Bosch PRAESENSA – The IP-based public address and voice alarm system with audio intelligence



Bosch set the bar high for quality, security, and reliability in Public Address (PA) and Voice Alarm (VA) systems since it’s launch of PRAESENSA in 2019. The Bosch PRAESENSA Ambient noise sensor is primarily significant in airports, campuses, factories, shopping malls and more.

The hum of equipment, the passing roar of vehicles or the loud buzz of a crowd can disturb the accuracy of voice messages. Likewise, messages or music can cause discomfort when they are played excessively loud in a quiet building. Automatic Volume Control technology assists when dealing with ambient noise changes. AVC – also referred to as Noise Dependent Volume Control, adjusts the loudspeaker volume according to the ambient noise levels and significantly solves the dilemma of a system being excessively loud in a quiet environment or too soft in a noisy environment.

Characteristics of PRAESENSA

The PRAESENSA Ambient noise sensor detects the ambient noise level and informs the system controller about changes. Announcements are automatically adjusted to an appropriate level above the ambient noise to ensure accuracy, whilst the background music is adjusted to maintain the perfect atmosphere. A maximum of four sensors can concurrently operate to cover a large area. In the event of a disconnection or failure of the device, the announcement volume will automatically set to its maximum within the applicable control range. This default setting ensures that the system will not interpret a missing sensor as a silent ambient level, resulting in decreasing the announcement level in error. The accuracy of messages and the system remains secure.

The adaptation threshold, slope, range, and speed of the Automatic Volume Control can be optimally configured for a specific application or location to ensure discreet effectiveness. Additionally, its behavior differs for short announcements in comparison to ongoing background music. The ‘sample-and-hold’ feature is commonly used for playback of prerecorded messages or for live speech calls. The noise level is sampled, and the latest level information is held and used during the call, which is not affected by the sound of the call itself or its associated echoes and reverberation. The tracking mode is used for background music – the ambient noise level is tracked, allowing continuous adjustment of the background music’s volume to suit the environment.

How Does It Work?

The sensor is directly connected to an IP network – one CAT5e cable can accommodate power over Ethernet (PoE) and data exchange. The device transmits ambient noise level data directly to the PRAESENSA system controller, which fine tunes the output level of the involved amplifier channels accordingly. Due to strictly level information being exchanged and no audio data, the occupied network bandwidth for this function is reduced and there is no risk of audio eavesdropping.

A back box is included to conveniently mount on walls or solid ceilings. The sensor can be flush mounted in hollow walls or suspended ceilings without using the backbox. The device is also water resistant (IP45) with or without the back box and is suitable for indoor and outdoor applications and comes with a black and white front cover for inconspicuous installation.

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