Both charities say they want to raise the profile of hearing loss in the UK and boost funding for research into the problem.
The charities said deafness, hearing loss and tinnitus were "woefully underfunded" in the UK, citing figures that showed £1.34 was spent on hearing loss for every person affected, compared with £14.21 on sight loss and £21.31 for diabetes.
They said that the government invested £1.7bn in medical research last year and charities £1.1bn, but that research into hearing loss received a disproportionately small amount of this money, given the scale of the problem.
The charities hope that by combining their efforts they will begin to address the imbalance in funding for research.
Action on Hearing Loss, which last year changed its name from RNID, employs 827 staff and had an income of £37.5m in 2011/12. The charity also supports 24 research projects and 12 PhD studentships.
Deafness Research UK employs 14 permanent staff, had an income of £1.1m in 2011/12 and supports 11 research projects.
The charities said that no decisions had been made on what the merged organisation would look like or what its management structure would be. They said they expected to make an announcement on a final decision in the spring.
"Hearing loss is something that will affect most of us during our lifetimes, but biomedical research is hugely underfunded compared with other health conditions," said Paul Breckell, chief executive of Action on Hearing Loss.
Vivienne Michael, chief executive of Deafness Research UK, said: "There have been some major breakthroughs in recent years, but research has the ability to deliver so much more. Together we believe that we could deliver the increased awareness and funding needed to make this happen."