The loud buzz of a crowd, the passing roar of vehicles or the hum of equipment can affect the intelligibility of voice messages. Similarly, music or messages can cause discomfort, when they are played too loudly in a quieter building.
Automatic Volume Control (AVC) technology helps to deal with these ambient noise changes. The PRAESENSA ambient noise sensor from Bosch changes the loudspeaker volume, according to the ambient noise levels and automatically solves the dilemma of a system being too loud in a quiet environment versus too soft in a noisy environment.
The PRAESENSA ambient 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, in order 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 ensures that the system will never interpret a missing sensor as a silent ambient level and decrease the announcement level mistakenly. The intelligibility of messages is ensured and the system remains safe.
The sensor is directly connected to the IP network – just 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 minimized and there is no risk of audio eavesdropping.
For Automatic Volume Control (AVC) actions to be discreet yet effective, its adaptation threshold, range, slope and speed can be optimally configured for a specific application and location. Furthermore, its behaviour is different for short announcements, when compared to ongoing background music. Sample-and-hold mode is used for live speech calls and playback of prerecorded 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 PRAESENSA ambient noise sensor can be used indoors or outdoors, and installed as a flush-mounted or surface-mounted solution. This makes it a good fit for applications, such as campuses, shopping malls, airports, railway terminals, and factories.
