Pass-by Chambers

Vehicle pass-by noise tests are conducted according to the international standard ISO 362, which quantifies the noise emission of a vehicle in an urban traffic environment, by testing on an outdoor track.

Traditional field pass-by measurements are still the only way to certify a vehicle for exterior noise emissions during operation, but an indoor pass-by test provides an extremely powerful and repeatable method of troubleshooting exterior vehicle noise in the controlled environment of a hemi-anechoic chamber.

Instead of making the test vehicle pass two stationary microphones, indoor pass-by measurements place a row of microphones alongside the test vehicle whilst running on a chassis dynamometer and accelerated in the same way as it would be for a traditional pass-by measurement.

IAC Acoustics has designed numerous hemi-anechoic pass-by chambers for automotive manufacturers across the world. Due to the low frequency noise generated by a combustion engine, IAC Acoustics Metadyne® anechoic wedges offer the perfect solution to achieving a suitable testing environment.

New ISO Standards

ISO 362-3 Measurement of noise emitted by accelerating road vehicles

New developments to the ISO Standards are helping to ensure consistency across the latest vehicle tests.

Exterior noise measurement approval to the current ISO 362-1 standard must presently be carried out on certified outdoor test tracks.

Due to environmental influences, these traditional proving grounds do not give the consistency required by the increased demands of the motor industry.

Sound emitted from a vehicle should be tested under controlled conditions independent of weather and other environmental factors.

The forthcoming ISO 362-3 gives the specifications for test facilities to achieve a precision comparable to a certified type approval test track, thereby allowing indoor testing. 

ISO 16254 Measurement of minimum noise emitted by road vehicles

With the advances in electromotive vehicles, the minimum sound level emitted is of concern for pedestrian safety.

ISO 16254 is in preparation by the relevant ISO committees to provide a method to measure the minimum noise emission of road vehicles, as well as to quantify the characteristics of any external sound-generation system installed for the purpose of conveying acoustic information about the approach, presence and/or departure of the vehicle to nearby pedestrians.

All IAC pass-by chambers conform to the current drafts of these standards and will allow measurement of noise emitted by an accelerating vehicle and the measurement of the minimum noise emissions.