Occupational Noise Program

This program outlines minimum global program requirements to protect Microsoft employees and external staff from hearing loss from exposure to elevated occupational noise levels. The primary goal of this Program is to lower, and ultimately prevent, hearing loss caused by workplace noise exposure. This is done by using facilities and equipment with practical protections built into their design. When effective engineering controls are not possible, or when they are being implemented, administrative controls will be applied when and where appropriate followed by using personal protective equipment (PPE).

Requirements outlined in this program are superseded by any applicable regulations. Such regulations may require additional measures (e.g. lower action levels) or prohibit specific listed requirements.

For employees with documented exposures above 85 dBA as an 8-hour time-weighted average (TWA), this Program provides information on required inclusion in the hearing conservation program.

NOTE: In all Microsoft work locations, hearing protection is required to be used any time the measured noise levels regularly meet or exceed 85 dBA, regardless of the duration of exposure.

The Occupational Noise Program is applicable to all Microsoft Full Time Employees (FTEs) and external staff directly supervised by Microsoft (as required by local regulations). Vendors/contractors not under the direct supervision of Microsoft FTEs must comply with applicable regulations and Microsoft procedures and controls while working at a Microsoft site. Vendors/contractors are responsible for evaluating and providing necessary controls for their employees.

3.1 Site Noise Control Plan

Each Microsoft location where noise levels are regularly measured above 80 dBA must have a Site Noise Control Plan (Plan) containing an up-to-date noise survey map and a Noise Monitoring Strategy. The Plan must be available for all employees, external staff, or regulatory agency personnel to review when requested. Noise surveys should be repeated at least every four years or whenever changes in conditions, equipment, or operations could significantly impact noise levels. Guidance for developing a Noise Monitoring Strategy can be found in Section 5.0 of this program.

Certain buildings may be required to observe local noise ordinances. Compliance with the local ordinances could restrict when certain activities may be performed. If applicable, these restrictions should be included in the Plan.

4.1 Occupational Noise Exposure and Thresholds for Action

A high-noise area is any area which routinely has measured noise levels at or above 85 dBA. Consideration must be given to both continuous and intermittent noise sources. The Site Administrator or lab manager with support from Microsoft OHS will evaluate noise levels or complete a risk assessment in areas where an employee or external staff may be exposed to noise levels equal to or exceeding 85 dBA.

Identified noise level thresholds that trigger specific activities to protect workers are:

* 8-hour TWA: 8-hour Time-Weighted Average

If local regulatory limits are more stringent than the limits above, the site must follow the applicable regulations and incorporate these regulations into a local noise procedure.

Most noise dosimeters account for exposure times less than or greater than 8 hours by calculating an 8-hour TWA. It is recommended that the 8-hour TWA reported by the dosimeter is compared to the applicable 8-hour Occupational Exposure Limit (OEL) for the purposes of evaluating and reporting personal noise exposure, including for the determination of inclusion in a hearing conservation program.

Noise assessments should be conducted in areas where employees report difficulties carrying on a normal conversation. Contact Global OHS to request assistance evaluating noise levels in the workplace.

4.2 Risk Assessment

A risk assessment will be performed using the existing risk assessment process (Risk Assessment Program) to assess occupational noise risks and to suggest mitigation controls. Recommended controls may include engineering controls, administrative controls, work practices, PPE, or corrective action items.

Assessment strategies could include:  

• Interviewing supervisors, employees, and external staff.  
• Observing work practices. 
• Reviewing supporting documents that may include applicable regulations and guidelines and SOPs.  
• Engaging process experts to review the tasks and develop safe work practices for operation and maintenance.  

Supervisors must notify the Plan Administrator when:

• Changes are made to job processes that present additional hazards. 
• Audit findings indicate noise levels that require further evaluation. 
• Employees express concerns about noise levels in the workplace. 

Data from risk assessments, employee, or external staff reports, or documentation such as equipment specifications, may indicate that potential elevated noise exposures may exist. For areas with potentially elevated noise levels, an area survey (noise map) should be created and made available for employees to review. Surveys must be repeated whenever conditions change that may significantly impact area noise levels. All proposed noise monitoring surveys must be entered into Enablon and peer-reviewed for quality assurance prior to initiating the project. 

