whats that noise?

This big ol dandy is a 47 caddilac....I had it for about a year in 1957-8.....It was fun but just cost to much to drive it......some kids just don't learn....I had it for a few months before I discovered where the heater was....I did not think it had one but in the Fall I discovered a button I had not pressed yet.....low and behold two of em under the seats with great big fans ...what was that humming all about?....oh ...that's where the heater is.....duh......in 1958 I traded it on a 50 plymouth....