Noise Control in Industrial Equipment

Understanding Industrial Noise: Sources and Impacts

Industrial noise control represents one of the most critical yet often overlooked aspects of mechanical engineering in manufacturing and processing facilities. Across Nova Scotia and the broader Atlantic Canada region, industries ranging from fish processing plants to pulp and paper mills face ongoing challenges with equipment noise that affects worker safety, regulatory compliance, and community relations.

Excessive noise in industrial settings stems from numerous sources, each requiring specific analytical approaches and mitigation strategies. The primary contributors to industrial noise include:

• Rotating machinery – Motors, fans, pumps, and compressors generating continuous noise typically ranging from 85 to 110 dB(A)

• Impact processes – Stamping, forging, and pneumatic tools producing intermittent high-intensity noise often exceeding 120 dB(A)

• Fluid flow systems – Pipes, valves, and ducts creating turbulent flow noise and water hammer effects

• Combustion equipment – Boilers, furnaces, and generators contributing low-frequency rumble and exhaust noise

• Material handling – Conveyors, chutes, and hoppers generating structural vibration and impact noise

In Canada, the occupational exposure limit for noise is generally set at 85 dB(A) over an eight-hour time-weighted average, as specified by provincial workplace safety regulations including Nova Scotia's Workplace Health and Safety Regulations. Facilities exceeding these thresholds face not only regulatory penalties but also increased workers' compensation costs and potential hearing loss claims from employees.

Fundamental Principles of Noise Control Engineering

Effective noise control requires a systematic engineering approach that addresses the problem at its source whenever possible. The hierarchy of noise control follows three primary strategies, listed in order of preference and effectiveness:

Source Control

Addressing noise at its origin provides the most effective and economical long-term solution. Source control measures include selecting inherently quieter equipment during the design phase, maintaining equipment to prevent noise-generating wear patterns, and modifying operational parameters to reduce noise generation. For example, reducing fan speed by just 10% can decrease noise output by approximately 3 dB(A), while also reducing energy consumption significantly.

Modern variable frequency drives (VFDs) offer excellent opportunities for source control by allowing precise speed adjustment of motors and driven equipment. A centrifugal pump operating at 80% speed rather than full speed with throttling not only runs quieter but also consumes substantially less energy—a particularly relevant consideration for Maritime facilities facing high electricity costs.

Path Control

When source modification proves impractical or insufficient, controlling the transmission path between the noise source and receiver becomes essential. Path control strategies encompass barriers, enclosures, silencers, and vibration isolation systems. The effectiveness of these measures depends heavily on proper engineering analysis, including understanding the frequency characteristics of the noise and the acoustic properties of proposed solutions.

Sound transmission through solid structures often proves more problematic than airborne noise in industrial facilities. Vibration isolation using properly designed spring mounts, elastomeric pads, or inertia bases can reduce structure-borne noise by 20-30 dB when correctly specified. However, improper isolation can actually amplify noise at certain frequencies—a common mistake that underscores the importance of professional engineering analysis.

Receiver Protection

Personal protective equipment (PPE) such as earplugs and earmuffs represents the last line of defence when engineering controls cannot adequately reduce noise exposure. While necessary in many industrial environments, reliance on PPE alone indicates incomplete engineering solutions. Effective hearing protection programs require proper selection based on noise frequency characteristics, consistent worker compliance, and regular fit testing.

Acoustic Analysis and Measurement Techniques

Accurate noise assessment forms the foundation of any successful control programme. Professional acoustic analysis involves several measurement and analytical techniques that go beyond simple sound level readings.

Octave Band Analysis

Industrial noise varies significantly across the frequency spectrum, and effective control measures must target the dominant frequency bands. Octave band analysis divides the audible spectrum into standardised bands centred at 31.5, 63, 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. This information proves crucial for selecting appropriate acoustic materials and designing effective enclosures or silencers.

For instance, low-frequency noise below 250 Hz—common with large fans, compressors, and diesel generators—requires substantially more massive barriers and deeper absorption materials than high-frequency noise. A 100 mm thick fibreglass absorber provides excellent absorption at 1000 Hz but offers minimal benefit at 125 Hz, where a 300 mm thick treatment might be necessary.