• Noise monitoring strategies should be designed to: 
  • Characterize area noise levels by conducting noise monitoring
  • Identify high-noise areas requiring use of hearing protection 
  • Determine personal noise exposure levels for Similar Exposure Groups (SEGSs), if appropriate
  • Determine who may be subject to hearing conservation program requirements based on exposure 
  • Identify the proper type of noise controls or hearing protection
• Personal noise dosimetry will be performed:
  • To characterize noise levels for specific employees or SEGs depending on the nature of the exposure 
  • In response to employee concerns
  • When there is high worker mobility 
  • In areas with significant impulse noise or variations in sound levels, make area monitoring inappropriate

All noise surveys and personal dosimetry will be conducted by a qualified person (as defined by applicable local regulations). Noise monitoring strategies must be entered into Enablon, reviewed and approved by a designated regional competent person before sampling is initiated.   Participation in a personal dosimetry survey is optional for all employees and authorization from the employee is required before any samples are collected.

5.1 Equipment Calibration

All noise monitoring will be done using calibrated instrumentation consistent with the manufacturer’s instructions. Pre- and post-calibration procedures are extremely important because they confirm that the instrument is functioning properly on the day of use. Calibrations also confirm that changes in temperature or humidity have not affected the instrument's accuracy. If practical, spot check the instrument with a calibrator after the stabilization period.

Note: When unpacking a cold instrument in a warm environment, or moving from one temperature area to another, allow the instrument at least five minutes to stabilize for each 18°F (10°C) of change.

The general process for calibration is: 

• Setting up the instrument for use, taking it out of its case
• Turning on both the electronic “calibrator” and the noise-measuring instruments to allow them to “warm up”; see note above
• Checking the calibrator and instrument battery charge
• Testing the instruments with a standard tone of known pitch and intensity produced by the calibrator (e.g. 114 dB at 1,000 Hz)
• Checking the instrument reading during the test and making minor adjustments to the instrument if necessary
• Documenting the calibration results on the noise survey form  

For the post-use calibration check, the process is repeated, without making adjusts, after the instrument has been used. 

• Both the pre- and post-use calibration must be documented on the noise survey form

For areas with potentially elevated noise levels, an area survey (noise map) should be created and made available for employees to review. Surveys must be repeated whenever conditions change that may significantly impact area noise levels.

Area noise surveys are performed to assess and document the noise levels of a work area, identify areas requiring the use of hearing protection, sources of high noise including voluntary use, and are typically depicted on a noise map of the area. An area noise survey involves measuring noise levels at selected locations throughout an entire campus or sections of a room to identify noisy areas. Source surveys are performed to assess the noise levels associated with a piece of equipment or process, keeping in mind variability in noise levels during different operating conditions.

6.1 Noise Survey Procedure

Noise surveys should be repeated when there are significant changes to the space configurations, equipment, or operating procedures.  

• Results from these surveys are used to determine appropriate hearing protection and identify possible mitigation controls.  Obtain a plan of the work area to be assessed from MS Space, an evacuation map, or create a sketch of the area. 
• Document current conditions in the work area, including type and configuration of equipment, number of employees working there and amount of time per shift, and any other pertinent environmental conditions. Ensure the survey is conducted when conditions are representative of potential employee exposure(s). 
• Conduct the survey using a Sound Level Meter (SLM) that has been factory calibrated by the manufacturer within a year.  Retain calibration certificates. 
• Verify calibration using a sound calibrator immediately before and after the survey is completed. Document these results.

6.2 Sound Level Meter (SLM)

Using the SLM:

• Configure the SLM with the appropriate frequency weighting (typically A-weighted (dBA) for a general survey) and a response time (typically Slow for a general survey)  
• Record noise measurements at various locations around any noise-generating equipment. Ensure noise levels are collected in all areas where employees are working or could be working.  
• To take measurements, hold the SLM at arm’s length at ear height for employees exposed to noise, hold steady for about five seconds, and write the number down to the tenth place. If the noise level is highly variable, consider taking an integrated noise reading over a minute or longer. 
• Identify and document sample locations using a grid-like pattern, paying close attention to high levels of noise around equipment or employees. 
• Collect sufficient data to develop a comprehensive noise map. For equipment that generates noise levels greater than 85 dBA (or local action level if <85 dBA) slowly move away from the noise source until the SLM is reading <85 dBA. Take note of this distance away from the equipment on all sides, so the area(s) requiring hearing protection can be clearly delineated. 
• For equipment that generates noise levels greater than 100 dBA (or local double-hearing protection level if <100 dBA) slowly move away from the noise source until the SLM is reading 100 dBA. Take note of this distance away from the equipment on all sides, so the area(s) requiring double hearing protection can be clearly delineated. 

