Urbanization is accelerating, and with it comes the heightened demand for construction and heavy machinery operations. This has greatly increased the number of people adversely affected by noise pollution.
Regulatory bodies have sharpened their focus on noise emissions, with resulting regulations trickling down to OEMs and component suppliers — tasked with ensuring their machinery meets new standards. And while electrified machinery offers notable noise reductions compared to internal combustion engines (ICE), further refinements are necessary.
Comprehensive noise management means understanding the electrical components prone to producing noise and strategies to ensure they meet the needs of both the application and a tightening regulatory environment.
Electric Drivetrain Components: Challenges to Quiet Operations
Electric powertrains are the heart of an electric vehicle’s (EV) relatively quiet operation. Interestingly, achieving absolute silence is not the objective.
For pedestrian safety, regulatory bodies have established minimum sound requirements for electric vehicles, often ranging between 47 and 67 decibels (dB). Achieving this regulated sound range depends heavily on the design and integration of the following electric drivetrain components.
Gearbox Noise Reduction
Electric motors in EVs often operate at high speeds, requiring gearboxes to reduce speed and create torque. Without precise design tailored to specific applications, gearboxes can become prominent sources of noise due to their inherent vibration behaviors.
To address this issue, OEMs often focus on:
- Utilizing precision-engineered gear designs, such as angled helical gears, to minimize noise.
- Ensuring regular maintenance and proper lubrication of gearboxes to prevent noise escalation.
- Optimizing gear ratios to balance performance and noise output.
Vibration-dampening mounts and noise-insulating materials are also critical noise-reduction methods. These technologies isolate the gearbox mechanically, preventing vibrations from propagating sound throughout the vehicle’s structure.
Innovative research into resonant “metamaterials” for gearbox housings further hints at the possibility of achieving increasingly lightweight and noise-free operations, although current design complexities limit practical application.
READ MORE: Understanding the Types of Electric Motors Available for Electric Vehicles
Managing Pump and Fan Noise
Critical components like pumps and fans must also be meticulously designed, walking a delicate line between noise and heat management. Best practices include:
- Selecting high-quality pumps that operate more quietly.
- Implementing variable fan speeds to adjust noise levels dynamically based on cooling needs.
- Utilizing noise-optimized fan blades to reduce acoustic output without compromising performance.
Component quality directly influences the overall noise level of the powertrain; lower-quality offerings tend to contribute to increased noise emissions.
Addressing Unwanted Sound from Power Electronics
Somewhat ironically, lack of a combustion engine often accentuates noise from certain components — at least from an operator’s perspective. Whereas ICE masks various rattles and vibrations, quieter electric powertrains have prompted full cab redesigns to ensure better-quality driving experiences.
One common culprit is an EV’s power electronics, particularly during the switch-mode transformation phase, which can result in high-frequency noises. While not a significant contributor to external noise pollution, this noise can be bothersome to operators, reminiscent of the high-pitched whine from older plasma or LCD televisions.
To address this particular issue, OEMs should note the following:
- Most commonly, the switched-mode power supply is the cause of this noise, produced by the switching frequency dropping below 20 kHz.
- This noise does not necessarily indicate machine failure — simply an adaptation to the load and input voltage.
- Utilizing Gallium Nitride (GaN) and Silicon Carbide (SiC) wide bandgap semiconductors may solve this, as they offer higher power and faster switching that often renders the frequency inaudible.
Once again, the solution largely hinges on quality; component selection is crucial, as is circuit design.
READ MORE: Choosing the Right Material for Soundproofing and Vibration Control in Hydraulic Systems
Charger Noise Management Strategies
Noise reduction in charger systems is a critical yet often overlooked aspect of noise pollution control in electric vehicle infrastructure.
Unlike electrified machinery, which operates only during work hours, chargers may run for extended periods, often up to 16 hours a day. This makes charger noise management crucial, perhaps even more so than the drivetrain itself.
Address Fan Noise During Charging
Charger cooling fans present unique challenges, particularly since users do not typically expect noise when a machine is parked and charging.
In contrast to powertrains, where operational sounds mask fan noise, the quiet environment during charging makes fan noise more disruptive. This is exacerbated by the fact that charging sessions can last anywhere from 8-16 hours, creating a prolonged period where fan noise can become a significant source of complaints.
To address this, OEMs are increasingly exploring solutions such as adaptive fan speeds that adjust to real-time thermal management needs, or isolating and soundproofing charger units to reduce noise during extended charging periods.
Mitigate Indirect Noise from Electromagnetic Interference
Older or dysfunctional chargers can induce noise in nearby devices, or even in building power lines. This interference can manifest as unusual sounds, flickering lights, or other disturbances while the chargers operate.
Strategies to mitigate these effects include:
- Only utilizing high-quality charging solutions properly matched to your machinery’s specific application.
- Installing electromagnetic interference (EMI) filters in power lines to protect against unwanted transmission.
- Learning about (and testing compatibility with) relevant electromagnetic compatibility (EMC) standards
This type of interference is especially problematic when multiple chargers operate simultaneously, such as in fleet scenarios with electric golf carts or industrial machinery, making these strategies even more essential.
The Role of Battery Design and Maintenance in Noise Reduction
Batteries themselves are not typically direct sources of audible noise in vehicles, yet they can significantly influence noise levels through their installation, charging, and maintenance practices. In particular, poorly maintained batteries can lead to increased heat generation, requiring louder cooling solutions.
Best practices for battery management include:
- Battery management system (BMS) software – Utilizing a sophisticated BMS solution can optimize charging performance, which in turn minimizes noise-producing behaviors by maintaining the battery at optimal efficiency.
- Thermal management – Implementing an intelligent charging system that includes adaptive thermal management can potentially reduce noise levels, ensuring that cooling fans are only activated as needed rather than running continuously at full capacity.
- Routine maintenance – Regular upkeep is essential for battery and charging system health. Maintenance routines should include checking and cleaning electrical connections to prevent resistance build-up, which can increase heat and, subsequently, noise.
OEMs might consider adopting more advanced measures such as using multiple, modular chargers. This approach can distribute the cooling demand across several units, reducing the operational noise of each individual charger by minimizing the need for high-capacity, noisy cooling systems.
READ MORE: Navigating the Complexities of Battery and Charger Integration for Electric Vehicles
Final Design Considerations
As electrified machinery continues to evolve, noise reduction is gaining increased attention from OEMs and suppliers alike. From powertrain refinements to charger improvements and battery optimizations, a holistic approach is necessary to address the various noise sources in EVs.
Whether it's preserving the serenity of a golf course or meeting stringent noise regulations at urban worksites, only a comprehensive portfolio of electric solutions can cut through the noise and engineer a safe, sustainable future for e-mobility.
This article was written and contributed by Conway Hui, Director, Sales Application Engineering & Customer Support at Delta-Q Technologies & Martin Wennerblom, Marketing Director, Inmotion Technologies, both of which are part of the ZAPI GROUP.
