m|multimic

Microphone array
for spatial level averaging at the driver’s head

The microphone array m|multimic is used for reproducible measurement of the sound pressure levels in the spatial area of a head on seats in motor vehicles. The spatial averaging over six microphone positions, which are acoustically independent of each other but still relevant for perception, is of particular importance for the frequency range above 500 Hz.

Applications

Typical applications of sound pressure measurements on seating positions in the vehicle:

dynamometers for recording rolling and engine noises
electromobility – comfort measurements for electric drives
engineering of mechatronic components, including ventilation noises, actuation noises
quality assurance – end-of-line testing
tunnel passages
acquisition of acoustic sound signals
laboratory setups

Product description

Up to now, single microphones, microphone pairs, headset microphones or artificial heads have been used to measure the sound pressure in the area of the head positions in vehicles. The reproducibility of the measurement results proves to be extremely difficult in the medium and especially in the high-frequency range, since the measured sound pressure depends on the exact position of the microphone. The strong local dependency of the sound pressure results from the given properties of the sound field, which is characterized by the random crosstalk of many sound waves. In addition, there are deviations due to the selected seating position, the position of the backrest and the mounting of the microphones. The solution to this problem is called spatial averaging.

For this purpose, a special microphone array was developed that meets the special requirements in the vehicle and optimally positions as few independently acting microphones as possible. The volume covered by the individual microphones corresponds approximately to the range of possible ear positions of people of different sizes and their different head positions. The required number of microphones and their positions were optimized by correlation functions in the head area determined from vehicle measurements in order to ensure the lowest possible sound variance of measurements.

Advantages

Fast and reproducible positioning of the array through an integrated height and angle scaling on the vehicle seat.
Utilization of six commercially available ½-inch measuring microphone types, attached via quick-opening clamp fastener, connected with only two cables to a measurement front end.
Reduction of the confidence interval of the sound pressure by optimal spatial averaging in the room area relevant for the assessment.
Accurate acoustic assessment of vehicles even in the medium and especially in the high frequency range.
Secure fastening of the m|multimic on the seat via holders for lap and shoulder belt.