6.3 Documenting Noise Data

Document the following information in the noise survey, at a minimum:

• Name of the person conducting the survey
• Date and time of the survey (if done over multiple days, document all days)
• SLM model and serial number
• Pre-/post-calibration information including the calibrator serial number and calibration date 
• Location of the survey (building, room number(s), work areas, etc.)
• Operating conditions and any specific work tasks occurring during the survey
• Designated hearing protection areas
• Type of hearing protection available to employees for use  

Ask employees to describe operations, their work tasks, their workload, and time of day when work is the busiest. Other questions to ask employees to include in the noise report are:

• Briefly describe the workspace.
• Without divulging any confidential information, please explain the job tasks/equipment used during your shift?
• How long does the equipment/instrument run for?
• How many times does it run in a typical day?
• How long are you (the employee) in the workspace when the equipment/instrument is running?
• How long are your work shifts?
• Have you or any of your other coworkers experienced any symptoms of headaches, ringing in the ears (tinnitus), having difficulty hearing, and any work-related stress due to the loud environment or inability to hear your co-workers?

A noise map can be produced by drawing lines on the printout or sketch between points of equal sound level.

• Results and the area noise map should be included in the Area Noise Survey Report. This report must be uploaded into Enablon to document this sampling event along with a data download from the direct reading instrument(s) used in the survey.

The Area Noise Survey is the first step in a two-step process to assess the noise level an employee or a group of employees within a similar exposure Similar Exposure Group (SEG) are exposed to in their work environment. If the Area Noise Survey shows areas at or above the Microsoft Lower Action Level of 80 dBA and employees spend a significant period working in these locations, a personal noise monitoring survey (noise dosimetry) should be considered. It is not recommended to conduct personal dosimetry in areas where the average noise levels are less than 80 dBA, because speech can interfere with dosimetry results. Before using personal noise dosimeters, please read the corresponding manual for the dosimeters you will be using and if you have any questions, please contact Microsoft OHS.

7.1 Full-Shift Sampling Procedure

• Pre-calibrate noise dosimeters, sound level meters, and octave band analyzers; fully document calibration on noise survey form
• At the start of the agreed-upon time for sampling or immediately after a short opening discussion, place noise dosimeters on employees.
  • Explain to each employee being sampled who you are, why you are there, and the purpose of the dosimeter. Emphasize that the dosimeter is not a speech recording device.
  • Place the dosimeter on the employee’s lapel or pocket and position the microphone vertically on their shoulder facing upward, in the employee’s hearing zone.

• Once the dosimeter is placed ask the employee if it is comfortable and make sure it does not interfere with their work. 
  • Explain to the employee that you will check back regularly to ask the employee questions about their job tasks, their workload or check that the instrument is running correctly. 
  • Ask the employee to let you know right away if there is a problem with the dosimeter. For example, if a dosimeter is dropped in the field during testing make a note in the field notes and check the time on the report. 
  • Instruct the employee not to remove the dosimeter unless absolutely necessary, and not to cover the microphone with a coat or outer garment or move the microphone from its installed position.
  • Let the employee know if you will be collecting the dosimeter and pausing sampling during lunch. 
    • If the employee eats in their work area and lunch is part of the 8-hour work shift, you might consider leaving the dosimeter on during lunch.
• Record the time you turned on the noise dosimeter(s) on the noise survey form.
  
  

On the noise survey form document:

• Record necessary information about the worker: 
  • Job Title 
  • FTE or Vendor
  • Department
  • Job Description
  • Type of Hearing Protection Worn and Noise Reduction Rating (NRR)
  • Any Engineering or Administrative Controls in Use
  • Frequency and Duration of Noise Exposure
  • Source(s) of Noise (Instruments/Machines/Air Vents or Pumps, etc.) 

Make notes about the distance of the employee to the noise source, how the machine/instrument works, other employees passing through the work area, size and the shape of the room, where the noise source is positioned in the room and to other noise sources, what type of material is the floor, ceiling, and walls made of, who is wearing hearing protection, and if they are wearing hearing protection probably.

7.2 Extended Shift Sampling

After the 8-hour or extended shift:

• Stop the dosimeter and record the time on the noise survey form.
• Remove the dosimeter from the employee. 
• Post-calibrate the dosimeter and other noise equipment and document the calibration.
• Download the noise report and document the exposure.
• Write the results in the noise report (please see Appendix I: Area or Personal Noise Survey Report) and notify the employees.

All noise monitoring results (personal and area) must be communicated to the affected employees within 30 days of receipt of the finalized results. Once monitoring data has been entered into Enablon, use the program to generate employee notification letters.  

