856 Chapter 29
scenes. Recent advances in digital reverberation, room simulation, and effects have, however,
added a new dimension to such productions, enabling a wide variety of environments to be
electronically simulated and added in at the mixing stage. The same is the case with musical
performances/recordings.
It is important not to make studios and control rooms too dead, as this can be particularly
fatiguing and even oppressive.
TV studios have to cater for a particularly wide range of possible acoustic environments,
ranging from the totally reverberation-free outdoors to the high reverberant characteristics
of sets depicting caves, cellars, or tunnels, with light entertainment and orchestral music
and singing somewhere in between the two.
As the fl oor of the TV studio has to be ruler fl at and smooth for camera operations and
the roof is a veritable forest of lighting, the side walls are the only acoustically useful
areas left. In general, these are covered with wideband acoustic absorption, for example,
50-mm mineral wool/glass fi ber over a 150-mm partitioned airspace and covered in wire
mesh to protect it. Modular absorbers are also used and allow a greater degree of fi nal
tuning to be carried out should this be desired.
29.3.1 Absorbers
Proprietary modular absorbers are frequently used in commercial broadcast/radio studios.
These typically consist of 600-mm square boxes of various depths in which cavities
are created by metal or cardboard dividers over which a layer of mineral wool is fi xed
together with a specially perforated faceboard.
By altering the percentage perforations, thickness/density of the mineral wool, and depth
of the cavities, the absorption characteristics can be adjusted and a range of absorbers
created, varying from wideband mid- and high-frequency units to specifi cally tuned low-
frequency modules that can be selected to deal with any particularly strong or diffi cult
room resonances or colorations, particularly those associated with small rooms where the
modal spacing is low or where coincident modes occur.
29.3.2 Resonances
Room modes or Eigentones are a series of room resonances formed by groups of
refl ections that travel back and forth in phase within a space, for example, between the
walls or fl oor and ceiling.