Same problem fixed.
I just wanted to let everyone know that after reading multiple forums, etc, this one finally helped my solve the problem of crackling sound. I tried almost everything listed previously in this forum on my brand new Lenovo Ideapad Y450 (nvidia graphics card, realtek high def audio, etc) running windows 7. The last thing I tried was to change the advanced power settings in control panel. Under processor power management, I changed the minimum processor state to 100%, like previously mentioned in this thread and the popping/crackling sounds went away and stayed away. I then tried various settings to see what would happen. At minimum processor state of 30%, the noises came back, but anything above 40 and I had no sound problems. THIS WAS A SOLUTION FINALLY!!! Thanks to those who posted and try this if you have not already!