Employee notification letters must be peer-reviewed prior to being sent to the employee. Evidence the email was sent to the employee should uploaded into Enablon.

Once you have identified and measured the sources of the noise, identify appropriate controls considering the hierarchy of controls.  The best prevention strategy is to eliminate exposure to hazards that can lead to hearing loss. This document provides recommendations and information about potential controls and should not be considered an all-inclusive list; for questions or concerns please contact Global OHS. The hierarchy of controls for noise can be summarized as: 

• Eliminate or minimize noise exposure by installing or buying equipment that produces less noise (buy quiet programs) 
• Prevent or contain the escape of noise at its source (engineering controls)
• Control exposure by changing work schedules to reduce the amount of time any one worker spends in the high noise area (administrative controls)
• Change practices such as distancing from noise-producing equipment (work practice controls) 
• Control the exposure with hearing protection.

9.1 Elimination, Substitution, and Engineering Controls

All identified high noise generating operations or equipment must first be evaluated to determine if:

• The high-noise equipment or operation can be eliminated
• A piece of high-noise equipment can be substituted for a lower-noise generating alternative
• An engineering control can be implemented to lower noise generation 

Additional information about engineering controls can be found in Appendix B.

9.2 Administrative Controls

Administrative controls, defined as “changes in the work schedule or operations that reduce worker noise exposures,” may also effectively reduce noise exposure for employees. Administrative controls can include:

• Change of work methods
• Limiting time employees spend in the high noise area
• Worker rotation 

9.3 Personal Protective Equipment (PPE)

Hearing protection devices (HPDs) are a form of PPE and are the last line of defense for protecting workers from noise exposure(s). They may also be used in combination with engineering and administrative controls. HPDs come in a variety of sizes, shapes, and materials and can be reusable and/or disposable. Selected HPD must meet the appropriate performance standard (e.g. NRR, SNR, etc.) and provide adequate protection for the measured noise levels. All HPDs must have a minimum of 25 NRR or 28 SNR. The best hearing protector, when fitted correctly, is one that is accepted by the worker and worn properly.

• Double hearing protection is required in areas where noise levels exceed 95 dBA and placards or labels indicating that hearing protection is required must be posted in these areas. When delineating areas for double noise protection, consideration should be given to this distance away on all sides from the elevated source of noise.

Signage is required at the entrances to these areas to notify workers of this requirement prior to entry.

Work duration restrictions need to be evaluated and implemented when noise levels exceed 100 dBA.

For more information on Hearing Protection Devices please see Section 10.2.

Employees with a measured 8-hour TWA greater than 85 dBA, on any one day, must be included in a hearing conservation program. Microsoft OHS will notify Microsoft employees who fall into this category in writing.

• Hearing conservation program requirements include:  
  • Measuring noise levels in the workplace 
  • Baseline and annual audiometric tests for affected employees
  • Offering multiple styles of hearing protection at no cost to the employee
  • Initial and annual training
  • Notification to employees and external staff of any areas designated as high noise or requiring hearing protection 
• External staff will be notified of the high noise areas by the Lab or Facility Manager. 
• Lab Managers must make available multiple types or styles of hearing protection to accommodate the fit and comfort needs of individuals. and enforce the use of hearing protection by employees and external staff in high noise areas. 
• Signage must be posted in conspicuous locations stating that the use of hearing protection is required. 
• Areas where sound levels meet or exceed 95 dBA must have signs posted warning occupants of the high noise levels and double hearing protection requirements.

10.1 Audiometric Testing and Standard Threshold Shifts

Microsoft must ensure employees receive a baseline and an annual audiometric test if their exposure exceeds an 8-hour TWA of 85 dBA, on any one day.

• A baseline audiogram must be conducted within six months of initial exposure equal to or exceeding 85 dBA as an 8-hour TWA.  
  • Audiometric tests must be performed by a licensed or certified audiometric test technician. 
• Annual retesting is required if an employee continues to be routinely exposed to an 8-hour TWA of 85 dBA or more.   
  • Retesting should include a comparison of an employee’s baseline audiogram with the retest results to determine if a Standard Threshold Shift (STS) has occurred.   
• If an STS is indicated, the employee will be notified in writing within 21 days from the time the test was conducted.   
• The following steps will be taken with individual employees when an STS occurs:
  • The employee will be retested within 30 days of the original test.  
  • Medical referrals will be provided to the employee as directed by the audiometric professional evaluating the audiogram. 
  • Employees not using hearing protection will be fitted with hearing protection of appropriate attenuation, trained in the care, and required to use the hearing protection selected. 
  • Employees already using hearing protection will be refitted and retrained in the use of hearing protection and provided with hearing protection offering greater attenuation, if necessary. 
  • The annual audiogram will be substituted for the baseline audiogram if the STS is persistent, or the annual audiogram shows significant improvement over the baseline.   

