REMEMBER THOSE NUTONE intercom systems that started cropping up in homes built in the late 1950s and into the early 1960s? They seemed so utilitarian; you could call the kids for dinner, summons someone to the phone, and in the higher-end systems, you could even pipe music from the radio into multiple rooms. Problem was, however, that it sounded like a dentist's office, so people turned the volume down or off, rendering the intercom function useless. In all the homes I visited in those days that were so equipped, the intercom system pretty much lay fallow, unused, except for an occasional impromptu performance of “Swanee River” done in the voice of Donald Duck by my waggish friend Scott. I wish I had a recording.

How far things have come. Today, one of the hottest digital features of new production homes is the whole-house audio system. According to John Sexton, director of new business development for Russound and the steward of the company's Builder Program, whole-house audio systems, more properly referred to as distributed audio systems, were included in 12 percent of all new homes built last year. And he cites statistics from the Consumer Electronics Association that indicate sales are growing at some 20 percent a year, which means that 14 percent to 15 percent of new homes will feature these systems this year.

One of the reasons for their popularity is that they sound good; the puny speaker in the intercom box has been replaced with high-quality loudspeakers usually installed in walls or ceilings. Moreover, advances through time have resolved problems associated with multi-room, multi-speaker analog systems. Digital technology eliminates issues like signal degradation the further the speaker was down the line, and it lessens heat created and power consumed by the amplifiers needed in those bygone days. A more important reason, however, is that the digitization of audio files has allowed easy portability from a central source, whether a computer, satellite, cable receiver, or even an iPod, to many places in the home.

DOWN TO THE WIRE Distributed audio systems come in several flavors and price ranges. According to Steve Dube, the inside sales manager for Newmarket, N.H.-based Russound, the production builders with whom Russound dealers work are most interested in relatively simple, low-cost systems that can be easily installed in a home wired with structured cable. He considers the wire to be essential: “You want the home to be ready for the future,” he says. And he notes that wiring distributed audio systems after construction can be considerably more expensive than installing them on an existing network.

PUMP UP THE VOLUME: Users control the audio system through a keypad, which, depending on the system's level of sophistication, can do anything from adjust the volume to change the source of the audio file to identify the file and the source on its touchscreen.

Most systems on the market today use the Category 5 (CAT 5) cable in the structured cable bundle to move audio from place to place. Dube (pronounced Doobee) explains that while the speakers used in most installations are still wired with traditional insulated copper wire, the pathway from the source to the keypad that controls the audio in each room is all digital, so it travels digitally. CAT 5 is best known for its use as the wire with which one connects a computer to a network. Distributed audio works in much the same way as a computer network.

The digital audio file is moved across the CAT 5 to the keypad, which contains an amplifier and is connected to the speakers in a particular room. It can control volume, and in all but the most rudimentary systems, it can control the source of the audio file and identify the file and the source on its touchscreen.

Mike Detmer, vice president of sales and marketing for Miami-based Niles Audio, says systems can range from a network of rotary volume controls hooked to a central source and amplifier, “a simple deal,” as he explains it, up to highly sophisticated setups that can play different sources in different rooms.

SOUND SPECTRUM The entry level is referred to as single-source, multi-room systems in which a radio or cable receiver or even an iPod, for example, is connected to several different rooms. In these systems, only one program can be played at a time, and that program is the same in all rooms. These systems, Detmer says, can run from several hundred dollars to the low thousands, with a typical installation with good quality speakers and a rotary control running about $350 a room. Installations using keypads will run slightly more.

The next level is called multi-room/multi-source, and these systems allow connection to any number of devices, including radio receivers, cable and satellite boxes, computers, CD players, and even sophisticated media servers. These will run in the low thousands for a typical installation, and they allow a homeowner to switch to and listen to a particular source from each room. But again, only one program (song or audio file) will be accessible in all rooms at a given time. These systems require an A-bus network with keypads, which allow for communication with various sources, even through a remote control.

Top-of-the-line systems are multi-source, multi-room, and multi-zone, and they are called integrated systems. In these, which can cost far more than $10,000 for a typical installation, a homeowner can access any of the sources that are hooked to the system and access any particular program. At the same time, someone in another room can listen to a different program from a different source, either through a keypad or with a remote control. In these systems, each family member can create personal databases of their own audio files and access them, as well as others, from any keypad in the home.