does he watch the TV, or is it the noise?

we almost never have the TV on at our place, but we have music on a lot of the time - a mix of it ... pop, classical, Christian, rock, alternative ... a bit of everything, and DS responds well to it.

also, it's not strange at all for your 16 month old to only stay interested in an activity for 15 minutes - that's ok! and that's part of the hard work ... having lots of different things to do.

I second getting outside with him - whether it's the yard (even just him playing with leaves while you hang up some washing), or drawing with chalk on the driveway or going to the park, or walking the dogs with DS in the pusher, or a trip out - the library or a cafe or the shops or the pool - just for a change of scene.

I know I personally feel a lot better if I've got out of the house at least once a day!

And as your DS plays, watch how he's progressing from one activity to the next - which might help you to plan some activities for the next session .... eg: I might put out a tub of blocks, a dump truck, some books and then some cuddly toys. Because no matter where he starts, he can go from playing with the blocks (stacking and unstacking etc) to putting things into the truck and taking them out of the truck, to moving the truck around, and playing with the toys and books intermittently ... so those items could well keep him occupied for an hour or more, and even longer the more I interact with him while he's playing.