10.2 Hearing Protection Devices

Hearing protection is required and should be enforced by the Lab, Facility, or Project Manager for those exposed to noise levels equal to or greater 85 dBA. This level defines the use of hearing protection regardless of the duration of exposure.

• All equipment and work areas identified at 85 dBA or above must have placards or labels indicating that hearing protection is required. 
• The selection of hearing protection must be adequate to reduce employee exposure to below 85 dBA and must be approved by NIOSH.  
• The type of hearing protection provided will depend on the noise exposure, the NRR of the hearing protection provided, and employee preference related to comfort and fit.  
• Ear buds or headphones used to listen to a personal music device are not hearing protection and should not be used as a substitute for approved hearing protection. 

10.3 Noise-Cancelling Devices

Noise cancellation is not equivalent to noise attenuation. All noise-cancellation devices must have an appropriate noise-reduction level (e.g. NRR, SNR, SLC80, etc.) if the device will be used as hearing protection. In addition, all electronic hearing protection devices (e.g. Bluetooth devices) must limit the noise output to 85 dBA or below.

Hearing protection requirements based on dBA levels measured by a SLM.

*Hearing protectors must attenuate employee exposure at least to an 8-hour time-weighted average of 85 decibels as required. See Appendix C. 

For more information on how to correctly wear earplugs and earmuffs, see Appendix E and Appendix F, respectively. For additional information on PPE selection, please refer to the Microsoft Personal Protective Equipment Program.

10.4 Training

Each Site must determine which employees are required to be included in the Hearing Conservation Program. Lab or Facility Managers must ensure external staff have been provided with site-specific information. For employees working in areas with documented elevated noise levels, training must be provided for: 

• Authorized personnel and defined external staff at initial assignment and annually thereafter 
• Retraining for employees and external staff as changes in procedures or work assignments occur  

Microsoft OHS has produced a training package to meet regulatory and company requirements for noise exposure. To obtain training, contact Global OHS . The training must be tailored to meet site-specific situations.  

The training program must include the following information: 

• Applicable federal, state, or local regulations
• Summary of the Noise Control Program and how to access the Site Plan
• Identification of affected job descriptions
• Effects of noise on hearing loss
• Purpose of the hearing protection 
• Advantages and disadvantages of various types of hearing protection
• Proper, selection, use, fit, and care of hearing protectors 
• Purpose and procedures for audiometric testing
• Procedures for responding to and reporting an incident

Upon completion of the training, employees must use and understand proper use of hearing protection, report concerns of elevated noise levels to Supervisors/Managers, and participate in annual noise training.

Individual employee records must be made available to the employee upon request.

The following terms are used in this document. The definitions below are used in the scope of this document, but local regulatory definitions supersede if there is a conflict.

Action Level: Noise level at which specific actions must be taken to control noise exposure in the workplace. Action levels may vary by regulatory jurisdiction. 

Administrative Controls: The use of employee training, job or task rotation, safe work practices, exposure monitoring, or medical surveillance to protect workers from exposures to workplace hazards.

Area Noise Survey: Area noise surveys are performed periodically to assess and document the overall noise levels of the work area, identify areas requiring the use of hearing protection, and are often documented via a noise map of a site. 

Audiometric Testing: Measurement of an individual’s ability to detect sounds, over a set of standardized frequencies. Such testing generally starts with baseline measurements, and is then repeated annually, to detect changes in hearing over time.

Criterion Level: The continuous equivalent 8-hour A-weighted sound level (as dBA) that constitutes 100% of an allowable noise exposure (dose)—in other words, the permissible exposure limit (PEL). 

Decibels (dB): A dimensionless unit commonly used to describe sound level intensity and hearing thresholds. 

dBA: Decibel scale modified by an A-weighted system. In the A-weighted system, the decibel values of sounds at low frequencies are adjusted. This adjustment accounts for the relative insensitivity of the human ear at low audio frequencies, especially below 1000 Hz.

