Pehea e hoʻomaikaʻi ai nā mea leo kaʻa i ka ʻoluʻolu o ke keʻena | Alakaʻi NVH

How Automotive Acoustic Materials Improve Cabin Comfort

For automotive OEM and Tier 1 engineers, cabin comfort is not simply about reducing a few decibels.

Effective automotive acoustic engineering starts with three fundamental questions:

• No hea mai ka leo?
• How does it travel into the cabin?
• Which material or structural solution is best suited to control it?

In automotive NVH engineering, noise generally reaches the passenger compartment through two primary paths:

• Ka halulu lewa
• Structure-borne noise

Understanding the difference between these two transmission paths is essential when selecting automotive acoustic absorbers, insulation materials, damping layers, decouplers, and multilayer acoustic systems.

Pane wikiwiki

Automotive acoustic materials improve cabin comfort by controlling sound and vibration through several different mechanisms.

Porous fiber materials are mainly used to absorb airborne sound.

Damping materials help reduce panel vibration.

Barrier layers reduce sound transmission.

Decoupling materials help limit vibration transfer between structures.

In real vehicle applications, these functions are often combined into an integrated acoustic package rather than relying on a single material to solve every NVH problem.

1. What Is Automotive NVH?

NVH stands for:

• Noise
• kamakawiwo ole
• ʻoʻoleʻa

Together, these factors strongly influence how drivers and passengers perceive vehicle comfort and quality.

Noise

Noise refers to the sound heard by vehicle occupants.

Typical automotive noise sources include:

• Tire and road noise
• Ka walaʻau makani
• Ka walaʻau o ka ʻenekini
• Electric motor noise
• Gear whine
• HVAC noise
• Cooling system noise
• Body-panel radiation

Different frequency ranges create very different subjective impressions.

Low-frequency noise may be perceived as:

• ke kākoʻo
• haʻalulu
• droning

Higher-frequency noise may be perceived as:

• ʻūhū
• hoʻowahāwahā
• sharp tonal noise
• electric motor high-frequency noise

This is why overall sound pressure level alone cannot fully describe cabin acoustic quality.

kamakawiwo ole

Vibration originates from mechanical excitation.

ʻO nā kumu maʻamau:

• Tire-road interaction
• Suspension movement
• Powertrain excitation
• ʻO nā ʻaka uila
• Nā ʻōnaehana kia
• ʻO ke kani ʻana o ka hale

These vibrations can travel through:

• Nā mea hoʻomaha
• Nā ʻāpana liʻiliʻi
• kaʻa
• Pane kino
• Seat rails
• Nā ʻōnaehana hoʻokele

Some vibrations are directly perceived by occupants.

Others excite body panels, which then radiate sound into the cabin.

ʻoʻoleʻa

Harshness refers more to the subjective perception of vehicle vibration and sound quality than to a single physical parameter.

Eia nāʻano:

• Strong impact when driving over road irregularities
• Excessive low-frequency vibration
• Cabin booming at specific vehicle speeds
• Unpleasant structural resonance

The objective of good NVH engineering is therefore not to eliminate every sound.

It is to control undesirable acoustic and vibration energy.

2. How Does Noise Enter the Vehicle Cabin?

From a transmission-path perspective, automotive cabin noise can generally be divided into two major categories:

Airborne Noise

a

Walaʻau i lawe ʻia e ke ʻano

These two mechanisms require different control strategies.

3. What Is Airborne Noise?

Airborne noise is sound energy that primarily travels through the air before reaching the passenger compartment.

For example, tire-road interaction generates acoustic energy around the wheel area.

Part of that sound travels through air and can enter the vehicle through the floor, wheel arch, doors, or other body structures.

Similarly, HVAC blowers generate sound that travels directly through air ducts and the cabin.

