Consultancy : NVH

(Noise, Vibration and Harshness)

Capabilities

Hybrid Ride Simulation

Advanced Transfer Path Analysis

Aero-acoustics

Sound Quality Engineering

Intake and Exhaust Development

Hybrid Ride Simulation

MIRA uses a hybrid approach to simulate vehicle ride behaviour. This approach uses standard tools, such as ADAMS and FE Nastran, to characterise each component with the optimal tool. In addition, the tyre models are rigid-ring models, validated by experimental data and the damper models are neural networks, capable of modeling non-linearities

Simulink is at the hub of this approach, integrating all the tools. It also incorporates the vehicle flexure to simulate effects such as shake predicting, through ride curves, the driver’s responses.

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Advanced Transfer Path Analysis

Generation of virtual TPA models to evaluate different design options and to cascade targets to system and component levels

Structural CAE model information is used to update TPA models

CAE hard-point stiffness Sound absorption and acoustic barrier CAE noise transfer functions
	Data can come from empirical or analytical sources GT-Power engine and exhaust model Empirical acoustic transfer function

TPA data can be transformed from the frequency to the time domain. Contributions from individual paths can be replayed for subjective evaluation

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Aero-acoustics

Sound Quality Engineering

As well as conventional microphones for measuring noise and narrow-band or fractional octave analysis equipment, MIRA makes extensive use of sound quality techniques. Vehicle noise is recorded using a binaural head and replayed through headphones to give accurate reproduction of the noise as perceived by passengers. This enables jury evaluation to be carried out of various vehicles or build conditions with no time delay between samples. In addition, the recorded noise can be manipulated to arrive at a target sound that customers are happy with. During the development process, various what-if scenarios can be assessed to find the optimum solutions to problems rapidly.

Subjective appraisals Jury evaluation Competitor evaluation Target setting Subjective/objective correlation SQ metric calculation Bespoke metrics Statistical analysis Niche vehicle tuning Exhaust and intake tuning

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Intake and Exhaust NVH Development

Air intake and exhaust systems can have a major effect on the impression of refinement given by a vehicle through contributions to the interior noise level and sound quality. MIRA supply a range of services utilising specialised equipment and techniques that can offer major benefits during intake & exhaust system development and modification.

Acoustic Modeling

As vehicle development programmes become more compressed and early prototype vehicle builds are phased out, the importance of reliable simulation data becomes increasingly important. MIRA can offer acoustic modelling of intake and exhaust systems in the time and frequency domains based on the system geometry.

LAMPS is a frequency domain acoustic modelling code developed by MIRA and Loughborough University.  It is based on a combination of plane wave theory and optimised finite element routines, and enables rapid testing of many design iterations for acoustic transmission loss.

GT-Power is a time domain engine simulation code used for performance and acoustic analysis.  It is used extensively by MIRA’s Powertrain and Emissions Department for virtual engine analysis and development.  It offers the facility to develop customised routines for the acoustic modeling of components such as superchargers.  GT-Power models can also be used to generate gas-flow forcing functions for FE or BE models of system components to predict shell-radiated noise.

MIRA has recently developed a co-simulation methodology for linking a powertrain model with an ADAMS throttle body model for a more accurate throttle response. 

Measurement Facilities

MIRA has a comprehensive range of test facilities for measuring the noise and vibration features of intake and exhaust systems in-vehicle, on engine rigs or as standalone systems.  These facilities include

In addition, MIRA has its own unique system for performing automated drive-by testing and source ranking.  This can be used for rapid confirmation of modeling results.

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Sound Quality Analysis

Our Sound Quality tools allow quick subjective and objective analysis of intake and exhaust noise to be performed for a large number of system designs without the need for protracted test work.

Base engine noise can be recorded using a binaural head system, or simulated based on the geometry of the engine.  Transmission loss spectra generated by acoustic models can then be used to filter the engine noise to assess the effect on orifice noise.

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