Possibly from here we all not know about the unique from yahoo logo Let us see carefully yahoo logo here:
Have you found the unique from the logo, surely not cause you have not involved mouse and speaker to find on the unique, so here the key: tries to enlarge your voice of volume speaker and points pointer mouse towards exclamation mark from yahoo! logo
Simply exclamation mark from the logo you can click and in click will heard someone voice who is yelling word Yahoooooooooooooooo!!!