Typical airborne noise sources include:

• Ka walaʻau makani
• Tire radiation noise
• HVAC noise
• Cooling fan noise
• Exterior traffic noise
• Some electric motor noise
• Some powertrain noise

Once airborne sound enters the cabin, it can also reflect repeatedly from interior surfaces.

If the vehicle interior has insufficient sound absorption, sound energy may continue reflecting from areas such as:

• Nā Roof
• Loulou
• pani
• Dashboard
• Papa
• Kūlā

This increases the acoustic energy perceived by occupants.

That is why sound-absorbing materials are widely used throughout the vehicle interior.

4. How Do Fibrous Automotive Acoustic Materials Absorb Sound?

PP/PET fibrous acoustic materials are typical porous sound absorbers.

When a sound wave enters the fiber network, air particles move through a complex porous structure.

During this process, acoustic energy is reduced through mechanisms such as:

• Friction between air and fibers
• Viscous losses
• Thermal exchange
• Energy dissipation caused by airflow through the porous network

A small portion of the acoustic energy is ultimately converted into heat.

As a result, less sound energy is reflected back into the cabin.

This is the basic principle behind fibrous automotive acoustic absorbers.

5. Why Is Thickness Alone Not Enough?

A common assumption is that thicker acoustic material always performs better.

In reality, automotive sound absorption depends on many parameters, including:

• mānoanoa
• Kaumaha kumu
• nuʻa
• Anawaena fiber
• Fiber structure
• ʻO Porosity
• Ke kū'ē ʻana i ke kahe ʻana o ka ea
• Lākiō hoʻopilikia
• Kūlana hoʻonohonoho
• Target frequency range

One of the most important parameters is airflow resistance.

If a material is too open, sound can pass through easily, but interaction between the moving air and the fiber network may be insufficient.

If a material is too dense, too much sound may be reflected at the surface instead of entering the porous structure.

High-performance acoustic materials therefore require an appropriate balance between:

Porosity, fiber structure, and airflow resistance.

6. What Is Structure-Borne Noise?

Structure-borne noise begins as mechanical vibration transmitted through the vehicle structure.

ʻO kahi laʻana maʻamau:

Road excitation

↓

Haʻalulu o ka huila

↓

Hoʻomaha

↓

Pākuʻi lalo

↓

Vehicle body

↓

Body-panel vibration

↓

Sound radiation into the cabin

The final sound may still be heard through the air, but the original transmission path was structural.

This is the key difference between structure-borne and airborne noise.

7. Why Can Acoustic Fiber Not Solve All Structure-Borne Noise?

This is one of the most important distinctions in automotive acoustic engineering.

Porous acoustic fiber is mainly designed to absorb airborne sound energy.

If the main problem is strong vibration of a door panel, floor panel, wheelhouse, or another structural component, adding more acoustic fiber alone will not eliminate the root cause.

Structure-borne noise typically requires a combination of several control methods.

Nā Mea Hoʻohuʻu

Damping layers are used to reduce vibration amplitude in metal or composite panels.

Aia nā wahi noi maʻamau:

• Door outer panels
• Nā papa papahele
• Wheelhouse areas
• Trunk panels
• Body sheet metal

Decoupling Materials

Decoupling layers help reduce mechanical coupling between structures.

They are also important in multilayer acoustic systems where a compliant layer is required between a barrier and the vehicle body.

Mea Paʻa

Barrier layers are used to reduce sound transmission.

They typically rely on higher surface mass or multilayer construction to improve transmission loss.

Na mea hoohuoi

Absorbing layers reduce airborne sound energy once that energy reaches the cabin or acoustic package.

In practical vehicle design, these functions are often combined as:

Damping + Decoupling + Barrier + Absorption

8. Airborne and Structure-Borne Noise Are Often Coupled

In real vehicle NVH problems, airborne and structure-borne mechanisms are not completely independent.

ʻo kahi laʻana:

Road excitation first generates mechanical vibration.

That vibration travels through the suspension and body structure.

The body panel is then excited.

The vibrating panel radiates sound into the cabin air.

