App note from Texas Instruments on isolating DC and high frequency noise in audio using their automotive op amps. Link here (PDF)
Phone calls, emergency alerts, and music are just a few of the reasons that a high quality audio system is vital in automotive infotainment and clusters. Operational amplifiers (op amps) are one of the most common building blocks of automotive audio circuits. Many designers choose to incorporate op amps into their automotive audio circuits in order to increase audio performance. Higher order filters, which can be created through a combination of second order filters, attenuate noise more aggressively than lower order filters. Additionally, active filters remove the chance of unwanted interference with the audio signal.