with noise (such as hypertension, gastrointestinal problems. Telectrocardiograrn irregularities, and complaints of headaches) are usually evidenced only with relatively high levels of noise, often over 95 dBA.
15.Noise Controls
The HSE advocates a hierarchy of noise control measures. The hierarchy determined the methods of control that should be considered and in what order.
Noise Control Measures:
Control Noise at Source
Substitution
Isolation / Pathway interruption
Distance
Hearing Protection – the last resort !
The HSE advocates a hierarchy of noise control measures. The hierarchy determined the methods of control that should be considered and in what order.
Noise Control Measures:
Control Noise at Source
Substitution
Isolation / Pathway interruption
Distance
Hearing Protection – the last resort !
16.
Controlling Noise at Source
The Best method of prevention is to eliminate the hazard. Therefore controlling noise at its source is the best method of noise control.
Noise control at the source can be engineered by:
Avoiding impacts between machine parts;
Increasing the rigidity of containers receiving impact from goods, or damping them with damping materials;
Surface Coatings – sound absorption materials;
Dynamic balancing of rotating parts – reduce vibration;
Enclosing particularly noisy machine parts;
Providing mufflers for the air outlets of pneumatic valves;
Providing mufflers for electric motors;
Providing mufflers for intakes of air compressors.
Reducing the dropping height of goods being collected in bins and boxes;
Controlling Noise at Source
The Best method of prevention is to eliminate the hazard. Therefore controlling noise at its source is the best method of noise control.
Noise control at the source can be engineered by:
Avoiding impacts between machine parts;
Increasing the rigidity of containers receiving impact from goods, or damping them with damping materials;
Surface Coatings – sound absorption materials;
Dynamic balancing of rotating parts – reduce vibration;
Enclosing particularly noisy machine parts;
Providing mufflers for the air outlets of pneumatic valves;
Providing mufflers for electric motors;
Providing mufflers for intakes of air compressors.
Reducing the dropping height of goods being collected in bins and boxes;
17.Substitution
Substituting a process for one that is quieter, or altering existing processes
Shearing is quieter than stamping
Replacing metal parts with quieter hard plastic parts;
Changing to quieter types of fans or placing mufflers in the ducts of ventilation systems;
Using belt conveyors rather than the roller type.
Hydraulic drivers and quieter than pneumatic
Break stem rivets instead of hammered
18.
Isolation / Pathway interruption
If it is not possible to control the noise at the source, then it may be necessary to enclose the machine, place sound-reducing barriers between the source and the worker, or increase the distance between the worker and the source.
Few points to remember when controlling noise with barriers:
An enclosure should not be in contact with any part of the machine;
Holes in the enclosure should be minimized;
Access doors and holes for wiring and piping should be fitted with rubber gaskets;
Panels of insulating enclosures must be covered inside with sound-absorbent material;
Noise source should be separated from other work areas;
Sound-absorbent materials should be used, if possible, on walls, floors and ceilings.
Substituting a process for one that is quieter, or altering existing processes
Shearing is quieter than stamping
Replacing metal parts with quieter hard plastic parts;
Changing to quieter types of fans or placing mufflers in the ducts of ventilation systems;
Using belt conveyors rather than the roller type.
Hydraulic drivers and quieter than pneumatic
Break stem rivets instead of hammered
18.
Isolation / Pathway interruption
If it is not possible to control the noise at the source, then it may be necessary to enclose the machine, place sound-reducing barriers between the source and the worker, or increase the distance between the worker and the source.
Few points to remember when controlling noise with barriers:
An enclosure should not be in contact with any part of the machine;
Holes in the enclosure should be minimized;
Access doors and holes for wiring and piping should be fitted with rubber gaskets;
Panels of insulating enclosures must be covered inside with sound-absorbent material;
Noise source should be separated from other work areas;
Sound-absorbent materials should be used, if possible, on walls, floors and ceilings.
19.Isolation between noise & worker can be achieved by:
Acoustic enclosures – surrounding machine/process;
Acoustic shielding – partial enclosures;
Absorbing panels – interrupts noise path;
Noise refuges – noise free enclosure/booth from which operators work;
Noise should be deflected away from work areas with a sound-insulating or reflecting barrier.
Acoustic enclosures – surrounding machine/process;
Acoustic shielding – partial enclosures;
Absorbing panels – interrupts noise path;
Noise refuges – noise free enclosure/booth from which operators work;
Noise should be deflected away from work areas with a sound-insulating or reflecting barrier.
20.Hearing Protection
Forcing the worker to adapt to the workplace is always the least desirable form of protection from any hazard. As with all types of PPE(personal protective equipment), hearing protection should be used as the last form of defence once all other control methods have been utilised.
There are 2 main types of hearing protection: Both are designed to prevent excessive noise from reaching the inner ear.
