The same problem with Assassin's Creed, and the same solution. With this solution you cannot play Kane & Lunch:Dead Man, except reverting to default.
Solution:
Go to:
Control Panel
>>Sound and Audio Devices
>>>>Under Volume Tab
>>>>Speaker Setting
>>>>>Press Advanced...
>>>>>>>Performance tab
>>>>>>>Hardware Acceleration
>>>>>>>Change Hardware Acceleration from Full Acc. to Standard Acc.

Thats it. Happens to most games that supports DX10.

I had a similar problem the first time I played DMC4. A similar thing happened with Pro Evolution Soccer 2008 but in its case I couldn't hear the commentary.

Here's what I did... (similar to what has already been suggested but I didn't touch hardware Acceleration)

Go to:  Control Panel > Sounds and Audio Devices
- Then Speaker Settings > Advanced > Then under speaker setup change it to either Desktop stereo speakers or Stereo Headphones. You probably have it on 5.1 surround sound.

I did that and it worked for me. I started playing DMC4 again from the start and I can now hear everything they are saying.