Reduction of Comb-Filter Effects by Alternating Measurement Orientations in Automotive Environments

Inhalt:
Loudspeakers in car cabins often are installed in positions primarily regarding design aspects. Acoustical aspects are mostly subordinate. For this reason loudspeakers frequently radiate against a window, the dashboard or the rear shelf, also a radiation to the floor room is common. Acoustical reflections at short distances causing interferences of direct and reflected sounds are the main reason for comb-filter effects at the listening position. For the measurements in this work two stimuli were used: a pseudorandom pink noise, recursively averaged over 15 seconds, when the measurement position was changed, and a sine sweep when the position was fixed during the measurement process. Both, microphone movements and head movements, lead to a robust averaging of the measured magnitude response, reducing significantly both the variations in the response and the comb-filter effects in the car cabin. Frequency responses measured by the process described here require less filtering effort to equalize the loudspeakers in the car cabin.