[Alfonso]

I only know bocina for car horn. I use altavoz for speaker. I wouldn't understand if somebody tells me bocina with this nuance, but DRAE reflects it (entry 7) for Cuba. It's really important to say where these words are said. This one is an example of very regional usage.
Anyway, I don't want to discourage you, David. It's a great idea to have some daily words. I will learn both, the English and the Spanish part of it.