Wired for Sound

In power and communications systems, cabling is the essential physical layer. The same is true for sound or audio systems. Sound can include very fundamental and necessary services a commercial building may require—announcements, pages, background music, or advertising. You may want to learn about this technology yourself, or partner with someone already familiar with the business, to install the base for a sound system. It is important to partner with an expert who has similar expectations to yours and understands the business completely. The most significant difference between network and electrical work is the engineering. For a design-build project, applying rules to the design is the first step. For a bid response, submittals are the first step. Engineering support is critical to a successful outcome. Installation is not too dissimilar from other disciplines. However, the completion (i.e., testing and demonstration) proves the performance. Staying focused First, be aware of the type of work and skills-set you need. Work to consider resides in either the residential or commercial market. The residential end could range from very basic to part of a full multimedia installation. On the commercial end, projects could be basic sound system installations in schools, restaurants, supermarkets, shopping centers, or they could be full-fledged audio-visual setups for hotels, conference centers, training institutions, or entertainment venues. Potential installers also need to understand what makes that sound possible. It is important not to assume anything and to investigate any new type of work before performing it. Knowing the fundamentals of amplification, frequency, power and load factor calculation, and electromagnetic interference (EMI) are all very important to understanding and installing even basic sound. While this type of work is challenging, its requirements resemble those of data communications. For instance, both fields have different voltages and frequencies. Speed and distance dictate the type of cable used. There can also be a mixture of topologies, from “star” to “distributed.” When you begin an installation, find out what your customer wants delivered over their sound system. Consider asking the following questions while keeping the ideas listed below in mind: Is the sound system for pre-recorded music, paging, announcements, or live music? If it were strictly for entertainment, you would install the cable or wiring to amplify the best-quality sound for the audience. If it were for announcements throughout a school, for instance, there could be life and safety issues involved—an example would be requiring the system be “up” and available to broadcast emergency information at all times. What is the best mode for delivering sound from one end to the other? This is where the design and engineering enter—the cabling (shielded), type of conduit, amplifiers, microphones, and speakers, etc. The cabling and conduit are extremely important to the delivery of sound—without the right cable and proper pathways (conduits), the sound won’t make it from point A to point B. Stages of work The work is accomplished in two stages: Design, or documentation of the design and Installation. Install the shielded cable and metal conduit (versus plastic that does not protect against EMI). Remember to allow for adjusting the amplification, because the area may be larger as opposed to smaller, and people will need to hear and understand the speaker throughout that space. There may also be recorded music to play over speakers, and those signals have to be handled differently to make them understood by the human ear. An installation involves use of the proper cable, knowing what distances equal what speeds, understanding how many speakers can be accommodated on a run of what distance, and how to accommodate various voltages. Installers must plan to provide system setup, performance documentation, user training, and after-installation service. There are always questions about operation of all, including the simplest, of systems. The keys to success are quantifying the system and defining its outcome. The success of a public address system is not just hearing the spoken word from the microphone, but more importantly, understanding it. This is most problematic with a system that is improperly designed, installed, or set up. Just as in data communications, the physical layer has to handle the application (data transmission); in sound, the physical layer has to be capable of delivering that application (sound). Since this work seems similar to data communications, an installer must recognize that there are rules by which this work is done. The rules are similar to data “performance standards” and must be learned. Understanding electrical power or data communications standards is not enough. If you are interested in getting educated in this technical area, look into the certification provided by National Institute for Certification in Engineering Technologies at www.nicet.org or (888) 476-4238. Or, contact the International Communications Industries Association at www.ICIA.org or (800) 659-7469. MICHELSON is publisher and editor of the Cabling Standards UPDATE, a quarterly report dedicated to standards revisions focusing on cabling. She can be reached at (800) 492-8422 or by fax at (925) 846-9901. Her Web site address is www.cabingstandards.com.

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