Loudness
The auto-loudness feature boosts low-frequency audio response in order to compensate for the inability of the ear to hear low-level, low-frequency tones. The auto-loudness compensation varies inversely with the volume control setting.At low volume settings, the low frequencies are boosted much more than at high volume settings.
UM6: For a description of the RPO Code(s) shown in this article, refer to the RPO Code List found at Vehicle/Application and ID RPO Codes