Abstract
An acoustic engine noise analysis has been made inside a SEAT CORDOBA (model VARIO) vehicle as a prior step to develop and implement a low cost active noise control system in order to attenuate the periodic engine noise. This analysis, made in the 1500 - 4500 rpm (50-150Hz) range, will determine the best locations for the control speakers and also for the microphones (close to passengers), where to produce acoustic silent zones.
The noise has been recorded at 5 cm from the car ceiling, in a grid of 20 x 9 elements (10 x 10 cm) in order to cover all the surface. A signal produced by an accelerometer, located directly on the engine body, was also recorded simultaneously with the acoustic noise. A processing software, developed with LABVIEW under Windows environment, extracts all the information required to do a good analysis. Different grid maps are presented for each analysis frequency, such as sound level map, accelerometer-microphone signals correlation and delay. In active control systems, the maximum sound pressure levels obtained are candidate positions to locate the control speakers and the maximum correlation values are candidate positions to locate the microphones (close to passenger heads).