You’re drip-feeding us information. He’s depressed, he’s going deaf (but not too deaf to hear you singing quietly?)...
So, here’s my take on the situation. He’s got a bit of a short fuse at the moment for various reasons, and with someone singing quietly, but next to him on the sofa or certainly close enough to hear, he can’t hear the TV. It was rude of him to say what he did, but I think it might have been slightly insensitive of you to be cheerfully singing while he’s depressed and watching the box. Who sings on a whim while others are watching TV? Annoying people, that’s who. Especially to someone overly sensitive due to their circumstances.
Side-not: going deaf often makes differentiating sounds difficult. Therefore, despite the TV being cranked to 11, if someone is generating noise elsewhere, it can often become a big old mess of sound. I used to be able to listen to people in a noisy pub. Now I really struggle.
Conclusion: you were both rude and you need to cuddle more!