Analyzer View

This is the main view of Overtone Analyzer. In here you will see the current spectrum or spectrogram display. The Overtone Sliders are also displayed in here. Surrounding the Analyzer View are the Frequency Scale and the Spectrogram Time Scale. They can be turned on and off in the View Menu.

Selected Range

You can select a time range with the mouse. If you right-click into the view to bring up the context menu, you can zoom to the selected range. Also, during playback the selected range will be played in a loop.

Spectrum Display

The Spectrum Display shows the intensity or volume of the frequency components of a sound:

Figure 1: Frequency Spectrum

The frequency axis is shown in cycles per second (Hertz), and the intensity axis is shown in decibel (dB).

You can use the overtone sliders and the mouse curser to get a better reading from the scales. This image shows a test signal whose strongest frequency component is at 100Hz with an intensity of about -16dB:

Figure 2: Using sliders and cursor

The range of the intensity scale can be adjusted with the dynamic range slider. The range of the frequency scale can be adjusted with the scale range controls. All range sliders and controls can be found on the toolbar and on the options dialog.

You can select different color schemes and display types for the spectrum display in the program options.

Spectrogram Display

The Spectrogram Display (also called Sonagram) is very similar to the spectrum, but instead of a single spectrum, it shows a series of spectra over time. Here is a spectrogram of the same test signal as in the spectrum above:

Figure 3: Spectrogram Display

The intensity is now solely represented by the color of each point on the display. You could think of it as looking at a series of stacked spectra from the top. Of course, this image is not very interesting because it shows the recording of a constant signal. The real use of spectrograms is to see how a sound changes over time. Let's look at a simple example. You can also listen to this sound with the link below:

Figure 4: Whistle

listen to whistle sound

In this example a whistling tone starts at around 1000Hz, changes to 2000Hz and then back to the original pitch. The bright blue line marks the fundamental frequency of this tone, while the fainter lines above are the harmonics.

Using the Overtone Slider overlay and the piano keyboard, you can relate the sung pitch to musical notes:

Figure 5: Whistle with slider overlay and keyboard

The tone starts at c and goes up by one octave. This image also shows that the second harmonic of a tone is also its first octave.