Au­dio every­where you look and, of course, lis­ten : last year alone, 900,000 pod­casts be­gan their work and re­ceive our ut­most at­ten­tion. But be­sides that, ra­dio and mu­sic stream re­tail­ers in par­tic­u­lar are ben­e­fit­ing quite a lot. And ad­ver­tis­ing in au­dio for­mats is al­so prov­ing to be quite ef­fec­tive – as long as you get it right.