Testing : NVH

Proving Ground

Vehicle Semi-Anechoic Chassis Dynamometer (VSACD)

Engine Noise Test Cell (ENTC)

Anechoic Chamber

In-vehicle Data Acquisition and Processing

Sound Quality Analysis

Experimental Modal Analysis

Vehicle Subsystems Testing

Legislative Test Services

Facilities Specification

Consultancy

Proving Ground

The MIRA proving ground has a range of tracks and road surfaces suitable for NVH testing ranging from typical motorway surfaces through smooth and coarse surfaces to unmade roads and cobbles.

Vehicle Semi-Anechoic Chassis Dynamometer (VSACD)

The VSACD enables interior and exterior vehicle noise testing to be carried out in a controlled and repeatable environment without the interference of ambient weather conditions. It is particularly suitable for Powertrain related noise development including final-drive, engine intake and exhaust systems. The facility also enables development changes to be made to the vehicle for the purposes of problem investigation that would not be possible anywhere else.

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Engine Noise Test Cell (ENTC)

The ENTC allows an engine and gearbox to be run throughout its full operating range in a semi-anechoic chamber allowing accurate radiated noise measurements to be made. This allows the engine as a noise source to be developed in parallel to the whole vehicle, greatly speeding up the development process.

Anechoic Chamber

The anechoic chamber allows static vehicle or ancillary measurements to be made in an anechoic environment. This is particularly useful for ancillary component development or vehicle Noise Transfer Function measurements.

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In-vehicle Data Acquisition and Processing

LMS Test.Lab based data acquisition

5 in-vehicle systems
Total of 120 channels available

Specialized instrumentation

High temperature
High sensitivity

Binaural HEAD

Accurate reproduction of measured sound

Signature Analysis

Broad band/narrow band frequency analysis
Structural Analysis
NTF/VTF
Modal

Data Acquisition and Processing

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Sound Quality Analysis

A question of noise level or the sound quality?

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

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.

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Experimental Modal Analysis

MIRA has extensive experience of modal analysis techniques for vehicle bodies and systems.

This enables theresonant behaviour of systems to be optimised such that no significant resonances are present in the normal operating range of the vehicle.

Vehicle Subsystems Testing

MIRA has developed various specialised test facilities and measurement techniques for investigating subsystem noise issues in isolation. These include alternators, power-steering systems, compressors, etc. The systems can eitherbe motored in isolation or within the vehicle engine bay as shown above. The dynamic stiffness rig at MIRA is used to meassure the dynamic properties of elastomeric components such as enginemounts and suspension bushes.

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Legislative Test Services

Pass-by Noise

MIRA has a drive-by noise facility that conforms to EC and ISO requirements. This enables homologation testing of vehicles to be carried out as well as exterior noise development. MIRA has long experience of drive-by noise testing and has developed robust techniques for source-ranking and development.

Outdoor Machinery Noise

MIRA can measure Sound Power according to the EU Directive on Noise Emissions from equipment used outdoors. -”For equipment subject to permissible sound power levels, a procedure consisting of an involvement of a notified body for checking the conformity with the provisions of this Directive in the design and the production phase is considered to be appropriate.”

From Article 12 of the Directive.

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 replayedthrough headphones to give accurate reproduction of the noise as perceived by passengers. This enables jury evaluationto 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.

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Facilities Specification

Vehicle Noise Test Cell (VNTC)

17 x 6.8 x 4m high
Cut off frequency = 90Hz

Chassis Dynamometer:

Dyno speed 0 – 200 km/h
Power Absorption 250 kW
Motoring Power 160 kW
Maximum Loading 4250 kg
Roller Diameter 1.6m
Control Parameters Speed, Load, Road Load Simulation

Dedicated instrumentation and data acquisition

8 channel FFT and 1/12 octave analyser linked to IDS NVision PC-based package
16 channel LMS workstation based analysis system
16 channel DAT recorder for off-line analysis and assessment
Sound Intensity Probe
Binaural Head Measurement

Engine Noise Test Cell (ENTC)

6.5 x 6.5 x 4m high
Low frequency absorption cut-off of 180Hz for normal incidence sound waves
Temperature controlled cooling systems for engine coolant, engine & gearbox oil, PAS fluid and intake air

Dynamometers