The full path may therefore be:

Road Excitation

↓

Structure-Borne Vibration

↓

Body-Panel Vibration

↓

Airborne Sound Radiation

↓

Passenger Perception

For this reason, OEM NVH engineers do not simply ask whether a problem is airborne or structure-borne.

They need to understand:

• Which source is dominant?
• Which transfer path contributes most?
• Which frequency range requires improvement?

9. Different Frequency Ranges Require Different NVH Strategies

No single material can effectively solve every noise problem across the entire frequency spectrum.

Different frequency ranges typically require different engineering strategies.

Frequency Frequency

Low-frequency problems are often related to:

• Body modes
• Kūleʻa hale
• Panel resonance
• Suspension excitation
• Powertrain excitation

Severe low-frequency issues usually cannot be solved by lightweight porous absorbers alone.

Typical solutions may include:

• ʻO ka hoʻolālā hoʻolālā
• Hoʻoulu
• Kaʻawale haʻalulu
• Mount optimization
• Body stiffness optimization

Mid Frequency

Mid-frequency noise often requires a combination of:

• Hoʻoulu
• Hoʻopiʻi
• Hana pale
• Omo leo

Mid-to-High Frequency

Fibrous porous absorbers are particularly useful in the mid-to-high-frequency range.

Their acoustic performance can be tuned by adjusting:

• mānoanoa
• Kaumaha kumu
• Fiber structure
• Ke kū'ē ʻana i ke kahe ʻana o ka ea

This is why automotive acoustic materials should not be evaluated by a single absorption value.

The full absorption curve across the relevant frequency range is far more meaningful.

10. Why Do Electric Vehicles Change Acoustic Material Requirements?

Electric vehicles do not make NVH engineering easier.

They change the noise spectrum.

In internal-combustion vehicles, engine noise creates a relatively strong background sound that can mask other noise sources.

In electric vehicles, this masking effect is reduced.

As a result, previously less noticeable sounds can become more prominent, including:

• Ka walaʻau o nā huila
• Walaʻau alanui
• Ka walaʻau makani
• ʻUē ka motika uila
• walaʻau kaʻa
• Inverter tonal noise
• HVAC noise
• Cooling-system noise

EV acoustic design therefore places greater emphasis on:

• Ka hoʻopili ʻana o ke kani ākea
• Mid-to-high-frequency noise control
• Māmā māmā
• Hoʻohui waiwai
• Local acoustic optimization

11. Why Are Lightweight Acoustic Materials Becoming More Important?

Adding more NVH material can improve acoustic performance.

However, additional material also increases vehicle mass.

This can directly affect:

• Kaumaha kaʻa
• Ka hoʻohanaʻana i ka ike
• EV driving range
• Uku hana
• Paʻakikī hui

For this reason, the goal is not simply to add more material.

The objective is to achieve the required acoustic performance with lower weight and less installation space.

This is one of the main advantages of fibrous automotive acoustic materials.

Ma ka hoʻoponopono ʻana:

• Huina fiber
• Kaumaha kumu
• mānoanoa
• nuʻa
• Hoʻolālā papa

the material can be optimized for different locations and vehicle platforms.

12. Where Are Automotive Acoustic Materials Used?

Different vehicle zones have different acoustic requirements.

Roof and Headliner

ʻO nā hopohopo maʻamau:

• Ka walaʻau makani
• Cabin reverberation
• Rain impact noise
• Ka hoʻopili ʻana o ke kani ākea

Low weight is particularly important in this area.

pani

Door systems may be affected by:

• Exterior airborne noise
• Door-panel vibration
• Cavity resonance
• Speaker interaction

For this reason, door acoustic systems often require both absorption and structural vibration control.

Firewall and Dashboard Area

This is one of the most important NVH control zones.

Typical noise sources include:

• Powertrain noise
• Walaʻau alanui
• HVAC noise
• Structural radiation

Multilayer acoustic systems are commonly used here rather than a single absorber.

