Promotion through radio has been a viable advertising option for nearly 100 years. Radio advertising is mostly local to the broadcast range of a radio station, however, at least three options exist that offer national and potentially international coverage. First, in many countries there are radio networks that use many geographically distinct stations to broadcast simultaneously. In the United States, some networks, such as Bloomberg (business programming) and ESPN (sports programming), broadcast nationally either through a group of company-owned stations or through a syndication arrangement (i.e., business agreement) with partner stations. Second, within the last few years the emergence of radio programming delivered via satellite (e.g., SiriusXM) has become an option for national advertising. Finally, the potential for national and international advertising has become more attractive as radio stations allow their signals to be broadcast over the internet and through smartphone applications.
In many ways radio suffers the same problems as television, namely, a mass medium that is not highly targeted and offers little opportunity to track responses. Yet unlike television, radio presents the additional disadvantage of limiting advertisers to audio-only advertising. For some products advertising without visual support is not effective. However, the restriction that radio is limited to audio-only advertising may be changing. This can primarily be seen in the form of internet access and mobile apps that not only allow radio stations to be heard but also enable audio ads to be supported by visual messages that appear on the screen of the device that is streaming the radio station.
It is important to note that commercial radio is not the only outlet for audio advertising. Advertising can also be inserted within audio podcasts as well as being embedded within audio content played on websites.