INERCO Acoustic develop a system of measuring the level of sound power output of engines for the automotive industry for VALEO Spain

  

VALEO Spain has commissioned INERCO Acoustic to design, manufacture and install a semi-anechoic chamber (with an anechoic area) within its factory to allow for the measurement of acoustic output from their engines from the automotive sector.

 

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Semi-anechoic chambers reproduce “free field” conditions, ie; without reflections from walls or the ceiling, only from the ground, such as when we are in an environment that has a very low level of background noise allowing the measurement of engine noise without any external noise contamination or interference.

The sound insulation is designed using a "box in box" system that allows for high levels of acoustic insulation and low levels of vibration. This technology consists of the construction of a floating concrete structure supported on resilient elastic pads - INACUSTIC SA300 / CT, an acoustically insulated roof support - TCH-72 joined to the acoustically insulated floor and ceiling supports - TD-63 and TD-57; There is also a naturally integrated ventilation system - INASIN acoustic baffles, acoustic grommets, a large INADOOR acoustic door and an LED lighting system. The acoustic treatment comprises of polyurethane foam wedges 34 cm in length (roof, walls and floor in the anechoic area) and a ceramic floor in the semi-anechoic area.

The final characteristics of the semi-anechoic chamber are:

  • Interior Dimensions of 6.1 x 2.95 x 2.18 m
  • Cut-off Frequency (1,0,0) = 28 Hz
  • Semi-anechoic characteristics from 160 Hz.
  • Background noise level in the anechoic area approximately 22 to 24 dB
  • Background noise level in the semi-anechoic area approximately 25 to 29 dB

 

These features allow VALEO to acoustically characterise their engines according to the following regulations:

  • UNE-EN ISO 3745: 2012 Determination of sound power levels and sound energy levels of noise sources using sound pressure acoustics. Precision methods for anechoic chambers and semi-anechoic rooms.
  • UNE-EN ISO 3746: 2011. Determination of sound power levels and sound energy levels of noise sources using sound pressure acoustics. Precision method using an enveloping measurement surface over a reflecting plane and thus, further develop quieter engines.