http://www.darkwood.demon.co.uk/PC/.....r.html#Digital

There's a lot of meters on here, but "Digital Level Meter" is my favorite of them.
If you're doing live streaming, using PC audio and audio from your mic, you really need to use this (at least on Windows, sorry I don't know what you'd use on Mac).

The reason is- the way your computer sounds on your own speakers, as well as the way your voice sounds to you compared to your computer speakers has nearly NOTHING to do with the volume levels going out on your stream.

For one thing, the playback from your computer is adjusted by the master volume control before it goes out the audio jacks, and its volume also changes based on your speakers' volume settings, or the model of headphones you are using.

When recording from stereo mix however, all the individual outputs (waveout, CD, microphone, line) are adjusted by the stereo mix volume instead. Which only programs capable of recording on your computer can hear.

So while you might hear audio evenly and matched to your voice volume, what your stream is hearing could be very quiet, very loud, quiet PC audio with loud mic audio, or loud PC audio and negligible microphone audio.

The level meter listens to "stereo mix" or whatever your recording source is set to on your system, and gives you a visual indication of how loud what it's recording is, relative to the maximum recording volume. That way you can adjust your audio, and your mic, so everything's at appropriate levels for your stream (and adjust your speaker/headphone volume accordingly so you can still hear it).

So basically - just make sure nothing is consistently driving the levels into the red zone, and anything you want to be at a "star" volume, is hitting the same volume as your voice. :p A few dB make a big difference, since it's a logarithmic scale.