Sound Power vs. Sound Pressure

Understanding the distinction between sound power (measured in watts) and sound pressure (measured in pascals or decibels) is essential for accurate equipment comparison and facility planning. Sound power represents the total acoustic energy emitted by a source and remains constant regardless of the acoustic environment. Sound pressure, conversely, varies with distance from the source and room acoustics.

Equipment manufacturers should provide sound power data according to ISO 3744 or similar standards, allowing engineers to predict sound pressure levels at any location within a facility. This capability proves invaluable when planning equipment layouts or assessing the impact of new machinery installations.

Noise Mapping and Modelling

Modern computational tools enable engineers to create detailed noise maps of industrial facilities, identifying high-exposure areas and evaluating proposed control measures before implementation. These models incorporate room geometry, surface absorption characteristics, equipment sound power levels, and worker locations to predict noise exposure with reasonable accuracy.

For facilities in Nova Scotia's industrial parks or those near residential areas, external noise propagation modelling helps ensure compliance with municipal noise bylaws and provincial environmental guidelines. Such modelling accounts for factors including atmospheric absorption, ground effects, and barrier diffraction to predict community noise impacts.

Engineering Solutions for Common Industrial Noise Sources

Practical noise control engineering requires matching specific solutions to particular noise sources. The following sections address common industrial noise challenges encountered in Atlantic Canadian facilities.

Fan and Blower Noise Control

Fans represent one of the most prevalent noise sources in industrial facilities, with sound generation mechanisms including blade passage frequency, turbulence, and motor noise. Effective control measures include:

• Inlet and outlet silencers – Dissipative silencers lined with acoustic absorption material can provide 15-25 dB attenuation depending on length and design

• Flexible connections – Canvas or rubber duct connections prevent vibration transmission to ductwork

• Aerodynamic improvements – Inlet cones, outlet diffusers, and optimised duct transitions reduce turbulence-generated noise

• Speed reduction – Variable speed operation matched to actual demand reduces noise while improving energy efficiency

The blade passage frequency (BPF), calculated as the product of blade count and rotational speed in Hz, often dominates fan noise spectra. For a 6-blade fan operating at 1750 RPM, the BPF equals 175 Hz—a low-frequency tone that requires careful treatment.

Compressor Noise Mitigation

Air compressors, essential to countless industrial processes throughout the Maritimes, generate substantial noise from multiple mechanisms including pulsating gas flow, mechanical impacts, and motor noise. Comprehensive compressor noise control typically involves:

• Acoustic enclosures – Purpose-built enclosures with adequate ventilation can provide 20-35 dB insertion loss

• Intake silencers – Reactive or dissipative silencers reduce airborne noise at the compressor inlet

• Pulsation dampeners – Receiver tanks and in-line dampeners reduce discharge piping noise

• Vibration isolation – Spring or elastomeric mounts prevent structure-borne noise transmission

Screw compressors generally operate 5-10 dB(A) quieter than equivalent reciprocating units, making them preferred choices for noise-sensitive installations. Oil-injected screw compressors offer additional noise benefits compared to oil-free designs.

Pump and Piping System Noise

Fluid handling systems create noise through cavitation, turbulent flow, water hammer, and mechanical sources. Many fish processing plants and food manufacturing facilities in Nova Scotia struggle with piping noise that propagates throughout buildings via pipe hangers and supports.

Effective mitigation strategies include maintaining adequate NPSH (Net Positive Suction Head) margins of at least 1.5 metres to prevent cavitation, limiting pipe velocities to 2.5-3 metres per second for liquids and 15-20 metres per second for gases, installing resilient pipe supports and penetration seals, and properly sizing pressure relief and control valves to prevent excessive pressure drops.

Acoustic Enclosure Design Principles

Acoustic enclosures represent one of the most versatile and effective noise control solutions for industrial equipment. Proper enclosure design requires careful consideration of multiple factors to achieve target noise reductions without compromising equipment operation or maintenance access.

Panel Construction

Effective acoustic panels combine mass for sound transmission loss with absorption for reverberant noise control. A typical industrial enclosure panel might comprise 16-gauge steel outer skin, 50-75 mm mineral wool or fibreglass insulation (density 48-96 kg/m³), perforated inner liner for absorption protection, and an overall surface density of 15-25 kg/m² depending on low-frequency requirements.

