An NVH (Non-Vibration Hygiene) laboratory is more than just a soundproof chamber and a microphone system. To generate reliable data, the entire system—from the chamber structure and vibration damping to the measuring and data acquisition equipment and analysis software—must be designed to suit the testing objectives.
Especially for product development labs, correctly defining the scope of testing from the outset will directly impact infrastructure design, equipment configuration, and investment costs.
Essentially, the requirements can be divided into four groups: infrastructure, measurement equipment systems, data collection and analysis systems, and people and operating procedures.
1. Infrastructure – the foundation of measurement
The measurement environment directly affects signal quality. A highly accurate sensor system will still not produce good results if the test room is affected by external noise or vibrations.
Non-sonic chamber
For NVH measurements on vehicles or components, the semi-non-sonic chamber is one of the most important components.
The design requirements to consider include:
- Sound absorption capacity and sound field characteristics of the room according to applicable standards.
- The frequency limit of the test chamber depends on the chamber size, absorption structure, and measurement objective.
- Reflective flooring for semi-asonic chambers allows measurements to be taken under conditions suitable for the test configuration.
- The chamber size must accommodate the test object, the measurement distance, and the equipment placement.
The size or frequency limits of the chamber should not be determined based solely on a single standard parameter. The design should take into account both the test object and the measurement method.
Vibration damping system and foundation
Vibrations from traffic, machinery, or building systems can travel into the test area and affect measurements.
Some commonly considered solutions include:
- The foundation or test platform is separated from the main structure of the building.
- Vibration isolation systems utilize springs, cushions, or other suitable isolation solutions.
- The equipment platform is designed according to the load and vibration characteristics of the equipment.
- Monitor ground vibration before and after system installation.
For the NVH room, vibration control is not only aimed at protecting equipment but, more importantly, at reducing the impact of external vibrations on the measurement signals.
Environmental control
Temperature, humidity, and ventilation systems also need to be considered in the design.
HVAC systems must meet the requirements for stable temperature and humidity of equipment while minimizing noise generated by fans and airflow.
Ventilation ducts need to be designed with airflow velocity, placement, and soundproofing solutions in mind to avoid creating additional noise sources during testing.
2. Measurement equipment system – the component that directly receives the signal.
After controlling the measurement environment, the next step is to select the appropriate equipment for each test.
Accelerometer
Accelerometers are used to measure vibrations in structures. Single-axis or tri-axis sensors can be selected depending on the direction of vibration and the measurement objective.
Common locations include the engine mounts, chassis, suspension system, floor, seats, transmission assembly, and structural components.
Sound measuring microphone
Microphones are used to measure sound pressure at specific locations inside or outside the vehicle.
Depending on the testing objective, the system may utilize a free-field measuring microphone, a pressure field measuring microphone, or an acoustic intensity transducer.
The selection should be based on the frequency range, sound pressure level, sensitivity, and environmental conditions at the measurement location.
Force sensor
Force sensors are used in tests that require determining the excitation force or response of a structure. They are a crucial component in modal analysis and vibration transmission characterization.
Force hammer
The force hammer provides pulsed excitation for experimental modal analysis. The hammer head can be selected according to the material and frequency range to be excited.
Vibration machine
Vibrators produce controlled stimuli to the test object. This system is commonly used in modal analysis, vibration characterization, and simulation tests of operating conditions.
Roller system
For full vehicle testing, the roller system helps control speed and load conditions during the measurement process. Controlling operating conditions increases repeatability between tests and reduces the impact of real-world road conditions.
3. Data collection and analysis system
Signals from the microphone, accelerometer, and force sensor need to be collected simultaneously before being fed into the analysis.
Multi-channel data collection system
The data acquisition system performs functions such as signal conditioning, amplification, analog-to-digital conversion, and synchronization of measurement channels.
The number of channels is not the only factor to consider. Sampling frequency, frequency range, signal conditioning quality, and synchronization capabilities between channels also directly affect the results.
For a lab with many different measurements, the data acquisition system should be designed to be scalable rather than just meeting the requirements of a specific test.
FFT analysis
FFT analysis is used to transform signals from the time domain to the frequency domain, helping to identify oscillating components and noise at different frequencies.
This is a fundamental analytical step in many NVH tests, but it's not always sufficient to determine the cause. For complex problems, additional analytical methods may be needed.
Modal analysis
Experimental modal analysis or operational modal analysis is used to determine the natural frequencies, damping coefficients, and vibration modes of a structure.
