What is Noise, Vibration, and Harshness?

Why does NVH matter?

Noise and vibration are prominent elements of a passenger’s experience in a vehicle. NVH optimization allows automotive manufacturers to limit unwanted sounds and sensations (like loud roaring and jarring rumbling) while enhancing desirable ones (like the growl of a sports car or motorcycle). Electric vehicles, with different powertrains and lightweighting requirements, pose their own unique challenges.

As a result, proper NVH management in a passenger vehicle is critical to enhance comfort and safety, improve perceived quality, and differentiate a brand from its competition.

What is noise?

The sounds produced by a machine’s operation are referred to as noise, an objective, physical quantity spanning audible frequencies that can be measured in Hertz (Hz), often with issues concentrated from tens of Hz into several kHz (typically from 20 to 5,000 Hz, and sometimes beyond). Noise is primarily carried to the passenger through the air (airborne).

What is vibration?

The mechanical oscillation felt throughout a machine during operation is called vibration, and is typically most impactful from a few Hz up to the low hundreds of Hz, in most cases from 1 to 200 Hz. Vibration is primarily carried to the passenger through the structure (structure-borne).

How to optimize NVH

Airborne noise is addressed primarily with sealing, absorption and barriers; damping of vibrating panels can also reduce airborne noise indirectly by lowering sound radiation. Structure-borne vibration, transmitted for example by the steering wheel, floor or seat, is addressed with isolation (mounts/bushings) and damping within the structure.

Damping

In NVH and automotive materials, damping limits mechanical vibrations by converting their energy into heat.

Viscoelastic materials are both elastic (springy) and viscous (fluid-like). When a slow physical force is applied, their molecules move against each other like a fluid, creating friction that dissipates the physical energy as heat. This gives them a high loss factor, or ability to convert physical force to heat, that allows them to absorb vibrations instead of transmitting them to the rest of the vehicle.

Optimization process

NVH optimization begins with measurement through both objective methods (microphones, accelerometers, dynamometers, and more) and subjective methods (user-experience harshness tests). Through a combination of acoustic modeling and real-world testing, engineers select the right designs and materials to limit NVH issues.

Other NVH solutions are more common in industrial & construction, electronics, and certain transportation industries, such as floating floors in trains, damped equipment mounts in airplanes, and hatch sealing in boats.

Choosing elastomers & TPEs for NVH in mobility

Elastomers and thermoplastic elastomers (TPEs) are highly customizable and suitable for almost any NVH damping application, in both isolation systems and general damping.

• Hardness: Consider the required hardness of your application. Options range from very soft thermoplastic elastomer gels to hard, durable plastics.
• Damping ability: Prioritize key mechanical properties such as damping ability (higher loss factor) and elasticity, and determine the temperatures and frequencies your application requires.
• Density: Where weight targets are a consideration, prioritize materials that offer high damping at low density.
• Fatigue and crack growth: For long-lasting components, ensure that parts that will be repeatedly compressed or stressed use materials with resistance to fatigue and crack growth.
• Chemical and oil resistance: Identify what the material will be exposed to, especially for use in isolation systems within the powertrain.
• Processing: Consider processing, lightweighting, and recyclability when comparing remoldable thermoplastic elastomers to traditional thermoset rubbers.
• Compatibility: Confirm the compatibility of the material with substrates when injection molding, overmolding, bonding, or using polymer adhesives. Check for form-factor compatibility when deciding on use in molded parts, laminates, films, or pressure-sensitive adhesives.

Materials to reduce noise, vibration, and harshness

Elastomers—including rubber and polyurethane—primarily provide isolation by tuning stiffness to reduce force transmission, while their inherent viscoelasticity also contributes secondary damping. Polyvinyl chloride is most commonly used as an acoustic barrier or insulation material due to its density and flexibility, rather than as a primary damping medium.

In contrast, viscoelastic polymers formulated specifically for damping—such as those used in specialized damping sheets and constrained-layer damping (CLD) systems—are among the most effective materials for reducing structural vibration and radiated noise.

Kuraray’s TPEs and Elastomers

Viscoelastic polymers combine the properties of rubber and plastic in a material that is durable, highly processable, effective across broad temperature ranges, and excellent at absorbing and dissipating energy.

Conclusion

Viscoelastic polymers, such as thermoplastic elastomers, are an ideal material for NVH damping in both isolation systems and structural damping. To learn more about Kuraray’s elastomers for use in NVH damping, reach out to our experts using the contact form below.