Relationship Between the Physical and the Psychoacoustic Parameters of the Sound Field in an Automobile

A new method of measuring physical factors that prescribe the sound field of the vehicle interior has been used to evaluate the differences in the sound field for 4 types of two-channel loudspeaker systems, which are installed in the front part of the vehicle.

The physical property which prescribes the sound field inside the vehicle is related to the directional properties of the sound, such as lateral, forward and backward component of the early reflection sound energy.

Psychological experiments have also been conducted under the same conditions as that for the physical measurement, and then the correlation between the psychological factor and the physical factor has been examined.

The following conclusions have been reached:

1. (1)
   L/M (the ratio of low frequency sound energy vs. medium frequency sound energy) is highly correlated with spatial impression.
2. (2)
   F/B (the ratio of forward directional energy vs. backward directional energy) greatly contributes to the preference of the sound quality.
3. (3)
   L/R (the ratio of left directional energy vs. right directional energy) is highly correlated with the localization (left and right) of the sound image.
4. (4)
   Among the four types of two-channel loudspeaker systems, “mounted in the front doors” has a wide sound image and is more preferable in comparison with the other loudspeaker locations.