Induktive Höranlagen beim Freistaat Bayern: Planungsrichtlinien, Stand 01.01.2019 (Hearing loops in Bavarian state buildings: planning guidelines)

Summary

A German state's planning rules for hearing loops in public buildings: how metal and stacked rooms limit them, which layouts to use, how to check quality and keep them working, and how they compare with FM and infrared.

Key findings

• Says eddy currents in reinforced concrete and other metal can attenuate the loop signal by up to 10 dB per octave towards high frequencies; in its simulation of a 14 x 10 m perimeter loop, field variation across the room was 2.4 dB with no metal (7.5 A) and 13 dB over typical reinforced concrete (13 A), which it says fails IEC 60118-4 and calls for a phased array.
• Limits a perimeter loop to about 12 m wide without metal, and warns that makers' coverage figures assume no metal and ideal proportions: an amplifier rated for 1,000 m² may cover only about 80 m² to the standard in a real room. It says 100 V constant-voltage amplifiers almost never meet the standard because they cut high frequencies, and rules out comb or herringbone layouts for their dead zones.
• Says vertical spill between floors can hardly be controlled with reasonable effort, and that simulations are reliable only if the floor build-up can be measured in the shell, after the room layout is fixed; looped rooms should not be planned one above another, or a different system may be needed. In a few cases, spill travelled vertically through metal building parts, mainly columns, in ways not yet explained.
• Lists avoidable errors in loops already built: looped rooms directly above one another, neighbouring rooms with simple perimeter loops (which then cannot be used at the same time), and loops in classrooms, for which it points to FM systems instead.
• Requires a metal loss and interference field measurement before design, a test report to IEC 60118-4 with at least six evenly spread points, checks of loop cable continuity after laying, after the floor covering and at commissioning, and the loop's position recorded in the building plans.
• Requires loops to be on whenever the public is present rather than switched on by request, and to be checked at regular intervals and before use by a trained person with a portable loop receiver showing field level; it names transformers, distribution boards, faulty electrical installations and unsuitable dimmers as sources of interfering fields.
• Its comparison table rates equipment and installation cost as lowest for loops (factor 1), about twice that for FM and about 2.5 times for infrared, with no receivers to issue for telecoil users; it notes that ear-hook receivers are useless for hearing aid users, who need neckloops.
• The equipment-and-installation cost row is on printed page 23; the table's notes on page 24 credit permission from Carsten Ruhe of the Deutscher Schwerhörigenbund. The factors are presented without underlying project prices.
• Treats a loop's quality as proven only when every value the standard requires is reached and recorded at enough measuring points, and recommends a loop receiver with headphones so that staff with normal hearing can check the whole chain.
• In the summary notes added for this edition, it reports the closing statement of the 4th international congress on hearing systems and accessibility ("Future Loops", Berlin, 6-7 October 2017): classic induction is considered sustainable and supported worldwide, and the urgently needed standards for future multichannel systems have not yet been written. It then states that new technologies such as 2.4 GHz, Bluetooth and WLAN systems still have great development potential compared with induction and are beset by unresolved problems: power consumption, a strongly limited number of users, excessive delay of the audio signal, unsatisfactory range and no uniform standards.
• Says figure-of-eight loops leave a band without reception over the centre line, with null lines between the loops, while phased arrays give very even coverage without null lines; in its simulation a low-spill array keeps the field to the room it serves, with no crosstalk sideways.
• Says that in extreme cases, under flat metal structures, loops cannot be used and another kind of system must be chosen, among those it describes (including FM and infrared).
• Section 1.1, printed page 4, generally calls for loops in assembly rooms, auditoria and lecture halls used for assembly, and foyers used for events. Partial coverage in facilities such as extensive sports venues is to be agreed with disability representatives.
• Printed page 5 calls for locally confined loops at service and information counters with closed glazing and intercoms. Noisy counters and rooms handling confidential matters need case-specific discussion with disability representatives, with privacy secured where necessary by other measures such as acoustic separation.

Limits

Planning guidance for Bavarian state buildings, not a study (its cost factors match the German hard-of-hearing association's table, which the association itself calls qualitative; see dsb-2013-warum-induktive-hoeranlagen): the metal loss example is a simulation, and the 1,000 m² to 80 m² example and cost factors are given without data. One of the authors represents a hearing-loss organisation that advocates loops, and the guidance calls loops the best technical aid. It cites DIN EN IEC 60118-4 and German building standards. Its list of problems with 2.4 GHz, Bluetooth and WLAN systems reflects its 2019 status and gives no sources or measurements. The date is the edition's stated status date (Stand 01.01.2019); the file was created in December 2018 and last modified in December 2019.

Read the original

mobilitaet.bayern.de/assets/stmi/min/181217-induktive-hoeranlagen.pdf

Link checked 13 October 2026. We link to the original and do not host copies.

Cited in

• Auracast, hearing loop, infrared, RF or Wi-Fi: which suits which room?Disputed
• How many receivers and neckloops does each code require, and how should a loan pool be run?Partly answered
• What commissioning tests and pass limits will the standards require?Open
• Will equipment bought today meet the standards that follow?Open
• How is an installed hearing loop checked against IEC 60118-4, and how often does it pass?Partly answered
• Where do hearing loops fall short: metal, spill, noise and upkeep?Partly answered
• Where does infrared assistive listening work, and where does it fall short?Partly answered
• What does each system cost to install and to run over its life?Open

Cite this source

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