Technical Literature

Industrial Noise Series

Industrial Noise Series Part I: Fundamentals of Environmental Sound

Generally, if you can feel the effects of sound, then the levels are dangerously high and you are exposing yourself to harm. Studies have shown continuous long-term exposure to just 75 decibels (dB) can lead to hearing loss. Whenever working around a loud source of noise, wear hearing protection, even at home. The ear has a built-in mechanism to help protect it somewhat from high-amplitude sound, but not impact noise — too quick for the ear to respond. When exposed to high sound levels, the middle ear’s connecting tissues stiffen to reduce the effect to the inner ear and is why when you leave a noisy environment, your hearing threshold has shifted (everything sounds muffled).

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Industrial Noise Series Part II: Community & Environmental Noise

The environment is a dynamic place that is always in flux as caused by seasons of the year, weather, flora and fauna, and human factors such as communities, rail and road traffic, industries and businesses, aircraft and airports, and a host of similar activities including sporting events that all produce environmental noise. Making sound level measurements under such conditions can be challenging, and in order to convey the dynamics of the environment, a time-history sound survey measurement is necessary. Depending on why the measurement is being performed, it may be over a period of time that may extend from a few minutes to hours, days, or for three or four seasons of the year. What is important is to make sure the measurement conveys the necessary information of the environmental sound level in order to make decisions.

Download Now

Industrial Noise Series Part III: Near-Field Noise

The immediate area around equipment is called the near field. The near-field sound is of course the sound in that area; usually specified to be measured 3 feet or 1 meter from the equipment at 5 feet or 1.5 meters above grade (typical range of ear height). This also applies to structures and ducting to address breakout noise; that is, noise that comes through walls.

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Industrial Noise Series Part IV: Modeling Sound Propagation

A major challenge in acoustics is to accurately predict what the sound level will be at some location, far or near. Sound propagation modeling and prediction span from the simplest calculation to highly sophisticated computer programs. This treatise presents a basic overview of sound propagation that is typically performed for most industrial noise applications.

Download Now

Industrial Noise Series Part IX: Reactive Silencers

Reactive silencers are basically chamber and tube type units that may include some packing materials for middle and high frequency performance. These types of silencers are principally used on reciprocating engines (pistons) or other equipment having significant impulse type sound energy. The chamber and tubes are designed (tuned) to the principal impulsive frequencies that need to be attenuated. The attenuation is caused by the chambers and tubes that create internal reflective sound fields that reduce the sound energy. Because these units are tuned for each application, any changes will affect performance and includes connecting ducting, especially tail pipes.

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Industrial Noise Series Part V: Room Acoustics & Noise Control

Room acoustics describes the acoustics of an interior space and the transmission of noise from one space into another space and may include the noise that breaks out into the environment through the walls, windows, vents and roof. In most industrial applications, the concern is the breakout noise into the environment affecting the nearby community. In some cases, it is the interior sound level that is important in order to limit the occupant’s noise exposure or to ensure the sound level is low enough to allow ease of communications, especially in critical applications such as in control rooms. These industrial spaces are generally large enough to allow propagation of acoustic energy within the space. Small fitting enclosures over equipment are a special case and room acoustics is not an accurate method for analyzing those cases. The following sections are intended to present the basic concepts of room acoustics.

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Industrial Noise Series Part VI: Fundamentals of Noise Control

Noise control or mitigation involves several steps and the amount of noise reduction is driven by having to meet some regulatory limit.

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Industrial Noise Series Part VII: Silencers

The requirement for a silencer is generally developed by determining some amount of noise reduction needed to reduce noise emissions from some machine in order to meet a compliance requirement or environmental noise limit. Silencer performance may be specified using three parameters, noise reduction (NR), transmission loss (TL) and insertion loss (IL). In general, citing any of these three parameters will result in meeting the requirement; particularly, if it is to only meet an overall sound level reduction but there will be some variances in the very low frequencies that are discussed in following sections. 