Dose (%): Related to the criterion level, a dose reading of 100% is the maximum allowable exposure to accumulated noise. For OSHA, 100% dose occurs for an average sound level of 90 dB over an 8-hour period (or an equivalent exposure). If a TWA reading is used rather than the average sound level, the time period is no longer explicitly needed. A TWA of 90 dB is the equivalent of 100% dose. The dose doubles every time the TWA increases by the exchange rate. 

Engineering Controls: The elimination or reduction of a hazard by means of engineered machinery or equipment. Examples include process change, isolation, ventilation, and source modification.

Hearing Conservation Program: Standards and procedures to reduce the risk for noise-induced hearing loss in the workplace. Elements include noise monitoring, noise controls, audiometric evaluation, and training. Employees with a measured 8-hour TWA greater than 85 dBA, on any one day, must be included in a hearing conservation program.

Hearing Protection: Ear plugs or earmuffs worn by individuals to reduce sound exposures, before the implementation of engineering and administrative controls, or when such controls are not feasible.

High-Noise Area: An area that regularly has a noise level at or above 85 dBA.

Noise Dosimeter: A type of sound level meter that measures the dose of noise. This instrument can calculate the daily noise dose based on a full work shift of measurements, or a dose from a shorter sample. The operator can select different noise dose criteria, exchange rates, and thresholds.

Noise Reduction Rating (NRR): A numerical average attenuation provided by hearing protection devices. The higher the NRR, the greater the sound attenuation provided by the device, which reduces overall noise exposures for an individual.  

Occupational Exposure Limit (OEL): The maximum allowable noise level that an employee may be exposed to in the workplace for a given exposure time. 

Personal Noise Monitoring (Dosimetry): Monitoring of an employee’s workplace noise exposure throughout the duration of their work shift using a personal noise dosimeter. 

Risk Assessment: The process of quantifying the probability and severity of a harmful effect to individuals or populations from certain human activities.

Sound level meter: An instrument that converts sound pressure in air into corresponding electronic signals. The signals may be filtered to correspond to certain sound weightings (e.g. A-weighted scale, C-weighted scale).

Standard Threshold Shift (STS): A change of 10 dB or more in the average of hearing thresholds at testing frequencies of 2,000, 3,000, and 4,000 Hertz in either ear. The change is determined by comparing the current audiogram to a baseline audiogram. An STS may be temporary or permanent. A permanent STS requires specific follow-up actions by an employer within specific time frames. 

Time-Weighted Average (TWA): Average exposure for an individual over a specified working period, as determined by sampling at given times during the period. The most frequently used exposure guideline term is the average concentration over an 8-hour workday. 

Type 1/Type 2 (or Class 1 and Class 2): Two different accuracy specifications for noise measurements. Type 1 measurements are accurate to approximately ±1dB, and Type 2 measurements are accurate to approximately ±2dB. The accuracy of the measurements varies, however, depending on the frequency of the sound being measured. 

14.1 Microsoft Internal

• Microsoft Vendor Code of Conduct
  
• MS Policy 37019-2, Regulatory Compliance
• MS Policy 37019-5, Regulatory Investigations, Inspections, and Inquiries  
• Medical Surveillance Procedure
• Employee Safety Incident Reporting and Investigation Procedure
• Personal Protective Equipment Program

14.2 Microsoft External

• OSHA, 29 CFR 1910.95, Occupational Noise Exposure
• Washington, WAC 296-817, Hearing Loss Prevention (Noise)
• California, 8 CCR 5095-5099, Control of Noise Exposure
• NIOSH, Occupational Noise Exposure, DHHS (NIOSH) Publication Number 98-126
• ASTM, ASTM E1686-10 Standard Guide for Applying Environmental Noise Measurement Methods and Criteria
• European Directive: Consolidated TEXT: 32003L0010 — EN — 26.07.2019 (europa.eu)

Microsoft managers may use this outline to produce a written Site-Specific Noise Control Plan (Site Plan) for machines, equipment, processes, or areas under their control. The Site Plan must be tailored to identify or comply with the following: 

• Federal, state, or local regulations governing noise at the facility location
• Machines, equipment, or processes covered under their program
• Employees or contingent staff covered under their program

Managers must make the Site Plan available to employees, external staff, and corporate or regulatory compliance officers.    

Purpose

State the purpose of the plan (ensure that personnel are protected from occupational noise exposure).  

Scope

Describe the area or facility-specific operations that fall under this plan (when a risk assessment is performed and shows that noise levels meet or exceed 85 dBA).  

Regulations

A list of any applicable federal, state, and local regulations must be included here. For example, in the United States, federal regulations for Noise fall under OSHA, 29 CFR 1910.95, and Occupational Noise Exposure. However, individual states or local municipalities may have additional requirements.  

