Intended for use on soundstages and at optical transfer and
film QC facilities, the 737 reads the non-equalized outputs of a
cinema processor or mixing console. It can evaluate anything
from a trailer or commercial to elements of a feature’s complete
soundtrack for comparison purposes, and alerts mixers to the
potential for audience complaints about loudness levels when
the film is played in the cinema.
The 737’s operation is based on the measurement technique
known as Leq(m), developed by Dolby Laboratories after
extensive research into the perceived loudness of film
soundtracks. Unlike conventional audio meters such as VUs
and PPMs, the 737 monitors loudness over time—for the entire
length of a trailer, scene, or complete feature—and mimics the
varying sensitivity of the human ear at different frequencies,
taking particular note of those that are most annoying.
The 737’s measurement is displayed in decibels that can be
interpreted as an “annoyance factor” number. On material with
an occasional loud sound, the number will be relatively low,
while on material with loud sounds sustained over time the
number will be high.
In the 737, its six input channels are followed by weighting filters,
a true averaging power meter that can be started and stopped
remotely, and a trip circuit that indicates a preset maximum level
has been exceeded. In addition to showing measurement results
on its front panel display, the 737 can drive an external moving-
coil meter or chart recorder.
Use of the Dolby®737 meter has contributed to the adoption of
loudness standards for trailers and commercials in most areas
throughout the world, a reduction in the number of audience
complaints, and an improved moviegoing experience.