Modern noise and vibration measuring equipment in the NVH laboratory

A modern NVH lab is more than just a quiet room with a few microphones. It's a complex ecosystem of equipment where each instrument plays a distinct role in the measurement chain—from capturing physical signals, converting them to digital data, analyzing frequency spectra, to outputting usable results for engineering decision-making. Understanding each piece of equipment is a prerequisite for building and operating a truly effective NVH lab.

Sound Measurement Microphone

Measurement microphones are the most basic input device in any NVH lab. Unlike regular microphones optimized for musical quality, measurement microphones are designed to reproduce the audio signal as faithfully as possible—no adding, no subtracting, no coloring.

The most common type of microphone in automotive NVH applications is the condenser microphone, which features a thin metal diaphragm. They have a frequency range from 20 Hz to 20,000 Hz, covering the entire range of human hearing, with high sensitivity and extremely low internal noise. In practical testing, the microphones were placed in various locations:

• - Interior noise is measured at the driver's and passenger's ear positions.
• - The exterior of the vehicle is configured according to ECE R51 standards to measure exterior noise (pass-by noise).
• - Place the sound source near specific sources such as the gearbox, fan, or braking system to isolate and pinpoint the source.

An important parameter when choosing a microphone is dynamic range – the ability to accurately measure both very low and very high sounds in a single measurement. In a soundproof room, background noise levels can drop below 15 dB – lower than the normal human hearing threshold – and the microphone must be sensitive enough to work in that environment.

Accelerometer (Accelerometer Sensor)

If the microphone is the "ear" of the NVH lab, then the accelerometer is the "hand"—a tool for sensing vibrations transmitted through the material's structure rather than through the air.

Accelerometers measure the acceleration of a point on a structure along one or more axes. The most common type in NVH (Non-Variable Hygiene) systems is the piezoelectric accelerometer, which operates on the principle that piezoelectric materials generate voltage when subjected to mechanical stress. They have a wide frequency range (from below 1 Hz to tens of kHz), are compact in size, and can be mounted on most structural surfaces without altering the vibration characteristics of the measured component.

In a typical NVH test, dozens to hundreds of accelerometers may be mounted simultaneously on the vehicle—at the engine mounts, chassis, floor, steering column, seats, and every intermediate point along the vibration transmission path. Data from all sensors is collected synchronously, allowing engineers to map the complete vibration propagation through the entire vehicle structure.

In addition to traditional single-axis accelerometers, modern laboratories also use triaxial accelerometers to simultaneously measure vibrations in all three spatial dimensions at a single point – saving installation time and providing a more comprehensive view of structural movement.

Data Acquisition System (DAQ)

Microphones and accelerometers are merely inputs. To transform data from dozens of sensors simultaneously into analyzeable information, a data acquisition system (DAQ) is necessary.

A DAQ system in the NVH lab includes:

• - Signal conditioner/amplifier: Boosts weak signals from the sensor to a sufficient level for processing, while filtering out electronic noise.
• - Analog-to-Digital Converter (ADC): Converts analog electrical signals from the sensor into digital data. The sampling rate must be at least double the highest frequency to be measured – to measure up to 20,000 Hz, the minimum sampling rate must be 40,000 samples/second.
• - Synchronization unit: Ensures that all measurement channels are sampled at the same time, allowing for accurate correlation analysis between signals.

Leading DAQ systems in the automotive NVH industry today, from brands like Brüel & Kjær, LMS (Siemens), or HEAD acoustics , can simultaneously process from 16 to over 1,000 channels with sampling rates of up to 200,000 samples per second per channel – enough to capture all acoustic and vibration events occurring in the vehicle in real time.

Signal Analyzer and NVH Software

Raw data from DAQ systems—millions of points per second—only becomes useful information after passing through specialized analytical algorithms.

The core analytical tool is the Fast Fourier Transform (FFT), which converts the signal from the time domain to the frequency domain. Instead of seeing a complex vibration curve over time, engineers see a frequency spectrum—a graph showing how much sound or vibration energy exists at each specific frequency. From there, identifying the source becomes intuitive: electric motor whining at 3,500 Hz, floor panel resonance at 80 Hz, or brake screeching at 8,000 Hz all show up clearly on the graph.

