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Quiet your inner cab

Off-highway cabs are never going to be sanctuaries of silence, but they’re getting closer. Elements as diverse as glass, electronics and push buttons are being selected in part for their benefits in reducing sound levels.

Regulators have taken aim at external noise from engines and hydraulics, bringing significant benefits for operators. As design engineers work on engines, frames and interior components, they’re focusing on making cabs quieter to reduce noises that can cause stress.

Design tools are a critical factor in these efforts. FEV North America utilizes tools like its proprietary Vehicle Interior Noise Simulation software to optimize interior noise levels and sound quality. This time-domain transfer path analysis tool helps developers reduce noise levels by managing pathways for sound.

“This allows us to identify potential areas of noise, vibration and harshness (NVH) improvement by identifying the most relevant airborne and structure-borne sources and noise paths, which contribute to interior sound quality,” said Stephan Tarnutzer, Vice President of Electronics at FEV. “Many applications currently applied to automotive technology can be integrated to mitigate in-cab noise, such as active vibration reduction (e.g., active powertrain mounts) and active noise control, including sound enhancements and noise cancellation technologies.”

The shift from hydraulic to electronic joysticks has made a significant improvement in many fields. That transition is expected to continue as excavators and other vehicles adopt digital controls.

“Hydraulics means noise; the noise of hydraulic pumps gets louder as other parameters get quieter,” said Rüediger Hüttmann, Product Manager at Danfoss. “People want to get these pumps out of the cabin.”

Even the clicks from push buttons are changing as the sound of silence becomes more important. The trend to lower volumes extends down to the push buttons in joysticks and elsewhere. Switch designers say they’re increasingly being asked to design components that provide physical feedback that doesn’t include a loud click.

“Some companies want quiet actuation, others want loud audio feedback, though things are going to quieter operations in general,” said Owen Camden, Director of Product Management and Marketing at C&K Components. “We can do things with domes, actuators and materials to provide the full gamut of sounds and physical feedback.”

When joysticks, steering and other controls transition to by-wire technologies, operators lose the feedback they’ve relied on for years. That’s forcing system designers to come up with techniques that give operators response so they know how operating parameters are changing.

“Haptics and dynamic force feedback help us simulate hydraulic joysticks,” Hüttmann said. “They bring back the feelings that go away when electronics replace hydraulics.”

Many cabs use more glass to give operators more visibility into work areas. That adds to the challenge of engineers tasked with blocking sounds.

“Typical enablers include increased glass thickness or tuning of the polyvinyl butyral damping material between layers of glass to mitigate any identified NVH deficiencies,” Tarnutzer said. “Two typical approaches are used in the development of vehicle acoustic packages: blocking noise by using dense barrier material or absorbing noise using lighter open cell materials for acoustic energy reduction.”

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