Outdoor installation: UWB positioning ensures orientation in the district of the senses
by Matthias Fuchsarticle from the archives of
With a combination of UWB positioning from logistics applications and the Dante audio system, the world is made more tangible for blind and visually impaired people in Berlin. A tour through the “district of the senses”, which also serves as training courses.
The eye is undoubtedly our most important sensory organ. If its function is impaired, it means a fundamental change in almost all living conditions for those affected. The Blindenhilfswerk Berlin eV has been supporting blind and visually impaired people since 1886 with a wide range of residential, educational and leisure options and a high level of expertise. In the summer of 2023, the “District of the Senses” was opened on the club grounds in the Berlin district of Steglitz – an approximately 300 square meter garden area that brings the topic of visual impairment closer to the public. As a training area, it also offers basic training for blind and visually impaired people.
This is an approximately 150 meter long, walkable course with seven stations that acoustically and tactilely convey to the “user” everyday situations from the urban environment (road traffic, public transport, etc.). Carsten Zehe, managing director of the Blindenhilfswerk Berlin eV, explains the initial conditions: “How do you guide a non-sighted person safely and reliably through an unfamiliar environment? Usually through tactile guidance systems and acoustic signals – that’s basically nothing new. However, it becomes interesting and technically demanding when you want to convey very specific auditory content to a person in a certain position – without having to equip the person in question with special and possibly complex technology.
For this purpose, a concept for the contents of the installation was first developed in-house and technical solutions were considered. The Berlin company Detailklang was ultimately chosen to realize the project. Detailklang has many years of experience as a provider of media systems and sound reinforcement concepts of various designs.
Interlocutor Martin Hachmann from Detailklang, however, emphasizes the uniqueness of this project and the attractiveness of the challenges associated with it: The first priority here was the question of a suitable location system that reliably recognizes users on the site and thus makes it possible to use the loudspeaker closest to them to convey certain audio content – sounds or spoken texts.
Outdoor speakers: One of the 23 Sonance Landscape (Image: Matthias Fuchs)
A wide variety of concepts, including light barriers, WLAN, Bluetooth or other smartphone-based technologies, were rejected as too inaccurate, unreliable or too complicated to use. Ultimately, they decided on ultra-wideband (UWB) tracking from the Estonian manufacturer Eliko. It offers position accuracies of 10 to 50 centimeters, up to 100 position queries per second, low susceptibility to interference and the use of extremely large frequency ranges with a bandwidth of at least 500 MHz. The position itself is determined by determining the transit time between a moving object (“tag”) and at least three receivers (“anchors”). Such systems are usually used for complex logistics applications. Thanks to the highly specialized “misappropriation”, the project quickly attracted great interest from the manufacturer Eliko despite the comparatively low budget.
Eliko UWB-Tracking: The tracking system has six anchor points; Three of them are arranged staggered from each other at a height of around 4 meters on the long sides of the site and scan the entire site. (Image: Matthias Fuchs)
Orientation via audio: up to 32 streams in parallel
On the audio side, the weatherproof installation consists of 23 passive outdoor speakers of the Sonance Landscape Series type, which were mounted largely invisibly at certain points on the site. They are characterized by high audio quality. There is also a subwoofer and a structure-borne sound transducer, known in the district of the senses as a “bass plate”. The latter serves to convey a sound event in a tactile manner. Dante speakers were omitted. The large number of sound sources allows individual visitors to be addressed directly and traffic scenarios that appear very realistic to be created. Extensive sound coverage of the area should be deliberately avoided.
The speakers are powered by six Powersoft Mezzo DSP power amplifiers and a Quattrocanali 1204 DSP+D. This sound system is controlled by a Core 510i system processor with a Dante expansion card from QSC. It addresses each speaker via its own Dante channel and can be flexibly routed. A total of up to 32 audio streams can be played in parallel.
