S4T SAFETY FOR TUNNEL
ADVANCED EVACUATION SOUND SYSTEM WITH TUNNEL SPEAKERS
Public Address Systems utilised in tunnel applications need to deliver high level of reliability and at the same time be able to provide fair speech intelligibility in an acoustically challenging tunnel acoustic environment.
To ensure highest level of reliability EN54 compliant Voice Alarm Systems, fitted with multiple built-in redundancies and self-monitoring features, can be deployed in this scenario. An important aspect not to forget is the need to provide synchronization of the tunnel loudspeakers, which requires the amplification system to be able to provide delays from first to last loudspeaker.
smartVES offers extensive in-built DSP functionality allowing to optimize the sound system performance, including loudspeaker EQ and long distance delay.
ABT-TNL100 directional high-power horn speakers used in combination with the smartVES shall allow the sound system to reproduce clear and intelligible speech, at levels well exceeding 100 dBA accross the entire tunnel floor, not just in close proximity of a loudspeaker. With an opening angle of just 22deg and front-to-back attenuation of 35dB, the ABT-TNL100 allows to maximise the level of direct sound energy within the audience plane.
The PAVA system shall be used to broadcast general safety, as well as emergency messages.
The main role the system is the implementation of essential evacuation procedures and communication of a threat occurrence. In normal conditions the system can be utilized to communicate general security messages related to traffic and passenger safety. Pre-recorded messages shall be triggered by SCADA, PSIM, and/or FIRE ALARM interface. There shall also be an option for ad hoc paging using an Operators PC workstations and remote paging microphones.
smartVES TOPOLOGY
The smartVES is a TCP/IP based system. Both audio and control data signals are transmitted between system nodes (such as paging microphone, emergency microphones and controllers) in the digital domain.
The system is designed to operate is a distributed architecture. The system audio network shall comprise a number of controllers connected together in a redudant fibre-optic network. Each controller shall manage and amplifiers stack, including a backup amplifier, which shall be automatically turned on in case of a functional amplifier failure.
The controller shall allows to manage a group of amplifiers, with their loudspeaker lines. Each loudspeaker line shall be constantly monitored for open-, short- circuit and earth fault. Potential issues with the system shall not go un-noticed. In an event of a fault such an event shall be reported to the managing system, as well as signalled on each paging microphone and controller touchscreen operational interface located in the units front pannel.
The system shall be of master-less architecture, so that each controller shall hold the full system message store and configuration. Even in stranded mode, each controller shall be able to make paging using the resources available to it.
smartVES provides a tool for advanced digital sound processing and real-time noise tracking.
The speech temporal transposition algorithm (STTA) naturally and evenly changes the rate and duration of messages transmitted in real time by zone microphones (DFMS, DMS, DMS-LCD).
- When a speech signal is detected, the system determines its rate by buffering the signal. Then, based on the value of the STI index measured during auto-calibration, the instantaneous value of the speech signal slowdown coefficient is determined. As a result, the STTA algorithm obtains a natural speech sound, the tempo of which is adapted to the acoustic conditions in the broadcasting area.
The adaptive filtering algorithm allows the smartVES system to adjust the system’s frequency response in real time, which reduces the negative impact of noise on speech intelligibility. Many PAVA systems feature noise tracking, allowing you to automatically adjust the sound pressure level in a given zone based on noise sensor readings. This helps maintain an appropriate signal-to-noise ratio (SNR). However, it is worth noting that in this process the PAVA system usually attenuates the entire frequency band, which can lead to:
- Excessive energy consumption
- Increased sound reflections
- Constantly increasing the output level
- Decreased speech perception
Adaptive Filtration (AF) can change the frequency response of a system solely based on the impulse response of the noise level and the live noise spectrum. It is worth remembering that the frequency of noise affects how we hear other sounds. Noise at a specific frequency can make it difficult to hear sounds at the same or higher frequency. To counteract this, our solution does not reduce all frequencies, but applies filters to maintain a balanced signal-to-noise ratio in specific frequency ranges.