Roles and Responsibilities

Personnel with responsibility for oversight or implementation of the Site Plan must be identified here. This list need not include the names of specific individuals, but a specific job title and a summary of their role and area of responsibility must be included.  

Definitions

The written Site Plan must include definitions. However, additional definitions may be required based on applicable regulations, or activities that take place at the site.  

Workplace Survey and Risk Assessment

Summarize the workplace survey and risk assessments at the workplace. This summary can be presented as a table for easy reference.  Be sure that the summary allows the reader to easily identify the referenced machine, equipment, or process on the workplace floor. This can be done by including photographs or floor maps in the document.

PPE Procedures

This section must include the rules or requirements for implementation of the Site Plan. This section must describe specific procedures applicable to the need to reduce occupational noise.

Examples of items that need to be outlined in this section may include: 

1. Specific tasks that meet or exceed 85 dBA 
2. Specific areas that meet or exceed 85 dBA
3. Specific tasks and areas that require the use of hearing protection 
4. The location of hearing protection and instructions on how to use hearing protection
5. Engineering or administrative controls to reduce or eliminate the need for hearing protection 
6. Personnel roles and responsibilities
7. Completed risk assessments, exposure assessments, audiometric tests, and noise maps  

Training

Information on training frequency and site-specific training content must be incorporated in this section. 

Inspections

Annual inspections of the effectiveness of the Noise Control Program must be part of the Site Plan. Inspection documentation must be retained onsite. Following the inspection, training and other corrective actions must be taken as necessary.  

Incident Investigations

Incident investigations for all accidents, incidents, and near misses that were directly or indirectly related to noise must be documented in Enablon. Incidents inspection must be conducted by trained investigators following defined investigation methodology. Findings from the investigation should summarize the key points and corrective actions of those incidents that were directly or indirectly related to noise exposure.

Source

Source modification addresses the root cause of a noise problem. Reducing noise at the source is the best long-term noise control measure. At least four methods exist for treating the source: modification, retrofit, substitution, and relocation. 

Modification

Occupational noise can be produced by mechanical impacts, high-velocity fluid flow, high-velocity air flow, vibrating surface areas of a machine, etc., and at times by the product being manufactured.

Mechanical Impacts

To reduce noise caused by mechanical impacts, the modifications outlined below should be considered:

• Reduce excessive power or energy of items in motion (driving forces).
• Reduce or optimize speed.
• Minimize distance between impacting parts.
• Dynamically balance rotating equipment. 

High-Velocity Fluid Flow

High-velocity fluid flow can often create excessive noise as the transported medium passes through control valves or simply passes through the piping. Some effective modifications for high-velocity fluid-flow noise include:

• Locate control valves in straight runs of pipe.
• Locate all L’s and T’s at least 10 pipe diameters downstream of a valve.
• Ensure that all pipe cross-section reducers and expanders are at an included angle of 15 to 20 degrees.
• Eliminate sudden changes of direction and influx of one stream into another.
• Limit the fluid-flow velocity to a maximum of 30 feet per second for liquids.
• Maintain laminar flow for liquids (keep the Reynolds Number less than 2,000).
• When vibratory energy is transferred to the pipe wall, use flex connectors and/or vibration isolation for the piping system and/or acoustical insulation.
• When excessive noise in the fluid cannot be controlled by any of the options above, install an in-line silencer. 

High-Velocity Air Flow (Pneumatic or Compressed Air Systems)

One of the most common noise sources are pneumatic- or compressed-air-driven devices such as air valves, cylinders, and solenoid valves. As a source-modification, it is recommended that the air-pressure setting for all pneumatic devices be reduced or optimized to as low a value as practical. A general rule of thumb is that the sound pressure level can be reduced by approximately 6 dBA for each 30% reduction in air velocity.

Surface- or Panel-Radiated Noise

Machine casings or panels can be a source of noise when sufficient vibratory energy is transferred into the metal structure and the panel is an efficient radiator of sound. Conducting a thorough noise-control survey will help identify the source of vibration and the existence of any surface-radiated sound. The following noise-control measures should be considered: 

• Divide vibrating surface areas into smaller sections.
• Add stiffeners to large unsupported metal panels such as rectangular ducts or large machine casing sections.
• Add small openings or perforations to large, solid surfaces.
• Add vibration damping material. 

