Radio is the classic channel for mass advertising in audio form, present today also in its digital and streaming version (podcasts, music services). It builds reach and awareness, and works well in local communication and frequent brand reminders. Its strength is the low cost of delivery and the fact that it keeps the listener company in the background, in the car or at work, which is why it is sometimes called a companion medium; its weakness is the lack of a picture and harder measurement of effect. (Compare: ATL, TV)