Forcing the worker to adapt to the workplace is always the least desirable form of protection from any hazard. As with all types of PPE(personal protective equipment), hearing protection should be used as the last form of defence once all other control methods have been utilised.
There are 2 main types of hearing protection: Both are designed to prevent excessive noise from reaching the inner ear.
21.Ear protection is the least acceptable method of controlling an occupational noise problem because:
The noise is still present: it has not been reduced;
In hot, humid conditions workers often prefer earplugs (which are less effective) because earmuffs make the ears sweaty and uncomfortable;
Workers cannot communicate with each other and cannot hear warning signals;
Management does not always provide the correct type of ear protection: often it is a case of “the cheaper the better”;
If ear protection is provided instead of controlling the noise at source, then management is putting the responsibility on the worker — it becomes the worker's fault if he or she becomes deaf.
The noise is still present: it has not been reduced;
In hot, humid conditions workers often prefer earplugs (which are less effective) because earmuffs make the ears sweaty and uncomfortable;
Workers cannot communicate with each other and cannot hear warning signals;
Management does not always provide the correct type of ear protection: often it is a case of “the cheaper the better”;
If ear protection is provided instead of controlling the noise at source, then management is putting the responsibility on the worker — it becomes the worker's fault if he or she becomes deaf.
22.Introduction & Objective
The causal relationship between work place noise and hearing loss has been observed for centuries. The problem of industrial noise had been aggravated by the use of high speed, high production machines in the industries. There has been a great concern about the magnitude of industrial noise exposure, particularly in textile industry. The studies conducted in various countries showed the elevated level of noise pollution & the related hazards.
The present study was, therefore, conducted as a part of a plan to study, in details, noise pollution in selected high risk Saudi Industries. The scope of this present study includes textile, carpet, printing, publishing and paper product industries in Jeddah, Saudi Arabia.
The specific objectives of the study may be listed as:
• To map noise levels in selected industrial premises belonging to the above
mentioned industries, and check compliance with the standards for industrial
noise exposure.
• To provide recommendations for noise reduction and health protection of employees.
The causal relationship between work place noise and hearing loss has been observed for centuries. The problem of industrial noise had been aggravated by the use of high speed, high production machines in the industries. There has been a great concern about the magnitude of industrial noise exposure, particularly in textile industry. The studies conducted in various countries showed the elevated level of noise pollution & the related hazards.
The present study was, therefore, conducted as a part of a plan to study, in details, noise pollution in selected high risk Saudi Industries. The scope of this present study includes textile, carpet, printing, publishing and paper product industries in Jeddah, Saudi Arabia.
The specific objectives of the study may be listed as:
• To map noise levels in selected industrial premises belonging to the above
mentioned industries, and check compliance with the standards for industrial
noise exposure.
• To provide recommendations for noise reduction and health protection of employees.
23.Methodology
Selection of Factories
A list of all factories in the following 5 categories of industries in Jeddah was obtained:
Textile industry (b) Carpets industry,
(c) General Printing industry (d) Publishing industry (e) Paper Products industry.
A stratified random sample of 20 factories, representing about 40% of the above industries, was selected.
These included 3 textile, 2 carpet weaving, 7 printing, 3 publishing and 5 paper products factories.
Selection of Factories
A list of all factories in the following 5 categories of industries in Jeddah was obtained:
Textile industry (b) Carpets industry,
(c) General Printing industry (d) Publishing industry (e) Paper Products industry.
A stratified random sample of 20 factories, representing about 40% of the above industries, was selected.
These included 3 textile, 2 carpet weaving, 7 printing, 3 publishing and 5 paper products factories.
24.Noise Measurement
In individual factories, noise measurements were taken at strategic locations depending on the type, number and layout of machineries.
Other relevant data such as the operation, type and number of machinery, construction materials for roofs, floors, walls and ceilings etc. were also recorded.
The noise measurements included Leq (dBA), Maximum and Minimum SPLs at the individual octave bands.
Noise was measured using the B&K Sound Level Meter (SLM) type 2236.
An Omni-directional microphone type 4188 was used with the SLM.
The noise was measured at workers’ head level.
The calibration of the instrument was checked before and after each set of measurements.
The measurements were taken over a duration of 10 min at each location.
In individual factories, noise measurements were taken at strategic locations depending on the type, number and layout of machineries.
Other relevant data such as the operation, type and number of machinery, construction materials for roofs, floors, walls and ceilings etc. were also recorded.
The noise measurements included Leq (dBA), Maximum and Minimum SPLs at the individual octave bands.
Noise was measured using the B&K Sound Level Meter (SLM) type 2236.
An Omni-directional microphone type 4188 was used with the SLM.
The noise was measured at workers’ head level.
The calibration of the instrument was checked before and after each set of measurements.
The measurements were taken over a duration of 10 min at each location.
