852 Chapter 29
on-site value (i.e., what is actually achieved). Great care has to be taken to the sealing of
all joints and to avoid short-circuiting panels by the use of wall ties or debris within the
cavities. Furthermore, where doors or observation windows penetrate a wall, particular
care must be taken to ensure that these do not degrade the overall performance. For
example, the door or window should have the same overall sound insulation capabilities
as the basic studio construction.
Studio doors should therefore be solid core types, and are frequently fi tted with additional
lead or steel sheet linings. Proprietory seals and door closers must be fi tted to form an
airtight seal round the edge of the door. Soft rubber compression or magnetic sealing
strips are commonly employed while doors are rebated to help form a better joint.
(Wherever possible a sound lock should be employed, i.e., two doors with an acoustically
treated space between, such that one door is closed before the other opened.) Other
methods of improving door insulation include the use of two separate doors on a single
frame, each fi tted with appropriate seals.
Control room windows may be either double or triple glazed depending on the
performance required. Large airspaces, for example, 200–300 mm plus, are necessary
in order to achieve appropriate insulation. Tilting one of the panes not only helps to cut
down visual refl ections, but also breaks up single frequency cavity resonances, which
reduce the potential insulation value signifi cantly. The reveals to the windows should also
be lined with sound-absorbing material to help damp out cavity resonances.
Window glass needs to be much thicker/heavier than typical domestic glazing. For
example, a typical 0.25-in., 6-mm domestic window would have a sound insulation
performance of around 25–27 dB (21–23 dB at 125 Hz), whereas a 200-mm void fi tted
with 12- and 8-mm panes could produce an overall SRI of 52 dB (31 dB at 125 Hz).
Special laminated windows and panes can also be used to improve performance.
Studios are frequently built on the box within a box principle, whereby the second skin is
completely isolated from the outer. This is achieved by building a “ fl oating ” construction.
For example, the fl oor of the studio is isolated from the main structure of the building by
constructing it on resilient pads or on a continuous resilient mat. The inner walls are then
built up off the isolated fl oor with minimal connection to the outer leaf. The ceiling is
supported from the inner leaves alone and so does not bridge onto the outer walls, which