System Setup

Option 1:
Standalone System

The audio data is transmitted directly to the AKUT analysis servers via the network. At the microphone, the audio signal is digitized and transmitted via an optical fiber or a wired network.

Option 2:
Video camera with Audio Encoder

If other devices with an integrated audio encoder are already available, these devices (e.g. video cameras) can also be used to digitize the audio signals. Choosing this option can save money.

The microphones can be connected to the video cameras directly and the encoding of the audio signals is done by the video cameras. The video cameras send the IP audio data stream to the AKUT analysis servers.


The microphone is usually installed on the wall at a height of 3-4 meters. Wall mounting makes it easier to carry out any maintenance work later. Depending on the profile of the tunnel, the microphone can also be mounted on the ceiling.

A rapid commissioning of the system as well as an extensive acceptance test guarantees the full functionality of the entire system - starting with the microphone in the tunnel to the rapid alarming and activation of the correct camera image in the control center.


Microphones are normally sensitive to environmental conditions such as temperature, humidity and air pollution. Conventional microphones can’t be used in tunnel environments because they are not protected from humidity and dust, nor can they withstand the high-pressure water jets used to wash the sidewalls and ceiling. Special microphones were developed that are able to withstand these conditions. The microphones were subjected to comprehensive splashing water and ageing tests, the results of which were validated by acoustic measurements. 

More than 1800 of our special microphones have been in 24/7 use in tunnels since 2010 and have proven their robustness and sensitivity for detecting abnormal sounds.

The tunnel microphones are mounted on the connection box using a specially designed clamping device. Hydrophobic dust-proof membranes provide additional protection against ingress of water and dust. Despite these protective characteristics, the membrane is acoustically transparent across the entire frequency range. The membranes are fitted in protective caps and can be easily replaced during periodic maintenance.

AKUT® Voice-Scan

The voice scan is a powerful tool in AKUT for the detection of people in tunnels. In the case of a tunnel fire or smoke, even when cameras are already blind, the microphones can detect any kind of speech, screams and voices. The voice scan is activated in the case of a critical event by the operator. In this case, all microphones in the tunnel simultaneously scan for speech, voices or shouting people within the signals. In the traffic management system, the operator receives an overview of the entire tunnel and each person detected in the tunnel is shown on the display. This gives the operator an immediate overview of the exact locations of people in the tunnel. Based on this information the operator can direct the rescue teams to the exact position of the people.

The overview display is continuously updated so that the operator can also see where people are moving in the tunnel even with smoke and poor visibility in the tunnel.

Signal Health Monitoring

An AI-based software module for signal health monitoring is integrated to monitor permanently all microphones for the following faults:

  • Signal source malfunction
  • Low signal level
  • Clipping
  • Spectral quality degradation due to aging
  • Frame dropouts

Permanent signal errors due to malfunctions in the network or the signal transmission system are reported to the engineering management to trigger a rapid repair of the error.

Interface to Traffic Management System

The AKUT-system can be connected to any traffic management system (SCADA-system). Currently mainly OPC-UA and IEC 60870-5-104 are used as interface protocols.

AKUT can also be used as a standalone system and it is up to the tunnel operator how the integration of AKUT  into the traffic management system shall be carried out.

Do you want to ...


  • have more information about AKUT®

  • implement the system in the tunnel

  • learn about advantages and disadvantages

  • visit one of the equipped tunnels

  • collaborate and plan joint projects with AKUT®

  • praise us

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