2004 Lexus LS 430 User Guide - Page 279

AUDIO (c) DSP Control D Automatic sound levelizer D Positioning selector 20L358 20L359a When the audio sound becomes difficult to be heard due to road noise, wind noise, etc. during driving, push the "ASL" button. The system adjusts to the optimum volume and tone quality according to the noise level. While the automatic sound levelizer is on, "ASL" appears on the display. By selecting the listening position, the system controls the output timing of the speakers to allow sound to be heard evenly, creating the ideal music environment. Each time you push the "POS" button, the position changes as in the following and the letter displays for 6 seconds on the screen. ALL DRIVER FRONT REAR 261