When you left-click on the volume control icon in the notification area, a miniature volume control appears. If you have music playing, you will see two different volume levels whose heights change with the volume of the music—one gray and one green. What do they mean?
The gray bar represents the volume the music would be at if the volume slider were set to maximum. The green bar represents the actual volume of the music after applying the volume control at its current level.
OK, so why display the two different levels?
The audio folks learned that the volume control is the starting point for most users when troubleshooting the "I can't hear anything" problems. So they wanted to include the most common diagnostic information in an unobtrusive manner. While perhaps not entirely obvious at first, how this data is presented makes sense once you play with it for a few seconds.
So let's look at some scenarios.
Common reason #1 for no sound: Nothing is actually playing. This happens, for instance, when the user has forgotten to click Play. The clue for this is that the volume control slider doesn't show any moving bars at all—neither green nor gray. Your speaker is silent because you're not actually playing anything.
Common reason #2 for no sound: The volume is turned down too low. When you see the gray bar moving, that tells you that, well, something is playing, but the green bar is barely visible because your volume is set so low that the final result is a whisper. If you slide the slider upward, the green bar should get bigger and your music louder.
Common reason #3 for no sound: The speakers are not plugged in or the physical volume knob is set too low.
The gray bar is moving, the green bar is moving (and is a decent size), but you still can't hear anything. The computer thinks it is playing music—look at all that color and motion—so the next thing to look at is the connection between your computer and your speakers. Are the speakers plugged in? Did you plug them into the line-in jack by mistake? Is the volume knob on the speakers turned up sufficiently?
The audio folks on the Windows Team have a very difficult balancing act to manage. They need to make the sound experience simple for beginners who just want the sound to work (when they use cheap speakers and watch funny online videos of cats) while still satisfying the hard-core audiophiles (when they play back lossless audio recordings over expensive stereo systems). If you tinker too much to get those Internet videos to sound better (for example, automatically fixing volume levels), you end up alienating the audiophiles. As a result, a lot of potentially useful features are off by default to avoid upsetting those who take their audio playback very, very seriously.
By the way, if you want to turn on one of the potentially useful audio features, go to Control Panel | Sound | Playback | Properties | Enhancements and turn on Loudness Equalization. This tells Windows, "I want to set my volume control just once to a comfortable level and never touch it again." Then it doesn't matter whether you're watching recorded TV, watching a DVD, listening to a CD, or just being interrupted by a Windows beep—Windows will play them all at that volume. Note, however, that some programs do their own loudness equalization, and too many cooks can spoil the broth—or, in this case, degrade the signal quality.
Of course, many of the hard-core audiophiles would explode if the loudness equalization feature were on by default. "How dare you touch my finely tuned audio samples!"
I want to give a special thanks to Larry Osterman, Steve Ball, and other members of the Windows audio team for unwittingly providing the raw material that went into this article.
Raymond Chen's Web site, "The Old New Thing," and identically titled book (Addison-Wesley, 2007) deal with Windows history and Win32 programming. He listens to music on cheap speakers.