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Installation Profile: Legislative Sound

Nov 1, 2007 12:00 PM, By Garret Maki and Rodrigo Ordoñez

Inside the U.S. Senate Chamber’s digital audio upgrade.

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Original 1994 Article

Chamber System Design Comes Full Circle

The recent digital audio upgrade in the Senate Chamber was required to provide the same quality and reliability as the system that had served the Senate for the last 13 years, but at the same time, it took advantage of newer digital audio distribution techniques and DSP technology to provide modern monitoring and control capability.

As documented in Sound & Video Contractor in late 1994, a computer-based audio system was permanently installed into the United States Senate Chamber for the first time.

That work was performed between July 1992 and January 1995 by Colorado's Peak Audio.

In September 2004, U.S. Senate officials awarded the modern version of that company, Cirrus Logic's Peak Audio consulting division, a contract to replace that audio system with a newer version that would provide the same level of quality and reliability while taking advantage of newer digital audio distribution techniques and DSP technology. (See sidebar for details on the original design.)

After breaking off from Cirrus Logic in 2005, K2 Audio became an independent audio consulting firm based in Boulder, Colo., but stayed on the ongoing project as the consultant in charge. General Communications (whose Government Services Division is located in Manassas, Va.) served as the contractor responsible for the installation of the upgrade to the audio technology within the historic chamber.

A peek inside the Senate Chamber. Photo Courtesy U.S. Senate Historical Office.

Because the Senate Chamber cannot be taken offline outside of scheduled Senate recesses, the installation had to be done in stages. Initially, systemwide testing was completed and presented to Senate officials at K2 Audio's office in Boulder. Most cabling was then installed during the summer congressional recess, with additional infrastructure work, including the replacement of most of the loudspeaker drivers in the Chamber's Gallery, completed during the following winter recess. New desk units, signal processing, and distribution equipment were installed during last year's summer recess, in time for the first use last September.

The audio system includes the functionality of an advanced delegate conference system, but it also includes support for advance monitoring, control, and processing. In addition to sound reinforcement, it provides the only audio feed allowed outside the Chamber, which is then used by radio and TV networks for broadcast distribution. Thanks to live coverage from C-SPAN any time the Senate is in session, the quality and correct operation of the system impacts millions of viewers each day.


The Chamber itself is a rectangular room that consists of two main areas: the Floor and the Gallery. The Gallery is a balcony that runs along all four walls and seats the audience, the press, and the audio system operator. In the lower center section of the Chamber is the Floor, where legislative sessions take place. On the Floor, a designated desk is provided for each senator. The desks are arranged in four semi-circular rows with each of the two major political parties grouped on either side of a center aisle.

Each senator, the legislative clerk, and the Senate's presiding officer are provided with individual, always-on microphones. Each one of these input locations has a local mechanism for muting the microphone when it is not in use. Remote control functionality is also provided. Sound reinforcement loudspeakers are distributed throughout the Chamber for high intelligibility and even coverage in every zone. Although the system is typically used for daily legislative sessions, periodic special events, such as the swearing in of new senators, require the provision of many in-room and external auxiliary inputs and outputs.

Desks move frequently due to elections, changes in preference, and many other events that may alter the Senate's structure. Therefore, the system needs to allow for rearrangement of each desk's inputs and outputs. With more than 200 cable drops where desks can be located, the system allows the control and audio mix settings to be reconfigured accordingly.

The United States Senate Recording Studio (SRS) is responsible for the production and distribution of all audio and video feeds originating in the Senate Chamber. At press time, the SRS was in the process of relocating its entire facility to the new Capitol Visitor Center (CVC) being built on the northeast side of the U.S. Capitol building. This move would have placed the Senate Chamber equipment racks beyond the cable-length limitations of the technology used in the previous sound system. Although the previous system was extremely reliable — with no failures during its entire life — the move presented an opportunity to upgrade the technology and replace an old system for which some replacement parts were no longer available.

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