I am a bit confused about the meaning of 'public'.
Does it mean that a radio playing in a workshop at the back of a shop, which could be heard by customers buying its products or bringing items for repair, counts as 'public', whereas a workshop on an isolated farm, where the radio would only be heard by people who worked there, or a secure warehouse that members of the public are not allowed in, would not require a licence?
If the only criterion is that a member of the public can hear it, maybe private houses with their windows open require a licence. And what about car radios?