Composite panels with constrained layer damping provide superior performance for equipment generating significant low-frequency noise. These panels incorporate a viscoelastic damping layer between steel sheets, converting vibrational energy to heat rather than radiated sound.

Ventilation and Cooling

Most enclosed equipment requires ventilation for cooling, creating potential acoustic weak points in the enclosure. Silenced ventilation systems must balance acoustic performance with airflow requirements, typically maintaining equipment operating temperatures within 10-15°C of ambient conditions.

Properly designed ventilation silencers should provide insertion loss matching or exceeding the enclosure panel transmission loss. For a 25 dB(A) enclosure, inlet and outlet silencers each providing 25-30 dB attenuation prevent ventilation openings from compromising overall performance.

Access and Maintenance Provisions

Acoustic enclosures must accommodate routine maintenance without excessive production downtime. Design features including quick-release panel systems, observation windows with acoustic glazing, and properly sealed access doors ensure that enclosures remain practical for facility personnel. Acoustically rated doors with double seals and automatic door bottoms maintain enclosure integrity while permitting necessary access.

Vibration Control and Structure-Borne Noise

Structure-borne noise transmission often proves more challenging than airborne noise control, particularly in multi-storey industrial buildings and facilities constructed on Maritime bedrock with efficient vibration transmission characteristics.

Vibration Isolation System Design

Effective vibration isolation requires matching isolator natural frequency to equipment operating characteristics. The isolation system natural frequency should be at least one-third, preferably one-quarter, of the lowest disturbing frequency. For a motor operating at 1750 RPM (29.2 Hz), isolators providing a 7-8 Hz natural frequency would achieve approximately 95% isolation efficiency.

Steel spring isolators provide excellent low-frequency isolation but may transmit high-frequency vibration through the spring wire itself. Combination spring-elastomer mounts address this limitation, providing broadband isolation suitable for most industrial applications.

Inertia Bases

Heavy equipment such as reciprocating compressors and large pumps often requires inertia bases to reduce vibration amplitude and lower the system centre of gravity. A properly designed inertia base typically weighs 1.5-3 times the equipment weight, providing stable support while improving isolation system performance.

Concrete inertia bases with steel frames offer excellent performance for permanent installations, while fabricated steel bases filled with sand or concrete provide similar benefits with easier relocation capability—an important consideration for facilities anticipating future modifications.

Regulatory Compliance and Best Practices

Industrial facilities in Nova Scotia must comply with multiple noise-related regulations at provincial and municipal levels. Understanding these requirements helps facility managers prioritise noise control investments and avoid costly compliance issues.

The Nova Scotia Environment Act and associated guidelines establish community noise limits that vary by land use classification and time of day. Industrial facilities near residential areas typically face limits of 65 dB(A) during daytime hours (0700-1900) and 55-60 dB(A) at night. Achieving these limits while operating equipment with sound power levels exceeding 100 dB(A) requires careful facility design and appropriate noise control measures.

Beyond regulatory compliance, proactive noise control programmes demonstrate corporate responsibility and support positive community relations—particularly important for industrial operations in smaller Maritime communities where facilities and residences may exist in close proximity.

Partner with Sangster Engineering Ltd. for Your Noise Control Challenges

Effective industrial noise control requires the integration of acoustic engineering principles with practical knowledge of industrial equipment and processes. At Sangster Engineering Ltd., our mechanical engineering team brings decades of experience serving industrial clients throughout Nova Scotia and Atlantic Canada.

From initial noise assessments and acoustic modelling to detailed engineering design and implementation oversight, we provide comprehensive noise control solutions tailored to your facility's specific requirements and budget constraints. Our familiarity with regional industries—including manufacturing, food processing, and resource extraction—enables us to deliver practical, cost-effective solutions that address your noise challenges while maintaining operational efficiency.

Whether you're facing regulatory compliance deadlines, worker exposure concerns, or community noise complaints, contact Sangster Engineering Ltd. today to discuss how our professional engineering services can help you achieve a quieter, safer, and more productive facility. Our Amherst office serves clients throughout the Maritime provinces, and we welcome the opportunity to put our expertise to work for your organisation.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.