NVH (noise, vibration, and harshness) testing and monitoring: review of current market segmentation, application spheres and technical solutions.

What is the NVH?

NVH (also sometimes referred to as N&V) is an abbreviation for noise, vibration and harshness. This method implies study, modification, and adjustment of the noise and vibration characteristics of the controlled structure based on its target parameters or intended use.

At the initial stage of this technology development and implementation, the NVH has been mainly used in the automobile industry for testing the noise and vibration characteristics of various vehicles and trucks. Noise, vibration, and harshness monitoring mainly implies control of noise and vibration characteristics, attributed to aerodynamic, mechanical and electrical parameters of the controlled structure.

Market segmentation, application spheres

At the early stage of its development, the use of NVH analysis was mainly restricted to the automobile industry. Nowadays it is possible to outline a variety of industries and spheres where the NVH research can be implemented for:

  • Structural elements and components downsizing
  • Noise mapping
  • Environmental noise level control
  • Modelling of building acoustics
  • Industrial noise and vibration level control
  • Development of power generating machinery
  • Consumer electronics
  • Design of industrial equipment

We can clearly see that the application sphere of the NVH analysis now encompasses a variety of industries and undergoes constant development in terms of research methods elaboration and improvement.

As for the original application sphere of the NVH analysis (i.e., the automotive industry), there occurred major changes too. Initially, the NVH method was mainly used at the design stage of suspension, engines, gear mechanisms, shock absorbers, sleeve cushions, and shock towers. Later on, as performance and durability of these vehicle elements has reached certain level, the NVH research methods became also applicable to noise and vibration reduction in terms of overall comfort of vehicle’s occupants.

This very shift has led to the development of new sound-absorbing materials and treatments, various expandable foams, and damping panels.

NVH monitoring: instrumentation

Configuration of the NVH testing and monitoring instruments varies depending on the parameters of the controlled structure, its dimensions, and purpose of the NVH implementation. However, it is possible to outline several types of measuring instruments, which are most commonly used for the NVH monitoring implementation:

NVH: scenarios of use, composition of measurement systems and test methods description

  • Control of vehicle admissible noise level

Nowadays there exist certain standards describing the admissible level of vehicle’s sound emission depending on the type and class of a particular vehicle. In most cases, the test for conformance of the vehicle to the applicable requirements is conducted in several stages (kerb weight, full and partial load) and at various speed levels. As for the configuration of the test system, it encompasses the following instrumentation:

FFT Spectrum analyzer (the required number of channels depends on the amount of the measurement transducers used)

Microphones (as a rule, two microphones are located in transverse position to the vehicle as it passes the control area)

Accelerometers (the accelerometers are used for the vibration level monitoring at the controlled area in the case if this control parameter is provided for by the applicable requirements)

PC with the software used for the accumulated data analysis (the PC with task-specific software installed is used for visual representation and analysis of the signals received from the FFT Spectrum analyzers).

  • NVH level control in the passenger compartment. In order to conduct noise- and vibration level control in the passenger compartment, the following instruments can be used:

FFT Spectrum analyzer (the required number of channels depends on the number of the measurement transducers used; the FFT Spectrum analyzer is connected to the PC for data transmission and further processing)

Microphone (the microphone is placed in the central part of the passenger compartment; it is also possible to use two microphones located in the are of driver’s and passenger’s seats)

Accelerometer – in the case of simple configuration of the system the accelerometer is mounted on the slide of the driver’s seat or between the front seats. In the case of a more complex configuration of the system, the accelerometers are mounted near the pedal box, steering rack, gear box or instrument panel.

PC with the software used for data analysis (PC with pre-installed ZETLAB Software used for visual representation and analysis of the signals received from the FFT Spectrum analyzers).

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