Depending on how old the CD is, this is easily explained. Originally when they were introduced CD was considered an audiophile medium and thus the mixes of the tracks put on them contained a higher dynamic range. Today's CD's are often over compressed and thus sound louder at lower volumes. It's the same trick TV stations use when loud commercials come on over a quieter show.
2012 Titanium Sedan, Ebony Black - 400A, Luxury Package
Ordered: July 14 VIN received: August 19 Sticker: Sept 3 Build Date: Sept 10 Delivered: Sept 21