Handbook for Sound Engineers

VI Meters and Devices 1007

unique tool showing all the important parameters of a
surround signal at a glance. It gives detailed information
for all individual channels as well as the overall effect
of the mix.
The visual display of the Surround Sound Analyzer
provides level and phase relations of all channels. The
dynamic response of the display elements is a direct
representation of the acoustic image so the balance of
the surround sound can be observed.
The volumes of the four channels L, R, sL, and sR
are displayed as diagonal white level bars originating
from a common center point. Their tips are connected
through cyan lines. The square formed by this figure,
the total volume indicator (TVI), is a direct measure of
the total volume and the balance of the acoustic image.
The curvature of these lines shows the channel corre-
lation, positive values through an outward deflection
(roof), negative values through an inward deflection
(funnel).
The volume of the Center channel is indicated by
another upwards-pointing level bar with yellow
connecting lines, showing the perceptibility and domi-
nance of the Center in relation to L and R.
Direction and width of front, side, and rear phantom
sources are represented by lines between the loud-
speaker symbols, called the Phantom Source Indicators
(PSI). Their color changes with channel correlation. A
separate correlation indicator for the two surround chan-
nels is available at the bottom of the display.

A cross representing the dominance vector indicates

the position of the subjectively perceived center of

gravity of the mix.

The Surround Sound Analyzer displays a

correctly-scaled graphical representation of the relative

volumes in the surround sound field. The interaction of

levels (volume or sound pressure level) and the correla-

tion of all channels in the production of the overall

surround sound are displayed graphically.

The display in the Surround Sound Analyzer can be

set to correspond to the volume or the reference sound

pressure level by calibrating the instrument and the

studio monitoring equipment accordingly. The axes of

the 45° coordinate system use a dB volume level or

dB-SPL scale and have a reference mark that is also

displayed in the volume level and SPL displays in the

peak program meter of the instrument. The balance

between the Center channel and the L and R front chan-

nels is critical for all surround sound productions. The

Center channel is displayed with its own display

elements to show the volume differences between the

Center channel and the L and R channels.

In addition to the signal level, the correlation level

(and aligned to that the generation and the location of

phantom sound sources) is important for multichannel

sound productions, primarily in relation to downmixes

or possible sound-faking erasements when generating a

mono signal. The correlation level of the sL and sR

surround channels is also important. Highly anomalous

Figure 26-13. Block diagram of a Dorrough loudness monitor. Courtesy Dorrough Electronics.

Differential

amplifier

Peak

detector

and hold/

LP filter

Filter

Precision

rectifier

Reference

generator

Summing

amplifier

Linear-

logarithmic

convertor

Linear-

Logarithmic

convertor

Power supply

Dot

LED

driver

Bar graph

LED

driver

LED

array

V +V +V LED

Left

Right

Differential

amplifier