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Industrial Noise Series Part VIII: Absorptive Silencer Design

The basics of absorptive silencer design and the fundamental approach in design of parallel baffle silencers is presented. The reduction of sound energy using absorptive materials is achieved by transferring the acoustical pressure (wave motion) into material motion. This mechanical motion is converted into heat (energy loss) by material damping and friction. The more effective the sound wave penetrates the material the more effective the attenuation. Each baffle assembly consists of “compartments” and the basic theory is each compartment is locally reacting where the acoustic sound wave “pumps in and out” though the material as well as through the perforated facing sheet or pack material retainer. The perforation pattern adds damping and frictional losses to the aero-acoustic wave oscillating through the holes; the smaller the holes and more perforations, the more attenuation. The packing consists of absorptive material that is principally fibrous materials or open cell foams that allow the wave energy to penetrate, induce material motion, and be attenuated.

Download Now

Industrial Noise Series Part X: OSHA

The near-field sound level limit is frequently invoked by citing OSHA as the authority for limiting the near-field sound level to either LA 85 or 90 decibels (dB). In the context of specifying a sound level, it is irrelevant to OSHA; it is concerned with occupational noise exposure, that is, the cumulative noise exposure that employees are exposed to as they perform their duties. OSHA does not impose a limiting sound level except for impulsive noise, where it is stated impulsive noise should not exceed 140 dB peak sound level. The sound level can be any level provided the employee does not exceed the allowable noise exposure limit; a function of the sound level and exposure time, not just the sound level.

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Silencing

ISOPE 2015 - Offshore Requirements for Turbine Exhaust Systems

Offshore combustion turbine exhaust systems are complex and are required to withstand the extreme environment and operating loads including high temperatures and gas flow. This paper presents a review of the design approaches and analysis process for development of an optimal silencer and duct system for a wide range of loading conditions including: internal pressure, environmental loads (wind, seismic, ice, etc.) and aero-acoustic performance. 

Download Now

ISOPE 2015 Presentation: Offshore Requirements for Turbine Exhaust Systems

This presentation was delivered to the ISOPE 2015 engineering conference attendees, based on the peer-reviewed paper, "Offshore Requirements for Turbine Exhaust System Analysis and Design." The ISOPE conferences and exhibitions provide an international forum where the engineers, managers and academia come each year to present and share new challenges and solutions in ocean, offshore and polar engineering. www.isope.org

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Technical Papers & Presentations

Analytical Processes for High-Performance Catalytic Exhaust Systems

Reciprocating engines continue to provide fuel efficient, clean and flexible motive power for many gas compression applications. While these engines are durable and flexible they create many challenges for the exhaust system designer. Compression stations that were originally built in isolated areas are now in or near neighborhoods, requiring greater focus on acoustic performance. New emission regulations now require catalyst systems on most all gas engines. These requirements have changed the design for a modern reciprocating engine exhaust system.

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Combined Cycle Systems

Power plants can be defined by functional type (e.g. base load, peak load, or combined cycle). Each has advantages and disadvantages. Base load power plants have the lowest operating cost and generate power most in any given year. There are several different types of base load power plants. The resources available typically determine the type of base load plant used to generate power. Coal and nuclear power plants are the primary types of base load power plants used in the Mid-West United States.

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Experience on Land

Experience on Land – What Have We Learned about System Integration from Land-Based SCR Systems?

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Health, Safety and Environmental Approach

Primary goals are to maintain “up-time” / equipment availability by managing equipment noise, reducing heat rejection, achieving low level of emissions output, protecting equipment and enabling efficient operation.

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Industrial Noise Series Part I: Fundamentals of Environmental Sound

Generally, if you can feel the effects of sound, then the levels are dangerously high and you are exposing yourself to harm. Studies have shown continuous long-term exposure to just 75 decibels (dB) can lead to hearing loss. Whenever working around a loud source of noise, wear hearing protection, even at home. The ear has a built-in mechanism to help protect it somewhat from high-amplitude sound, but not impact noise — too quick for the ear to respond. When exposed to high sound levels, the middle ear’s connecting tissues stiffen to reduce the effect to the inner ear and is why when you leave a noisy environment, your hearing threshold has shifted (everything sounds muffled).

