# Microphones: Part 8 - Audio Vectorscopes

The audio vectorscope is an excellent tool for assuring quality in stereo sound production, because it makes the virtual sound image visible in the same way that a television vectorscope allows the color signals to be seen.

Fig.1 - The vectorscope was originally a modified CRT in which the left input deflected the beam 45 degrees left of the vertical and the right input deflected the beam 45 degrees right of the vertical. In phase test tones of the same amplitude produce a central trace, whereas an inadvertent phase reversal results in a horizontal trace.

Fig.2 - At a) the phase difference due to spaced microphones at one frequency causes an elliptical vectorscope display. At b) the effect of changing the frequency, but not the position of the source, gives a completely different phase relationship. The inter-channel differences with spaced microphones have little to do with the original sound image.

Fig.3 - a) The summing of left and right signals from spaced microphones in an attempt to create mono results in a comb filter - b) Poor microphone positioning picks up a strong reflection along with the wanted sound, giving the same comb filtering as in a).

# Transforms: Part 7 - Standards Conversion

The transform is a useful device that has some interesting characteristics. On one side of a transform we might have the spatial domain, for example data describing an image in terms of brightness as a function of position. On the…

# Master Control: Part 1 - The Four Missions Of Master Control

We begin this mini series with some history, the basic principles of Master Control and the evolution of centralcasting.

# Vendor Spotlight: Telestream

Telestream, based in Nevada City, Calif. (with additional offices in Westwood, Mass,), is a privately held company that supports customers around the world in the Broadcast, Professional Video Production, Education, Corporate and Military market segments. The company is celebrating its 2…

# Transforms: Part 6 - The Discrete Cosine Transform (DCT)

The Fourier Transform is complex in the mathematical sense, which means that each coefficient is represented by complex number.

# Transforms: Part 5 - OFDM

Thus far we have looked at transforms from a somewhat abstract viewpoint. In contrast, here we look at an application where transforms take center stage.