How do I get my dog to stop barking at me?

She is 14 and a bordercollie/blue heeler and only developed this habit recently. She does it when i am sitting at my computer or watching the tv, or focusing intently on something other than her. It started as just a groaning that she would do. Staring at me and groaning to get my attention. And it has progressed past that. From the groaning, to a whisper bark, to a slightly louder but still quiet bark... to a half bark and now she is really loud and it echoes off the walls. She doesnt do it in succession, but makes whatever noise, and waits a moment for me to respond. if i don't respond to her she will just keep doing it and get progressively louder