25.Analysis
The data were statistically analyzed using Excel.
For each factory, frequency tables for Leq, Max and Min SPLs were constructed.
This was followed by computing the mean dBA of Leq, Max and Min SPLs, and also at different octave bands, for individual factories.
The same analysis were done for each type of the industries by pooling the data of related factories.
The data were statistically analyzed using Excel.
For each factory, frequency tables for Leq, Max and Min SPLs were constructed.
This was followed by computing the mean dBA of Leq, Max and Min SPLs, and also at different octave bands, for individual factories.
The same analysis were done for each type of the industries by pooling the data of related factories.
26.Results and Discussion
Almost all the industries, at some instant are exceeding the acceptable safe noise level of 85 dBA.
In 45% industries, Leq is above 85dBA.
In 95% industries, max. SPL exceeds 85 dBA.
The most used and possibly, the most meaningful parameter, the Leq has varying degree of variance, ranging from 1.5 dBA (Hygienic Paper Products Co.) to 5.9 dBA (Nasr Printing Factory).
Factories with smaller variance of Leq could be treated with general noise control and reduction techniques. However, factories with high variation may have hot spots which would need individual noise control at the sources in addition to any general measures.
Noise levels over 85 dBA occur at frequencies mostly below 1 KHz across all industries. This indicates that noise reduction techniques when applied should take special care of frequencies below 1 KHz. Meanwhile, the reduction in noise at these frequency ranges will considerably reduce noise interference with workers’ speech, since much of the human speech is between 300 and 700 Hz.
Almost all the industries, at some instant are exceeding the acceptable safe noise level of 85 dBA.
In 45% industries, Leq is above 85dBA.
In 95% industries, max. SPL exceeds 85 dBA.
The most used and possibly, the most meaningful parameter, the Leq has varying degree of variance, ranging from 1.5 dBA (Hygienic Paper Products Co.) to 5.9 dBA (Nasr Printing Factory).
Factories with smaller variance of Leq could be treated with general noise control and reduction techniques. However, factories with high variation may have hot spots which would need individual noise control at the sources in addition to any general measures.
Noise levels over 85 dBA occur at frequencies mostly below 1 KHz across all industries. This indicates that noise reduction techniques when applied should take special care of frequencies below 1 KHz. Meanwhile, the reduction in noise at these frequency ranges will considerably reduce noise interference with workers’ speech, since much of the human speech is between 300 and 700 Hz.
27.Recommendations
Based on the analysis, the following recommendations may be considered to improve the overall situation:
Hot spots (i.e., sources that produce high noise levels) should be identified in individual factories, specifically, in publishing, paper products and textile industries.
As a first line of defense, noise control/reduction measures such as replacing or modifying noisy machines, better installation and maintenance of machines and where necessary, quarantining very noisy sources etc., should be adopted.
For the publishing and paper products industries, the situation seems critical. Noise reduction techniques such as redesigning walls and ceilings, using noise absorbing materials etc. should be adopted in addition to noise control measures suggested above.
In textile and printing industries, which are among the noisiest, it is not possible to isolate the machineries since the workers have to work close to the machines. Hence, in these industries, workers should have personal protection measures and should be rotated to reduce their exposure level.
Based on the analysis, the following recommendations may be considered to improve the overall situation:
Hot spots (i.e., sources that produce high noise levels) should be identified in individual factories, specifically, in publishing, paper products and textile industries.
As a first line of defense, noise control/reduction measures such as replacing or modifying noisy machines, better installation and maintenance of machines and where necessary, quarantining very noisy sources etc., should be adopted.
For the publishing and paper products industries, the situation seems critical. Noise reduction techniques such as redesigning walls and ceilings, using noise absorbing materials etc. should be adopted in addition to noise control measures suggested above.
In textile and printing industries, which are among the noisiest, it is not possible to isolate the machineries since the workers have to work close to the machines. Hence, in these industries, workers should have personal protection measures and should be rotated to reduce their exposure level.
28.
A general hearing conservation program to protect workers should be introduced in all these industries and more specifically in publishing, textile and paper products industries. Workers should have periodic audiometric tests to check the effectiveness of the noise controls and hearing conservation program.
A general policy to supply ear protectors regularly to all workers should be adopted (or even made compulsory) by all factories, since it is also very inexpensive.
The results of this study point to the need of further studies at the remaining factories belonging to these industries and the other industries as well.
A general hearing conservation program to protect workers should be introduced in all these industries and more specifically in publishing, textile and paper products industries. Workers should have periodic audiometric tests to check the effectiveness of the noise controls and hearing conservation program.
A general policy to supply ear protectors regularly to all workers should be adopted (or even made compulsory) by all factories, since it is also very inexpensive.
The results of this study point to the need of further studies at the remaining factories belonging to these industries and the other industries as well.
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