Esta informação foi encontrada na rede de suporte do Skype por cedarviola. Eles apontam que a opção ainda está lá apenas "escondida".
If you look on the Call Window, and if you move your mouse into it, you will see a bunch of options magically appear at the bottom. One of these toward the right, looking like a pipe organ or something equally obscure, is an icon representing "Call Quality Information". If you can manage to click on this icon while it is visible, then you will be treated to a non-standard, immovable tabbed dialog that gives you a bunch of wonderful options. This dialog will probably pop up right in front of the video image but do not let that slow you down. Stop and read the options at the top, like Microphone, Speakers, Webcam, Computer and Connection. Then try to remember what you were looking for.
In your case it's probably Speakers. It will probably tell you that your Speakers seem to be Working Fine. Ignore that. Then look around for a slider bar with a blue button. If you grab that blue button with your mouse then you can simply adjust the volume and listen to your friends voice in blissful comfort.