Case Study | Biamp Systems - Lisbon Underground | Tech Electronics
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Biamp Systems - Lisbon Underground

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In preparation for the Euro 2004 football championship, the city of Lisbon commissioned a major upgrade for its underground train network. The project required a completely revamped audio paging and emergency notification system in 11 new tube stops, as well as transitioning the 40 stations already on the network. The system needed to interact with the existing audio PA system while not holding back performance in the newer stations.


Audium designed the upgraded system around an array of Biamp's® AudiaFLEX DSP units, chosen for their ability to manage the new system while integrating seamlessly with the older equipment. Since each AudiaFLEX system operates as a single network over CobraNet™, installation requires fewer materials and resources. This design provides enhanced paging and excellent sound, along with a high degree of failure tolerance and self-diagnostics, meeting the need for an emergency evacuation system as well as day-to-day use. Thanks to networked central control, the system can easily be expanded for future stations.


The central core of the system design consists of twin AudiaFLEX networks, performing matching functions in parallel, one primary and one redundant. Signals are then broadcast into the network on different CobraNet bundles and each station receives both bundles, automatically switching to the redundant bundle in case of failure of the primary bundle.

Organized for various levels of routing of pre-recorded and live messaging, the remote operating system is optimized to page to all stations, to all stations on each of the four train lines, to a single station, or to one zone within one station. It also handles local live paging calls at each station, permanent transmission of background music and — as part of a stepped-up security strategy — audio monitoring of any selected station zone.

The local system for each of the 11 new stations consists of a CobraNet-enabled Biamp AudiaFLEX with four analog inputs and outputs, a Biamp Audia® Logic Box, and a Crest Audio Cki 500 amplifier with Ethernet module. Audio monitoring of the amplifier output is done via a TCP/IP connection, breaking down each protocol suite into layers of general functionality for the entire system. The AudiaFLEX executes all the routing and audio processing, including a complex ambient noise compensator [ANC] system, used to overcome the high-level sound variations on station train platforms. The ANC system delivers fine frequency and volume control for small zones, offering an effective way of addressing acoustic problems at nominal cost.

At each of the 40 existing stations, an AudiaFLEX was installed on the existing rack, replacing all previous routing and audio processing equipment. All the new equipment was connected to the Metro's existing Ethernet network using fiber-optic cable, helping to reduce costs and increasing signal carrying capacity. Inside the system's central control station, Metro staff has access to all system functions, as well as pre-recording and playback of messages, thanks to custom software featuring a GUI (graphical user interface) developed specifically for the project by Audium.

Audia software loaded on a portable PC controls system maintenance, allowing remote access to every station, not only for fault diagnosis but also for adjustments to the background level, the page level, the zone level and equalization.


Along with the noisy station environment, the topology of the Lisbon Underground network imposes additional demands on the system. Audium's choice of Biamp AudiaFLEX equipment provides multi-tasking efficiency, improved user controls and cost-saving resource utilization, as well unlimited networking potential. Audia's reliability and flexibility enhance both station communications and security.