Callers cannot always hear when we use our Sennheiser headphone

SOURCE: dell inspiron 1520

Try uninstalling the software, then re-install it again and only plug the headphones in when asked to do so, this will enable the program to pick the headphones up and install the correct driver, if windows picks it up as new hardware and tries to install the drivers for it then it will not work correctly.

What version of vista are you using 32 or 64?

SOURCE: RS120 Can still hear TV when headphones are on

Ok.. first.. the simple thing is to go into your television menu and turn the television speaker OFF.
Then exit the menu and turn the volume up.. try your headphones now.

Next.. check the back of the TV for a FIXED AUDIO OUT.. plut your headphones into these outputs.. if you have these.. you can simply turn the set down.. and use the volume control on the headphones.

SOURCE: Can't hear callers on my mobile phone

Your handset thinks that you have headphones connected.
Make sure there is nothing stuck in the headset connector port, and make sure it is clean.
If thats not the problem, then it may be cured via a software upgrade or it may need a hardware repair.
Either way your gonna have to take it to a shop to be done, unless youve got the required equipment to hand.

SOURCE: Sennheiser Hd 205 headphones stopped working properly

Although I'm not an expert I'm not quite sure if armadillopic is right. I had the exact same problem and managed to overcome it by replacing the cable from the headphone to the mini-jack plug. I actually only had to renew the last bit of the cable but chose to replace the entire cable. I found out that when I bend the last part of the cable in the exact right position the strange high pitched sound that was going over the vocals went away and the vocals became much louder and clearer like they normally did. Perhaps you can try if this works for you as well? Just bend the last end of the cable in various kinds of positions (NOT TO EXTREME OR YOU WILL ONLY DAMAGE THE CABLE MORE!). Hope you are able to narrow down the problem to just the cable. Greetings!