Retrofit

There are many commercially available acoustical products and applications that can be applied on or relatively close to the noise source(s) to minimize noise. Remember materials used to retrofit the source of the noise should not add to other hazards, for example be made of flammable material or be cumbersome. Specific retrofit materials and/or applications include the following:

Vibration Damping

Vibration damping materials can be an effective retrofit for controlling resonant tones radiated by vibrating metal panels or surface areas. The two basic damping applications are free-layer and constrained-layer damping. For damping materials to be successful, at a minimum, the two following conditions must be satisfied: 

• The panel being treated must be capable of creating high noise levels in the first place.
• The structure must be vibrating at one of its natural frequencies or normal modes of vibration. 

Some common applications for vibration damping include:

• Hopper bins and product chutes
• Thin metal machine casings or panels that radiate resonant tones
• Metal panels being impacted by production parts (e.g. drop bins)
• Metal enclosure walls
• Fan and blower housings
• Gear box casings

Vibration Isolation

Most industrial equipment vibrates to some extent. Isolators come in the form of metal springs, elastomeric mounts, and resilient pads. Some common applications for vibration isolation are: 

• Pipe hangers
• Heating, ventilation, and air conditioning (HVAC) equipment
• Flex connectors for piping systems
• Rotating machinery mounts and bases for electric motors, compressors, turbines, fans, pumps, and other similar equipment
• Impact equipment such as punch presses, forging hammers or hammer mills, and shearing presses
• Enclosure isolation

Silencers

Silencers are devices inserted in the path of a flowing medium, such as a pipeline or duct, to reduce the downstream sound level. The most common medium is air. There are basically four types of silencers:

• Dissipative (absorptive)
• Reactive (reflective)
• Combination of dissipative and reactive
• Pneumatic or compressed air devices 

Substitute

Often, equipment manufacturers have alternative devices that perform the same function at lower noise levels. These quieter devices typically cost more. When applicable, it will be necessary for the business group to determine if the noise-reduction benefit justifies the additional cost. Examples of alternative and quieter equipment may include:

• Gears
• Bearings
• Fans or blowers
• Control valves
• Air compressors
• Conveyors
• Electric motors
• Pumps

There might also be opportunities to replace equipment with different devices or materials. Where practical, examples of source substitution include: 

• Using belt drives over gears.
• Using belt conveyors instead of rollers.
• Employing mechanical parts ejectors or pickups over compressed air.
• Substituting quiet air nozzles for open-ended pipe or air lines.
• Replacing omnidirectional fans on electric motors with unidirectional aerodynamic fans.
• Substituting metal or steel parts with materials having high internal-damping properties, such as wood, nylon, or stiff plastic components.
• Using perforated or mesh panels in place of solid panels. 

Relocation

Controlling noise by locating or relocating the source should be considered for the design and equipment layout of new areas or and for reconfiguring existing areas. A simple rule to follow is to keep machines, processes, and work areas of approximately equal noise level together, and separate particularly noisy and quiet areas by buffer zones having intermediate noise levels. In addition, a single noisy machine should not be placed in a relatively quiet, populated area. Reasonable attention to equipment layout from an acoustical standpoint will not eliminate all noise problems, but it will help minimize the overall background noise level and provide more favorable working conditions.

Sound Transmission

After all available options for controlling noise at the source have been considered, the next step in the noise-control hierarchy is to determine ways to treat the sound transmission path. Common controls for the sound transmission path are:

• Adding sound-absorption materials to the room or equipment surfaces
• Installing sound transmission loss materials
• Using acoustical enclosures or barriers
• Any combination of these treatments

Use the following table to determine if hearing protection is adequate for the documented noise exposure.

Example:

An employee is exposed to noise levels averaging 95 db. The employee is wearing hearing protection with an NRR of 28  

28 - 7 = 21 

21/2 = 10.5 (round up to 11) 

95 - 11 = 84 dB 

In this example, the hearing protection is adequate for the given noise level provided it is fitted correctly and is used.

Use of Double Hearing Protection

Use of double hearing protection may be required when the single set does not provide sufficient protective. When noise levels exceed 100 dB and there are no feasible engineering controls to reduce noise, double hearing protection is required. In most situations, earmuffs are used over inserted ear plugs.  

Example:

The average noise exposure measured is 99 dB. The employee is wearing earplugs with an NRR of 29 and earmuffs with an NRR of 25.  

29 - 7 = 22 

22/2 = 11 

11 + 5 = 16 

99 - 16 = 83 dB 

In this example, the combination of hearing protection is adequate for the given noise level provided it is fitted correctly and is used.

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