How KFB approaches NVH

The automotive industry is constantly evolving, and with it comes new challenges in vehicle NVH. Quiet transportation has become a necessity for a quieter life.
Our latest insight summarises the current trends and challenges in NVH.The approach we offer, focuses on all of the most important vehicle areas, and recommends a variety of solutions. We do not let noise and vibrations get out of hand. We make it go away.

Automotive is one of the most rapidly changing industries in the world. Cars are becoming a forefront of eco-friendly solutions instead of being a major factor in greenhouse gas production. With the increasing demand for a quieter and more comfortable driving experience, these companies are employing innovative technologies and methodologies to address NVH issues across different vehicle components.This article delves into how we approach NVH to enhance the overall driving experience.

Trends & Challenges

The automotive industry is constantly evolving to meet consumer demand for quieter and more comfortable vehicles. One critical aspect of this is NVH (Noise, Vibration, and Harshness) testing, which aims to reduce the noise and vibration levels experienced by passengers inside the vehicle.

In recent years, several trends have emerged in the global NVH market:

• Demand for quieter and comfortable vehicles
• Adoption of electric and hybrid vehicles, which require different NVH solutions due to their unique drivetrain characteristics
• Lightweight materials
• Advanced NVH testing and simulation techniques
• Adoption of active noise cancellation and other advanced NVH technologies

Electric and hybrid vehicles require unique NVH solutions due to their different drivetrain characteristics. This includes reduced engine noise and increased electric motor noise. Additionally, lightweight materials such as aluminum and composites are being used to reduce vehicle weight, but they can also contribute to increased noise and vibration levels. Therefore, manufacturers must carefully balance NVH performance with weight reduction.

How do we approach NVH

We understand the importance of addressing the NVH environment in the automotive industry. With our advanced testing and simulation techniques, we can tackle the most crucial NVH execution challenges, helping manufacturers optimize vehicle performance more efficiently. Our expertise in NVH testing and simulation enables us to offer innovative solutions that can improve the quality of the vehicles and enhance the driving experience of the users. With a focus on precision and accuracy, we are committed to delivering reliable results to our clients. A well-designed NVH testing and simulation strategy can help manufacturers stay ahead of the competition and meet the evolving demands of the market.

The most important NVH challenges would include:

• Limited access to prototypes, making it critical to streamline the testing process,
• Quick and easy microphone positioning – a crucial factor in recording repeatable results,
• Microphone placement should minimise the impact of structure-borne sound,
• The installation process should also be safe for the test engineer to carry out during vehicle testing,
• Calibration verification should be simple and easy to perform to ensure accurate and reliable test results.

Now, when it comes to testing methods in NVH, the most efficient ones would include impact hammer testing, noise source mapping, sound intensity measurement, mechanical and product vibration testing, acoustic camera, sound quality testing, psychoacoustics, laser vibrometer, and predictive simulation. These methods are used to evaluate different aspects of NVH performance, such as: , road noise, sound package, component noise, brake noise, and computer model validations.

We also determine what are our key testing areas that we need to focus on.

1. Total interior noise, involving evaluation of the overall noise level inside the vehicle at its full speed range, which is a way of testing the general experience of a vehicle’s acoustic comfort.

The evaluation of total interior noise is a critical component of testing a vehicle’s acoustic comfort. This involves assessing the overall noise level inside the vehicle at various speeds to determine the general experience of passengers. By conducting comprehensive tests on interior noise, manufacturers can improve the overall acoustic comfort of the vehicle and enhance the driving experience for users.

2. Road noise – assessment of the contribution of road excitation to interior noise, which includes both structure-borne and airborne noise.

Road noise is a significant factor in determining the overall interior noise of a vehicle. This noise can be classified into two categories: structure-borne noise and airborne noise. Structure-borne noise is the noise that is transmitted through the vehicle’s structure, while airborne noise is the noise that enters the vehicle’s cabin through the air.

Assessing the contribution of road excitation to interior noise requires a thorough understanding of both types of noise. To accurately measure structure-borne noise, sensors can be placed at various points on the vehicle’s structure to detect vibrations caused by road excitation. The data collected from these sensors can be used to determine the frequency and magnitude of the vibrations and the resulting noise.

Similarly, airborne noise can be measured using microphones placed inside the cabin of the vehicle. The data collected from these microphones can be used to determine the frequency and magnitude of the noise inside the cabin. By comparing the data collected from both types of sensors, it is possible to determine the contribution of road excitation to the overall interior noise.

It is important to assess the contribution of road excitation to interior noise to improve the comfort and safety of the vehicle’s occupants. By identifying the sources of noise and reducing their impact, vehicle manufacturers can improve the overall driving experience for their customers. Additionally, reducing interior noise can help prevent driver fatigue, which can improve safety on the road.

3. Sound package – critical for reducing NVH levels. At this stage it’s vital to ensure that the body is sealed as much as possible. This reduces high frequency leakage and increases the overall NVH performance. Structural damping and heavy-layer isolation mats must be optimized for best performance and lowest weight and cost. Acoustic absorption material at critical locations is used to improve the acoustic interior comfort.

Sound package testing at vehicle level is done indirectly by the vehicle tests.

4. Brake Noise – Major NVH challenge for manufacturers. The noise is caused by friction-induced vibrations, which make the brake system radiate noise. Brake noise is a very complex problem and the research in this area is in continuous progress.

Brake noise is evaluated with microphones at ear level and in the wheelhouse while driving on a dedicated test route with all possible braking and different environmental conditions. Acoustic transfer function (ATF) System testing requires the usage of a lot of different acoustic sensors. These tests are performed in a NVH laboratory, either with a complete vehicle or for a system or component only. System/component level test are carried  with ATF (Acoustic Transfer Function) from engine bay to interior to verify sound package.

Noise transfer function (NTF) test are performed to measure the structural noise paths. Tests are done with the vehicle in a hemi-anechoic test bench.

Component Noise: Evaluating additional electrical or engine-driven systems customer-actuated sounds: These are directly related to an action like opening or closing a door or power operating windows and will likewise provide user feedback system-actuated sounds: These are controlled independently of any action from the driver or passengers .The HVAC system is one of the dominating noise sources in the vehicle during cool down or heat up and needs a lot of careful design work.
Component noise is tested during typical usage conditions, but isolated with no other sounds. The tests are performed in a vehicle in a hemi-anechoic test cell.

All tests are concluded in Computer Model Validations: Testing and corelating on prototype parts or vehicles with predictive simulations.
Computer model validations involve testing and correlating computer simulations with physical prototype parts or vehicles to ensure that the final product meets the desired NVH standards. This process allows for early identification and correction of NVH issues, which can save time and money, and ultimately result in a more comfortable and pleasant driving experience.

Summary

In conclusion, the global NVH market is continuously evolving to meet the demand for quieter and more comfortable vehicles. The adoption of electric and hybrid vehicles, lightweight materials, and advanced testing and simulation techniques is driving the development of advanced NVH solutions. Manufacturers face several challenges in NVH testing, including limited access to prototypes, quick and easy microphone positioning, and safe installation processes. However, testing methods and our expertise can bring a brand new quality in optimization of NVH performance more efficiently. Ultimately, these efforts are aimed at providing a more enjoyable driving experience for passengers.