Comment by ecocentrik
7 years ago
3. The A/D converter used by your car stereo headphone jack is low quality and introduced sampling artifacts.
4. You have a high definition radio and were listening to a high quality digital signal over FM as opposed to an FM analog signal.
It's probably a combination of all of these.
There is no "high definition radio." In the context of FM radio the H stands for hybrid and the D stands for digital. The digital often sounds worse when you compare them. Less noise for sure, but synthetic treble, almost as bad as Sirius XM.
Digital radio is very very low bitrate. A good FM signal is superior.
FM is capable of the same frequency response as CD, and it's a purely analog signal. If you don't have interference, you are getting a very pure stream of audio. The station is also probably using CD grade audio, so most of that quality is preserved.
From an audio standpoint, FM is a pretty decent sound medium. It's going to depend on your equipment, signal, and if you are moving.