Papa

ʻO nā hopohopo maʻamau:

• Tire-road excitation
• Suspension noise
• Underbody noise
• Kūleʻa hale

Common floor acoustic systems may include:

Absorber + Decoupler + Barrier

with localized damping where necessary.

Wheel Arch

The wheel area is one of the most important noise sources in the vehicle.

Acoustic materials used here may need to address:

• Ka walaʻau o nā huila
• Road excitation
• Stone impact
• Hōʻike wai
• Mea lawaiʻa

Therefore, material selection must also consider:

• Hoʻoikaika kūʻai
• Durability
• Ke kūʻē i ka hoʻohaumia

Kūlā

Rear-wheel and rear-body excitation can introduce significant acoustic energy into the trunk cavity.

Absorptive materials can reduce cavity reflection and help limit further sound propagation toward the passenger compartment.

Pillars and Body Cavities

Vehicle cavities can act as acoustic transmission paths.

Proper use of:

• Acoustic absorbers
• Cavity fillers
• Pūnaehana hoʻopaʻa

can reduce sound transmission through these areas.

13. Which Material Parameters Should OEM Engineers Evaluate?

Automotive acoustic materials should not be evaluated only by whether they are “good at absorbing sound.”

A more complete evaluation should include the following parameters.

Hana ʻAno

• Ka helu hoʻopalekana kani
• Frequency-dependent absorption curve
• Ke kū'ē ʻana i ke kahe ʻana o ka ea
• Ke kū'ē ʻana o ke kahe ʻana o ka ea

Nā Kino

• mānoanoa
• Kaumaha kumu
• nuʻa
• Hoʻihoʻi hoʻoemi
• Ka pale nui

Hana Kaiapuni

• Kūʻē wela
• Hoʻoikaika kūʻai
• ʻO ke kū'ēʻana

Automotive Requirements

• Kūlana
• VOC performance
• Hoʻōkuhi
• ʻO Fogging
• Hoʻohālikelike mea

Hana Hana

• ʻOki make
• ʻĀlohole
• Lami
• Kākoʻo paʻa ponoʻī
• Aluminum foil lamination
• Complex-shape conversion

kuleana

• Māmā māmā
• Hoʻohana hou
• Material simplification
• Recycled maʻiʻo

14. Why Is Installation Condition as Important as Material Data?

The same acoustic material can perform very differently under different installation conditions.

ʻO nā mea koʻikoʻi he:

• ʻĀpana lewa
• Paumaha
• Backing surface
• ʻĀpana hoʻonoho
• anahonua
• Edge leakage
• Adjacent materials
• Kūkulu ʻana o nā papa he nui

For example, a material with a free-state thickness of 20 mm may behave very differently if compressed to 8 mm after installation.

Compression can change:

• ʻO Porosity
• Ke kū'ē ʻana i ke kahe ʻana o ka ea
• Effective thickness
• Hana Acoustic

This is why automotive acoustic materials should not be evaluated only from laboratory datasheets.

Final installed condition must also be considered.

15. Transulate™ Automotive Acoustic Materials

Unuhi™ is a PP/PET bicomponent fiber material series developed by SINOYQX for automotive acoustic and thermal-management applications.

The material is designed for applications including:

• Automotive sound absorption
• Hāʻawi ka thermal
• Lightweight acoustic packages

Aia nā wahi noi maʻamau:

• Nā Roof
• Loulou
• puka
• Dashboard
• Pākuena
• Papa
• Kūlā
• kia
• Paʻi loko

Depending on the project, key material parameters can be customized, including:

• Kaumaha kumu
• mānoanoa
• nuʻa
• Fiber structure
• Lamination structure

16. How to Select the Transulate™ Series

Unuhi™ LT Series

Typical basis weight:

100–200 g/m²

mānoanoa maʻamau:

10-20 mm

Suitable for lightweight applications such as:

• Nā Roof
• Loulou
• puka
• kia
• Paʻi loko

The key focus is low weight.

