NVH and automotive test facilities

Acoustic test facilities for the automotive industry: whole-vehicle semi-anechoic chambers, indoor pass-by chambers, powertrain and engine cells, and end-of-line squeak and rattle rooms.

• A vehicle semi-anechoic chamber measures interior and exterior noise and vibration on a 2WD or 4WD vehicle during run-up, coast-down and at steady speeds, including intake and exhaust noise, engine compartment noise and steering wheel and seat rail vibration.
• The manufacturer states that its vehicle semi-anechoic chambers meet the technical compliance of ISO 3744 and ISO 3745, and that they are typically designed to a 50 Hz cut-off using metal-faced anechoic wedges quoted at 0.99 absorption.
• A powertrain cell normally places two or four independent dynamometers outside the chamber, leaving only the engine and gearbox in the hemi-anechoic space. That is what lets one cell handle manual, automatic, CVT, dual-clutch and hybrid transmissions.
• An engine noise test cell shares most of its build with a vehicle chamber but has no chassis dynamometer. The manufacturer gives a typical cut-off of 125 Hz, with coupled exhaust extraction, independent ventilation and cooling, and a conditioned aspiration air intake.
• Indoor pass-by testing is more repeatable than an outdoor track because it is independent of the weather. A row of microphones is placed alongside the vehicle running on a dynamometer instead of moving the vehicle past fixed microphones.
• Shake and rattle rooms sit at the end of the production line, usually with a four-post hydraulic rig, and have to be isolated from the rest of the plant or the test picks up the factory instead of the car.
• Older chambers built with foam or fibreglass wedges are commonly refurbished to perforated metal-faced wedges rather than replaced like for like.
• All project work, supplied as an equipment and acoustic design package. No catalogue items and no price on the website.

Where this is specified

• Vehicle manufacturer NVH research and development
• Powertrain, transmission and brake development
• Pass-by noise testing for type approval work
• Minimum sound emission testing of electric vehicles at low speed
• End-of-line acoustic quality control
• Component testing such as seat track mechanisms and cabin climate systems
• Absorption and transmission loss testing of interior trim materials

Standards that define the requirement

• ISO 362 covers measurement of noise emitted by accelerating road vehicles; ISO 362-1 applies to testing on a certified outdoor track.
• ISO 362-3:2016 specifies test facilities for indoor testing of category M and N vehicles to a precision comparable with a certified type approval track.
• ISO 16254:2016 covers measurement of sound emitted by category M and N vehicles at standstill and low speed — the pedestrian safety question raised by quiet electric vehicles.
• ISO 3744 and ISO 3745 are the free-field sound power methods against which the chamber itself is qualified.

These are the documents that set the requirement. Naming one is not a claim that a particular supplied item is certified to it; test evidence is issued per project.

Product lines in this family

• Vehicle semi-anechoic chambers
• Indoor pass-by chambers
• Powertrain anechoic chambers
• Driveline chambers without acoustic treatment
• Engine noise test cells
• Shake and rattle facilities
• Listening rooms for vehicle sound quality work
• Acoustic cabinets for dynamometers and purpose-built test rigs
• Anechoic wedges, acoustic doors, acoustic windows and floating floors for test facilities
• Refurbishment of existing chambers and replacement of degraded wedges