Download Now

Industrial Noise Series Part II: Community & Environmental Noise

The environment is a dynamic place that is always in flux as caused by seasons of the year, weather, flora and fauna, and human factors such as communities, rail and road traffic, industries and businesses, aircraft and airports, and a host of similar activities including sporting events that all produce environmental noise. Making sound level measurements under such conditions can be challenging, and in order to convey the dynamics of the environment, a time-history sound survey measurement is necessary. Depending on why the measurement is being performed, it may be over a period of time that may extend from a few minutes to hours, days, or for three or four seasons of the year. What is important is to make sure the measurement conveys the necessary information of the environmental sound level in order to make decisions.

Download Now

Industrial Noise Series Part III: Near-Field Noise

The immediate area around equipment is called the near field. The near-field sound is of course the sound in that area; usually specified to be measured 3 feet or 1 meter from the equipment at 5 feet or 1.5 meters above grade (typical range of ear height). This also applies to structures and ducting to address breakout noise; that is, noise that comes through walls.

Download Now

Industrial Noise Series Part IV: Modeling Sound Propagation

A major challenge in acoustics is to accurately predict what the sound level will be at some location, far or near. Sound propagation modeling and prediction span from the simplest calculation to highly sophisticated computer programs. This treatise presents a basic overview of sound propagation that is typically performed for most industrial noise applications.

Download Now

Industrial Noise Series Part IX: Reactive Silencers

Reactive silencers are basically chamber and tube type units that may include some packing materials for middle and high frequency performance. These types of silencers are principally used on reciprocating engines (pistons) or other equipment having significant impulse type sound energy. The chamber and tubes are designed (tuned) to the principal impulsive frequencies that need to be attenuated. The attenuation is caused by the chambers and tubes that create internal reflective sound fields that reduce the sound energy. Because these units are tuned for each application, any changes will affect performance and includes connecting ducting, especially tail pipes.

Download Now

Industrial Noise Series Part V: Room Acoustics & Noise Control

Room acoustics describes the acoustics of an interior space and the transmission of noise from one space into another space and may include the noise that breaks out into the environment through the walls, windows, vents and roof. In most industrial applications, the concern is the breakout noise into the environment affecting the nearby community. In some cases, it is the interior sound level that is important in order to limit the occupant’s noise exposure or to ensure the sound level is low enough to allow ease of communications, especially in critical applications such as in control rooms. These industrial spaces are generally large enough to allow propagation of acoustic energy within the space. Small fitting enclosures over equipment are a special case and room acoustics is not an accurate method for analyzing those cases. The following sections are intended to present the basic concepts of room acoustics.

Download Now

Industrial Noise Series Part VI: Fundamentals of Noise Control

Noise control or mitigation involves several steps and the amount of noise reduction is driven by having to meet some regulatory limit.

Download Now

Industrial Noise Series Part VII: Silencers

The requirement for a silencer is generally developed by determining some amount of noise reduction needed to reduce noise emissions from some machine in order to meet a compliance requirement or environmental noise limit. Silencer performance may be specified using three parameters, noise reduction (NR), transmission loss (TL) and insertion loss (IL). In general, citing any of these three parameters will result in meeting the requirement; particularly, if it is to only meet an overall sound level reduction but there will be some variances in the very low frequencies that are discussed in following sections. 

Download Now

Industrial Noise Series Part VIII: Absorptive Silencer Design

The basics of absorptive silencer design and the fundamental approach in design of parallel baffle silencers is presented. The reduction of sound energy using absorptive materials is achieved by transferring the acoustical pressure (wave motion) into material motion. This mechanical motion is converted into heat (energy loss) by material damping and friction. The more effective the sound wave penetrates the material the more effective the attenuation. Each baffle assembly consists of “compartments” and the basic theory is each compartment is locally reacting where the acoustic sound wave “pumps in and out” though the material as well as through the perforated facing sheet or pack material retainer. The perforation pattern adds damping and frictional losses to the aero-acoustic wave oscillating through the holes; the smaller the holes and more perforations, the more attenuation. The packing consists of absorptive material that is principally fibrous materials or open cell foams that allow the wave energy to penetrate, induce material motion, and be attenuated.

