Until recently, television audio was distributed through a cheap speaker installed on the receiving equipment. Today, on the contrary, television is also distributed in surround audio systems and in DTV 5.1. From an acoustic point of view, most television programs have a good ambient sound relative to dialogue and other critical audio sources. This noise masks the failures of the ambient sound so the acoustic criterion for most television studios is not as demanding as it would be in music production, in which the listener does need to experience the instrumentation and voice without the intrusion of another sound, in addition to music.
Although it is possible to apply acoustic systems and treatments to improve any problem in a given situation, structure or production space, in the long run it is always prudent to avoid a noisy place and eliminate the source of noise.
This approach, of finding practical solutions, is very important when you consider the costs and risks involved in building television production studios. Excessive investment in poor places and low investment in suitable places can impede the marketing and effectiveness of your study. With the help of experienced professionals, even modest venues can have the right acoustic environments at very reasonable costs. It is important for the study operator to ask very simple questions:
-What quality should my product provide?
-How much control can I have where it is currently produced? Can I choose my neighbors? Should I locate an existing space and pay to improve legacy problems? Can I choose a place to minimize my spending on improvements and use my capital in another way?
Will my clients wait to see certain types of treatments regardless of whether they need them or not? Will my clients emphasize performance?
When designing the acoustic aspect of a project, we care at first about the type of acoustic environment that is appropriate for the various spaces: studios, control rooms, etc. This is what we call the Design Criterion. The criteria are divided into two fundamental components: sound isolation (ability to contain noise inside or outside a space) and the response of the room or acoustics (how the room "sounds").
Insulation problems
There are many spaces, associated with television production, in which it is critical to apply appropriate acoustic design criteria, either to keep project costs within normal parameters or to achieve the desired functionality. Below, you can see some typical criteria for those spaces based on their function (See Table 1)
The criterion is expressed in terms of NC Noice Criteria or Noise Criteria. The NC is expressed as an average of the industry's normal frequency spectrum; the higher the NC, the noisier the space. These criteria determine the ambient (background) noise in a room that is acceptable for space as a graphed curve of decibels above octave band frequencies. These frequencies range from 63 Hz to 8000Hz. Once the criteria are established for a specific space, the appropriate construction must be specified to meet the requirements. If the space (or spaces) are to be installed in a previously existing construction, ambient sound readings should be taken to establish the background sound that is produced in the space from existing sources. If it is a new construction, the ambient sound reading should focus on specific sound sources that affect the design such as aircraft routes, street traffic, railroads or any other major source. In both cases the difference between the existing NC (ambient noise) and the required noise will define the required Transmission Loss or TL (Transmission Loss). TL is the measure (in decibels) of how much sound energy is reduced in transmission through materials. To achieve the desired TL, architects rely on measurements of building elements from the Sound Transmission Class (STC). The STC is a numerical measurement of the loss of airborne sound transmission. This number is established through measurement procedures established by the ASTM (American Society for Testing and Materials). The higher the number, the greater the loss of sound through the construction and the quieter the space, once installed.
The result of the above analysis will determine the type of construction required to achieve the necessary insulation set out in the criteria. As architects, we always strongly recommend hiring the services of an acoustic consultant to help establish the criteria with the client, measure and recommend types of construction that meet the desired insulation. In all cases, the architect will take into consideration that sound insulation must be applied uniformly and proportionately for it to be successful. I often like to refer to this as the "acoustic performance chain"; a weak link in design or execution can lower construction performance to the level of the weakest link. This issue is very critical when TL requirements involve disconnected or isolated constructs.
Isolated construction is normally associated with the construction of studios and recording spaces. When typical or average conditions occur, the design criteria require mechanical isolation of the interior surfaces of the structure space, a decisive contributor of ambient noise due to the structural vibration of a large number of sources such as air conditioning equipment, human trafficking outside the space and the impacts of other uses of the building or external sources such as low-flying aircraft. However, the use of an isolated construction may be required to meet even modest criteria in very noisy areas. I myself had an experience about it when I was working on renovating the Ed Sullivan Theater for the David Letterman show. The music mixing room was to be located in an area that has the New York subway running underneath. Even after providing all the isolation was practical, a low hum was still perceived.
A typical completely insulated construction is very expensive and involves the construction of an insulating floor above the structural floor, of walls lined above the insulating floor that do not attach to the attached walls of a space and a ceiling hanging from the structural ceiling by means of insulators. Many times it makes sense to resort to hybrids (where the isolation of one or more elements is omitted) such as when an isolated soil is omitted because the structural table has sufficient quality and there is no substantial vibration (such as that of a railway, for example).
An important component involved in the construction of sound retardant spaces is doors. Doors have an inherent potential to be the weak link of acoustic separation. It is not practical to manufacture the doors as heavy and thick as the walls; certainly, they must be operational which means that they must have hinges where they open and thus allow possibilities for sounds to sneak in, which does not happen in the construction of walls. There are several options depending on the application and size of the doors; however, an important aspect is to make the door operate as close to the acoustic wall as possible. For this to occur, the door, regardless of its construction, must be properly sealed by means of the gaskets in such a way that, when the door is closed, no sound inputs occur.
