The Goniometer, also known as an Audio Vector Oscilloscope, is an instrument that offers a complete image of the relationships within a stereo signal. It is a tool that shows the stereo separation signal measurement within the audio metering world. Its main task is to plot the signal on a two-dimensional zone so that the correlation between both channels becomes visually present.
The Goniometer offers intuitive and important information. Through its display, the user can get useful information regarding the audio levels for each channel. S/he can also understand the amount of stereo, its compatibility as a mono signal, and the frequencies of that specific signal. The most experienced users identify the arrangement of the mics after the signal recording!
The Goniometer: How It Works
The Goniometer has an oscilloscope with one input for the X-deflection and another one for the Y-deflection. In the Audio Vector Oscilloscope, the image is rotated in such a degree that, when the same signal is applied in the X and Y channels, it leads to a vertical deflection. When the signal is the same, but is in the opposite stage, the deflection leads to a horizontal deflection. What this means is that the Goniometer is capable of showing several simultaneous parameters in the stereo signal. You achieve a higher degree of mono compatibility when the bigger part of the vertical axis lies within forty-five degrees. If the curves begin to bend it means that there is nonlinearity between the two channels. In turn, this nonlinearity means that there is overloading in one of the channels.
About the Channels
The first thing that an audio technician does, prior to each session, is to adjust the equipment. It is essential that the output produces a vertical plotline. If one of the channels is inverted, the plotline becomes horizontal, resulting in a noise reduction of the mono signals. Because the signal tends to be dynamic, the persistence of a CRT display is a looked-for effect in goniometers. The best digital and software goniometers offer artificial and user-adjustable persistence.