Download Now

Industrial Noise Series Part X: OSHA

The near-field sound level limit is frequently invoked by citing OSHA as the authority for limiting the near-field sound level to either LA 85 or 90 decibels (dB). In the context of specifying a sound level, it is irrelevant to OSHA; it is concerned with occupational noise exposure, that is, the cumulative noise exposure that employees are exposed to as they perform their duties. OSHA does not impose a limiting sound level except for impulsive noise, where it is stated impulsive noise should not exceed 140 dB peak sound level. The sound level can be any level provided the employee does not exceed the allowable noise exposure limit; a function of the sound level and exposure time, not just the sound level.

Download Now

ISOPE 2015 - Offshore Requirements for Turbine Exhaust Systems

Offshore combustion turbine exhaust systems are complex and are required to withstand the extreme environment and operating loads including high temperatures and gas flow. This paper presents a review of the design approaches and analysis process for development of an optimal silencer and duct system for a wide range of loading conditions including: internal pressure, environmental loads (wind, seismic, ice, etc.) and aero-acoustic performance. 

Download Now

ISOPE 2015 Presentation: Offshore Requirements for Turbine Exhaust Systems

This presentation was delivered to the ISOPE 2015 engineering conference attendees, based on the peer-reviewed paper, "Offshore Requirements for Turbine Exhaust System Analysis and Design." The ISOPE conferences and exhibitions provide an international forum where the engineers, managers and academia come each year to present and share new challenges and solutions in ocean, offshore and polar engineering. www.isope.org

Download Now

Noise Sources and Solutions for Mobile Vacuum Trucks

Data are presented on the noise sources of mobile vacuum trucks as they are used as a stationary source, especially the rotary positive displacement blowers used to create the vacuum. These are straight lobe blowers manufactured by several companies. In addition to the expected intake and discharge noise, the bypass or jet port noise must be considered and may be the dominant noise source. Several solutions are discussed as well as limitations on space and weight. Once the blower noise is reduced, more traditional noise reduction of the engine, transmission and cooling fan noise must also be done.

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System Solutions for Optimizing Exhaust Emission Control Systems

There is a growing percentage of Decentralized Energy (DE) systems globally and with it comes an increased need to minimize the exhaust emissions produced by these sources. Modern exhaust emission control systems are very effective in reducing gaseous and particulate emissions when applied properly. However, competing system objectives such as cost, backpressure, packaging space, serviceability and noise control often present serious challenges to system designers. This paper provides a brief overview of the challenges associated with integrating exhaust emission control in reciprocating engine stationary power generation systems and offers potential system level solutions and design considerations for integration of efficient and cost-effective exhaust emission control systems.

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Total Solution

ISOPE 2015 - Offshore Requirements for Turbine Exhaust Systems

Offshore combustion turbine exhaust systems are complex and are required to withstand the extreme environment and operating loads including high temperatures and gas flow. This paper presents a review of the design approaches and analysis process for development of an optimal silencer and duct system for a wide range of loading conditions including: internal pressure, environmental loads (wind, seismic, ice, etc.) and aero-acoustic performance. 

Download Now

ISOPE 2015 Presentation: Offshore Requirements for Turbine Exhaust Systems

This presentation was delivered to the ISOPE 2015 engineering conference attendees, based on the peer-reviewed paper, "Offshore Requirements for Turbine Exhaust System Analysis and Design." The ISOPE conferences and exhibitions provide an international forum where the engineers, managers and academia come each year to present and share new challenges and solutions in ocean, offshore and polar engineering. www.isope.org

Download Now