A steerable suspension system having a composite axle beam. The functional materials can be used for the preparation of light emitting devices comprising fibers as light emitting elements. The adjustable-vehicle-related parameters may be determined by data entry, by simulation of the vehicle, andor by data processing, including processing ergonomic data for the driver. The module andor the speaker may be adjusted relative to the wearer in any of the anterior-posterior direction, the inferior-superior direction and laterally.