Unuhi™ AP Series

Typical basis weight:

300–500 g/m²

mānoanoa maʻamau:

20-30 mm

Pono no ka:

• Pākuena
• puka
• Papa
• Kūlā
• General acoustic packages

Transulate™ HP Series

Typical basis weight:

600–900 g/m²

mānoanoa maʻamau:

30-50 mm

Suitable for applications requiring higher sound absorption and where more installation space is available.

17. What Additional Processing Options Are Available?

Depending on OEM and Tier 1 project requirements, Transulate™ can be supplied or converted as:

• Nā papa inoa
• a lahilahi
• ʻāpana ʻoki make
• Self-adhesive parts
• Aluminum-foil laminated products
• Nonwoven-faced products
• Multilayer composites
• Mānoanoa i hoʻopilikino ʻia
• Customized basis weight

The final acoustic structure should be selected according to:

Target Frequency + Installation Location + Available Space + Weight Target

18. Automotive Acoustic Engineering Is Moving from Material Selection to System Design

The future of automotive NVH development is not simply about identifying which absorber has the highest sound absorption coefficient.

ʻO nā nīnau koʻikoʻi loa:

• Which noise source is dominant?
• Which transfer path is most important?
• Which frequency range needs improvement?
• Which material is best suited to the location?
• How can the target performance be achieved with less weight?

A more effective development process is:

Identify the Noise Source

↓

Analyze the Transfer Path

↓

Define the Target Frequency

↓

Select the Control Strategy

↓

Hoʻohālikelike i ka Material

↓

Validate at Component Level

↓

Validate at Vehicle Level

This is how material performance can be converted into real cabin comfort.

Panina

Vehicle cabin comfort is not controlled by a single material.

Airborne noise is mainly managed through:

Sound absorption and sound insulation.

Structure-borne noise generally requires:

Damping, vibration isolation, decoupling, and structural optimization.

Fibrous automotive acoustic materials play an important role in reducing airborne sound energy, limiting cabin reflections, and improving mid-to-high-frequency acoustic performance.

This becomes even more important in electric vehicles, where reduced engine masking makes tire noise, wind noise, and electric-drive tonal noise more noticeable.

At the same time, vehicle manufacturers continue to reduce weight.

For this reason, the next generation of automotive acoustic systems is not about adding more material.

E pili ana ia:

Using the right material, in the right location, for the right frequency range.

Transulate™ automotive acoustic materials can be customized according to OEM and Tier 1 requirements, including application location, target frequency, thickness, basis weight, lamination structure, and annual demand.

Pinepine ninau ninaninau 'ana i

What is the difference between airborne noise and structure-borne noise in a vehicle?

Airborne noise travels primarily through air, such as wind noise, HVAC noise, and some tire noise.

Structure-borne noise begins as mechanical vibration transmitted through the suspension, body, or other structural components before being radiated as sound.

Can automotive acoustic fiber directly reduce structure-borne noise?

ʻAʻole loa.

Porous fibrous materials primarily absorb airborne sound.

If the main problem is structural panel vibration, additional damping, isolation, decoupling, or structural optimization is usually required.

What are the most important parameters for automotive sound absorbers?

Important parameters include thickness, basis weight, fiber structure, airflow resistance, absorption performance across frequency, compression condition, installation gap, and target frequency range.

Why are lightweight acoustic materials important for electric vehicles?

Electric vehicles have less engine masking noise, so tire noise, wind noise, electric motor noise, and other high-frequency sounds become more noticeable.

At the same time, lower vehicle mass helps improve energy efficiency and driving range.

Where can Transulate™ automotive acoustic materials be used?

Typical applications include roof, headliner, doors, firewall, dashboard, floor, trunk, pillars, and interior trim.

The final material specification should be selected according to installation space, target frequency, basis weight, and thickness requirements.