Modern, specialized NVH software offers a wide range of advanced analytical tools:

• - Order tracking: Monitoring frequency components synchronized with engine RPM or wheel speed, particularly useful for NVH powertrain analysis.
• - Transfer Path Analysis (TPA): Analyzes the contribution of each vibration path to interior noise – the most important tool for deciding where to make engineering interventions.
• - Operational Deflection Shape (ODS): Visualizes how the vehicle's structure deforms and vibrates at specific frequencies, allowing engineers to "see" the vibrations instead of just reading data.
• - Sound Quality Metrics: Calculates sound quality metrics such as loudness, sharpness, roughness, and tonality – parameters that reflect subjective human perception rather than simply decibel levels.

Chassis Dynamometer & Shaker System

For NVH testing to be meaningful, the vehicle must be operated under controlled conditions. The following two equipment systems create those conditions right inside the lab.

The chassis dynamometer system allows the vehicle to operate at different speeds and loads without moving from the test chamber. Rollers placed under the wheels simulate road and wind resistance, while the entire measurement system operates normally. This is the only way to perform repeated NVH testing under the exact same conditions – something impossible when driving on real roads.

A shaker/vibration exciter system generates controlled vibrations that are applied to the vehicle's structure or components. There are two main types of applications:

• - Modal testing: This involves vibrating the entire vehicle or individual components at various frequencies to determine the natural frequency and vibration pattern (mode shape). This data is fundamental for designing a vehicle that avoids resonance in dangerous frequency ranges.
• - Road simulation: Uses multiple actuators mounted on the suspension system to recreate the vehicle's movement on different types of road surfaces - smooth asphalt, gravel, potholes - with pre-programmed amplitude and frequency based on real-world road data.

Laser Vibrometer Camera System

This is advanced technology that allows vibration measurement without physical contact with the surface being measured – an ideal solution when the surface is too small, too hot, rotating, or too sensitive to mount an accelerometer.

A Laser Doppler Vibrometer (LDV) projects a laser beam onto a target surface. As the surface vibrates, the reflected light undergoes a Doppler frequency shift according to the surface's velocity. The device measures this frequency shift and calculates the vibration velocity and amplitude with nanometer resolution.

A more advanced version is the Scanning Laser Vibrometer – which automatically scans hundreds or thousands of points on a surface structure with a laser beam, creating a complete vibration map without the need for any sensors. Visualizing the results in color allows engineers to see which points on the metal sheet are vibrating most strongly, thus identifying areas that need reinforcement or additional sound-absorbing material.

Acoustic Camera / Sound Source Localization System

When a car makes a strange noise and engineers need to know exactly where it's coming from, an acoustic camera is the answer.

An acoustic camera consists of an array of multiple microphones (ranging from dozens to hundreds) in a specific layout, combined with a regular camera to capture images of the vehicle. Software processes signals from all microphones simultaneously, calculates the direction of the sound using beamforming techniques, and overlays a color map onto the vehicle's image showing which points are emitting the strongest sound.

The result is a visual representation—almost a thermal image—of the noise, where red indicates a strong source of sound and blue indicates a quiet area. An engineer can, in minutes, determine that the noise is coming from the lower left corner of the car door, instead of spending hours searching by ear or a single microphone.

Summary Table of Cultural and Sports Equipment by Application

Trends in the Development of Cultural Center Equipment

The modern NVH lab is undergoing significant transformation in two main directions.

The first approach involves integrating NVH measurement into real-world vehicle conditions (on-board NVH measurement). Instead of just taking measurements in a lab, miniature devices are permanently installed on prototype vehicles, continuously collecting data throughout the test drive on real roads. The data is transmitted wirelessly to a processing center in real time, significantly shortening the development cycle.

Secondly, there is the application of artificial intelligence in NVH analysis. Machine learning algorithms trained on massive measurement datasets are capable of automatically identifying sound sources, classifying noise types, and even predicting the NVH level of a new design before a physical prototype is built – opening up the possibility of optimizing NVH right in the purely digital design phase.

Noise and vibration measurement equipment in an NVH lab are not isolated tools—they are an integrated system where each piece of equipment complements the others. From finger-sized microphones to multi-ton roller systems, they all serve a single goal: ensuring that every NVH engineering decision is built on accurate, reliable, and reproducible data.

In an industry where customer perception dictates product success or failure, investing in NVH measurement equipment is essentially a direct investment in the quality of the vehicle—and in the long-term reputation of the brand.

GPower Vietnam provides and advises on specialized NVH testing equipment solutions for the automotive and industrial sectors. From measurement microphone systems, accelerometers, and DAQ to comprehensive NVH analysis software – contact us for advice on solutions tailored to the scale and needs of your lab.