The results help engineers identify areas at risk of resonance and assess the impact of structural design on vibration response.
Analysis by rotational degree
For engines, gearboxes, or electric motors, step-by-step analysis allows for monitoring vibrational components related to rotational speed.
This method is particularly useful when the excitation source changes with the operating speed.
Locate the sound source.
Sound source localization systems use a combination of microphone arrays, cameras, and processing algorithms to identify the area where noise is originating.
Instead of simply knowing that noise levels are increasing at a single location, engineers can pinpoint the source of the noise on the surface or within the test area, thereby shortening the process of finding the cause.
4. People and processes – factors determining data quality.
The device is well-configured, but if the measurement process is not done properly, the data can still be inaccurate.
Professional staff
Engineers and technicians need knowledge of acoustic measurement, vibration, sensing, data acquisition, and signal processing.
More importantly, operators must understand the relationship between physical phenomena and measured signals in order to identify abnormal data.
System calibration and testing
Sensors, data acquisition systems, and measuring devices must be inspected and calibrated according to the manufacturer's requirements and applicable standards.
In addition to routine calibration, pre-measurement checks should be performed to detect sensor, cable, connector, or data acquisition channel faults.
Applicable standards
Standards should be defined based on the type of measurement and the lab's objectives. These may include standards for sound power measurement, acoustic environments, vibration analysis, or specific requirements for individual industries and testing programs.
Standards should not be defined after the lab is completed. This is one of the requirements that needs to be determined during the design phase.
The size of the lab depends on the scope of the experiment.
Not every business needs to invest in a full-fledged vehicle testing facility right away. The appropriate scale depends on the type of vehicle being tested and the intended use.
Component testing lab
Suitable for testing on bushings, shock absorbers, interior components, small assemblies, or individual parts.
These systems are typically smaller in scale, focusing on measurement devices, stimulation systems, and data analysis capabilities.
Cluster system testing lab
Suitable for assemblies such as drivetrains, gearboxes, electric motors, or systems requiring operating condition monitoring.
In addition to the measuring system, a dynamometer system, a vibration exciter, and a vibration isolation system suitable for the test load may be required.
Full vehicle testing lab
This is a larger level of investment, typically requiring a large-sized semi-attenuated chamber, roller systems, vibration damping systems, and synchronized measuring equipment.
The design must simultaneously address requirements for space, load capacity, power supply, ventilation, background noise, ground vibration, and vehicle accessibility.
Defining the scope correctly from the outset helps avoid under-investment or building a system that exceeds actual needs.
5. Key investment areas
|
Category |
Main technical requirements |
Role |
|
Test chamber |
Sound-absorbing structure, sound field characteristics conforming to ISO 3745 standards, 50 Hz cut-off. |
Soundproofing, creating a standard measurement environment. |
|
Foundation |
Separate structure, pneumatic spring |
Vibration from the external environment |
|
Sensor |
Accelerometer, microphone, force sensor |
Collect vibration and sound data. |
|
Stimulation device |
Power hammers, vibratory jacks, roller systems |
Generate oscillations for analysis. |
|
Software |
FFT, modal, level analysis, sound source localization |
Processing and interpreting measurement data |
|
Environment |
Accurate HVAC, background noise below 22 dB(A) |
Maintain stable measurement conditions. |
6. Incorrect investments can lead to higher costs.
A poorly designed NVH lab can cause problems right from the start of operation.
If the system does not meet the testing requirements, the business may have to outsource or add equipment after the lab is complete. If the measurement environment is not well controlled, the data obtained may lack reliability and affect engineering decisions.
Conversely, making a large investment right from the start is not the optimal choice if the business does not yet have a corresponding need for it.
Therefore, the crucial challenge is not building the largest lab, but rather building a system that meets the specific testing objectives and is scalable as needs increase.
7. GPower Vietnam – Consulting on laboratory solutions for cultural centers.
Building an NVH laboratory should be approached from the experimental problem-solving perspective, rather than starting with a list of equipment.
GPower Vietnam can provide support from the initial needs assessment, selection of measurement configurations, sensors, and data acquisition systems to analysis, integration, and maintenance solutions.
The goal is to build a system capable of meeting real-world measurement requirements, ensuring synchronization between components, and scalability to meet the evolving needs of the lab.
Contact GPower Vietnam to discuss your NVH laboratory construction or upgrade requirements.
Info@gpower.com.vn
