Why a soundproof recording studio needs ventilation
Ventilation and air conditioning, sometimes known as HVAC (the 'H' stands for 'heating') is a vitally important topic to study in conjunction with soundproofing. When a studio is sound proof, it is also air proof, unless steps are taken.
Ventilation and air conditioning are not synonymous. Ventilation means access to fresh air from outside the building, air conditioning means cooling and maintaining the humidity of the air that is already inside. An air conditioning system may provide ventilation, but many do not at all.
There are a number of problems caused by such systems:
- Noise caused by air turbulence within the ducts
- Fan noise transmitted through the ducts
- Noise in the structure of the building transferring to the ducts and being transmitted through them
- Fan noise transmitted through the metal of the ducts
- The ducts create transmission paths through the building
These are the solutions:
Turbulence is reduced by having ducts with a large cross-sectional area. This allows the air velocity to be lower and any remaining turbulence will be lower in frequency.
Any airborne noise can be reduced by the incorporation of plenum chambers. A plenum is a large space through which the air must travel, lined with absorbent material. The air temporarily slows down and allows time for any sound it carries to be absorbed. The ducts are also lined, bearing in mind that the absorbent material must not give off particles (like mineral wool does), unless the air is being extracted. Baffles are generally not used as they increase turbulence.
Noise that would otherwise travel through the metal of the duct is reduced by suspending the ducts flexibly, and by having flexible connector sections every so often to absorb vibration.
Noise from the fan that would otherwise enter the structure of the building can be reduced by mounting the fan on a heavy plinth, itself resting on resilient pads. Obviously, a fan that is intrinsically quiet should be used.
Studio ventilation and air conditioning systems should be installed by contractors who have experience in doing this in a studio environment. Otherwise it is likely that the result will not be satisfactory.