The recording level input monitor is useful during the early stages of the setup and tuning of your recording installation. There are three views: the waveform display, the VU-meter and a spectral display of the input signal. What you see is not what you have recorded but rather the direct signal input of your sound card.
The Waveform view shows a linear representation of the input signal and looks like this:
The VU-meter view shows a logarithmic (decibel) representation of the input signal and looks like this:
The VU-meter looks like the one used on professional tape recorders. It will allow you to calibrate the recording sensitivity of your multimedia sound card. While speaking normally into your microphone, tune the sensitivity with the volume adjustment utility provided by your card manufacturer. Make sure the visual indication goes only occasionally into the red area (risk of signal clipping). Also make sure you are not always recording at too low a level (blue area). Low-level recordings require extra amplification later in the process and because this process amplifies both the desired signal and the background noise, this could cause unnecessary background noise in your recordings. A good compromise recording level is when the visual indication spends a lot of time in the green and yellow areas and sometimes goes very briefly into the red one.
Use the volume control applet that came with your sound card (this is card dependent) to adjust the input sensitivity such that the monitor color bar usually stays in the green or yellow areas when you speak into the microphone. Short peak bursts in the red area are of no importance. Avoid staying in the blue area for too long; you would be recording at a too low level.
The spectrum view shows the frequency content of the input signal. It is useful to detect background noise or other anomalies. It looks like this:
The spectral content can be viewed in linear amplitude or dB energy mode, and the frequency axis can be linear or logarithmic.
The Monitor Sound Input command can also be activated by clicking on player button 
under the graph pane.