HD Radio, sometimes called high-definition radio, is a technology by which audio can be digitally sent over the air by radio stations in much clearer and rich-sounding audio quality than via traditional analog signal processing.

Currently, about 75% of the U.S. population is within range of at least one HD radio station. In Michigan, 39 AM and FM stations currently broadcast in HD, including most of the big stations in and around Detroit. (Go to www.hdradio.com for a list of HD stations by state.)

Because the sound is delivered as a digital stream, a special radio receiver is required. They typically sell from $100 to $600.

A side benefit to HD radio is that the radio can also display text information and, because the format is so compact, HD radio stations can multicast, or offer more than one program stream on its frequency.

For example, in Detroit, WNIC-FM (100.3) broadcasts its traditional adult contemporary format. But with multicasting, its HD2 Channel offers ballads and love songs as well. You won’t hear the HD2 station with a traditional radio receiver, but with a HD receiver, you can chose either stream. It’s like that all ocer the country.