The studio rooms should be sufficiently acoustically isolated from each other and the surrounding non-studio spaces that use of one space is not compromised by noise emitting from another. In the building of suitable rooms, isolation is on a sliding scale dependent on the techniques employed, however there is a sizeable jump in the level of isolation available (especially at lower frequencies) when room-in-room construction techniques are used which drastically cut structure-borne noise transmission. As a result the method of creating such isolation structures is not one that lends itself to cost-cutting.
Having trapped all sound within each of the recording rooms, such sound (which in normal rooms escapes from windows, doors, ceilings etc.), rattles around the room, producing a cacophony of reverberation, rendering the room useless for any acoustic purpose. As a result, acoustic trapping must be applied to bring the internal ‘sound’ of the room back to ‘normal’ i.e. the reverb times across the frequency spectrum must be adjusted to a figure generally considered acceptable for the purpose for which the room is to be used.
The internal acoustics of control rooms will further be refined to produce an exceptional stereo imaging from the monitor speakers, allowing the engineer to hear the results of his/her endeavours as free as possible from room artefacts. This is taken a stage further in 5.1 ‘surround’ rooms, where surround sound imaging must be stable from all directions, not just the front of the room, and where there has to be an allowance for the presence of (at various times) unused surround speakers acting as unwanted tuned absorbers.
Typically, Control rooms will have a ‘flat’ frequency response, with a reverb time consistent across the frequency range that is slightly shorter than the typical domestic environment. In contrast, recording spaces will vary depending on the purpose for which they are to be used. Indeed the recording engineer uses the ‘sound’ of spaces as part of the palette of sound ‘colours’ with which he/she ‘paints’ a recording. The net result of this is that a good studio usually contains a range of different sounding acoustic spaces from which the engineer can choose. These will range from near anechoic (vocals, acoustic guitar), to heavily reverberant (drums, choirs, and again – acoustic guitar!).
The isolation shells will reduce the internal size of the rooms, so special attention has to be paid to the ergonomics of the rooms and the utilisation of space so as to maximise the working area. This is best served by careful design of the space allied with furniture designed to fit the room rather than off-the-shelf free-standing furniture.
The listening environment must be essentially quiet so that monitor speaker levels do not have to be turned up high in order to listen ‘over’ the background noise (Such practices result in listener fatigue and shorter critical attention spans when mixing).
In a recording room, where microphones are used, the problem is even more critical.
As a result, unwanted noise sources within the room (e.g. Computers, a/c etc) must either be removed or neutralised (acoustic cabinets etc.).
An isolated room is by it’s very nature totally airtight, fresh air ventilation is a must as the oxygen / CO2 balance in the rooms will otherwise soon change, leading to headaches, reduced attention span and worse…..
Also, isolated rooms are heavily heat-insulated, as the Rockwool used for sound trapping is similar to that used to heat-insulate houses. This – combined with the not insignificant amount of heat generated by the audio equipment means that air-conditioning is an essential. Indeed, even in cold climates such as the UK, most studio a/c systems are cooling (rather than heating) their spaces even in mid winter.
The background noise criteria mentioned above, mean that un-silenced ventilation, normal ducted, or on-the-wall ‘cassette’ a/c systems, are completely unsuitable for studio use. The correct way to ventilate and condition is to use an inherently quiet ducted split a/c unit, which introduces a percentage of fresh air in each cycle. This must then be passed through critically mounted custom silencers (commercial silencers are not up to the job). These silencers stop ingress and egress of external and a/c noise, and also allow more than one room to be fed by the unit without excessively compromising the isolation.
Whilst there are no specific regulations for commercial audio facilities, the new BB93 for acoustics in schools came into force in July 2003, and, whilst (as far as I am aware) this is only applicable if studios have regular use teaching children of school age, the criteria contained therein form a suitable base specification to which all studio projects should aspire as a bare minimum specification for a workable facility.
Many of the educational facilities for which we design studios are not, in fact, schools as defined in the Building Regulations. Universities, Colleges of Further Education and some sixth-form colleges do not have to comply with BB93. But by publishing, for the first time, definitive standards for studios in schools, the DfES has set a standard, which even those institutions should consider. Anyone designing a studio for a College or University to a lesser standard than that required for a school should, at the very least, be able to give a good reason for this. Ignorance of the criteria in BB93 will probably not be considered a valid excuse if at a later date it is found that the studios fall within the remit of the regulations.
Howard Turner has over 30 years experience in the studio business, and for the last 2 decades, his Studio Wizard Organisation have been at the forefront of the development of effective & affordable designs and solutions for studios. Further information: 07092 123666 web: www.studiowizard.com