Traffic lights: Since original traffic lights were not available, Detailklang procured a traffic light system from a traffic training area supplier. (Image: Matthias Fuchs)
While the components listed so far are a combination of commercially available products, the interface between tracking and audio system is largely a new development by Martin Hachmann: It uses QSC’s Q-Sys programming environment and expands it with its own for this project Custom-made scripts created in the Lua scripting language. This software prepares the data from the tracking system so that the QSC Core 510i processor is able to select the appropriate audio signal at certain moments and route it to specific speakers. If necessary, a user equipped with a tag can trigger a specific sound event at any point on the site without latency.
Earthworks: During the construction phase, the entire site was completely redesigned and ducts were created for cabling; the cabling is maintenance-free. (Image: Matthias Fuchs)
The software currently offers several scenarios that can be accessed easily. With just a few clicks, the system can be switched from a school class visit to a training course for the visually impaired. A tablet serves as the system’s remote control and editing interface. Using script extensions, new scenarios can also be created as desired. This means that the system can be used flexibly in the long term despite the permanently installed hardware.
Control technology: The QSC Core 510i processor, the power amplifiers and the network technology are located in the boiler room of the neighboring building. The technology cabinet there, put together by Martin Hachmann, houses a remote-controlled power socket with a temperature sensor for controlling a fan at the top. Below is an AVLine switch from Netgear with preconfigured presets for AV applications such as Dante. This is followed by a patchbay for the cables in the outdoor area. Below is the server of the Eliko tracking system. It evaluates the system’s information and sends its data to the control LAN, which also contains the QSC Core 510i processor. Invisible behind one of the ventilation grilles is a music streaming system that can be controlled via smartphone. You can see the Sennheiser wireless in the middle. Below are the six 324AD Dante power amplifiers from Mezzo, each with an output of 4 × 80 watts. Thanks to power sharing, the overall performance can be used very effectively. The large power amplifier below drives the subwoofer and the bass plate. At the bottom there is a relay circuit designed by Martin Hachmann to control the traffic lights. Here the connection to the QSC Core takes place via a general purpose interface. (Image: Matthias Fuchs)
In addition, the software must ensure that audio files are not accidentally played multiple times or left out, or interrupt each other, or the like, even when there is a maximum density of people on the site. If necessary, the “presenter” can actively intervene in the processes via a tablet and, for example, trigger audio files manually. It is also possible to address visitors using a Sennheiser wireless microphone.
Two views of the control software: It offers functions for easily selecting presets (“programs”) for different scenarios as well as real-time intervention options in their process. In addition, several playback parameters can be influenced. (Image: Matthias Fuchs)
In addition to the Blindenhilfswerk Berlin and Detailklang, a local horticultural company was also entrusted with the realization of the project. First, the site and the subsoil were prepared and trenches were created for laying cables. According to Martin Lachmann, the decision was made to use high-quality outdoor cables and PVC pipes protected by a gel coating. Thanks to the flexible software solution, the system is designed to be sufficiently variable in the long term. In addition, all connection points between cables and devices are easily accessible at all times.
Overview: Arrangement of all installation components (Image: Matthias Fuchs)
The audio files to be played in the installation, essentially traffic noises and linguistic content, were created by the Berlin sound designer Patrick Zahn together with the Blindenhilfswerk Berlin eV. Numerous blind and visually impaired people living on the club premises were also involved in the voice recordings. A player serves as an additional audio source, which allows the installation to be used as a sound system if necessary – for example for events organized by the aid organization for the blind.
The implementation, including planning and construction breaks, took around one and a half years. A not insignificant proportion went to the development of the tracking/audio interface including the user interface.
Project team: Carsten Zehe and Elfi Schwab from the Blindenhilfswerk Berlin eV with Martin Hachmann, detailed sound (from left) (Image: Matthias Fuchs)
The entire network is divided into four VLANs – one each for the tracking system, for Dante, for the control and another for maintenance purposes. The power supply to the outdoor devices is via PoE. In addition to the LAN cables, no other cabling is necessary. Any expansions, such as the Dante system, do not require any additional power supplies – this is particularly practical in outdoor areas.
