Ambient noise sensor added to Bosch Praesensa system

Bosch has expanded its Praesensa Public Address and Voice Alarm (PA/VA) system with an ambient noise sensor.

The noise sensor monitors the ambient noise level and alerts the system controller about changes. Announcements are then automatically adjusted to a comfortable level above the ambient noise to ensure intelligibility, and background music is adjusted to maintain the right atmosphere.

Up to four sensors can operate together to cover a large area. In the event of a failure or disconnection of the device, the announcement volume is automatically set to its maximum within the applicable control range. This fail-safe is designed to ensure that the system does not interpret a missing sensor as a silent ambient level and decrease the announcement level mistakenly.

Adaption threshold, range slope and speed can by optimally configured according to application and location. Its behaviour is also different for short announcements compared to ongoing background music. Sample-and-hold mode is used for live speech calls and playback of pre-recorded messages. The noise level is sampled and the latest level information is held and used during the call; this is not affected by the sound of the call itself or its associated reverberation and echoes. Tracking mode is used for background music; the ambient noise level is tracked, allowing the continuous adjustment of the background music’s volume to suit the environment.

The sensor is directly connected to the IP network – one CAT5e cable can accommodate data exchange and power over Ethernet (PoE). The device communicates ambient noise level data directly to the Praesensa system controller, which adjusts the output level of the involved amplifier channels accordingly. Because only level information is exchanged and no audio data, the occupied network bandwidth for this function is minimised and there is no risk of audio eavesdropping.

A back box is included for mounting on solid ceilings and walls. Without the back box, the sensor can be flush mounted in hollow walls or suspended ceilings. The device is water resistant (IP54) with or without the back box and can be used indoors and outdoors. It comes with a black and white front cover.

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