Guide specification: hearing loop and assistive listening systems

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Part 1: General

Place under Section 27 41 00, Audio-Video Systems, or the section your project uses.

1.1 Summary

1. Provide an audio-frequency induction loop (hearing loop) system for [list rooms and areas], complete with design, equipment, installation, commissioning, training and closeout documents.
2. [Optional] Provide a Bluetooth® LE Audio broadcast (Auracast™ broadcast audio) system for [list areas].
3. Provide loan receivers, neckloops and signage as specified.

1.2 References

1. IEC 60118-4:2014 with Amendment 1:2017, induction loop systems for assisted hearing: system performance.
2. IEC 62489-1, audio-frequency induction loop systems: methods of measuring and specifying the performance of system components.
3. IEC 63087:2026, assistive listening systems (for reference).
4. 2010 ADA Standards for Accessible Design, §216.10, §219 and §706, where they apply to the project.
5. ICC A117.1, the edition adopted by the authority having jurisdiction.
6. NFPA 70, National Electrical Code, including the support of cables above ceilings.

1.3 Definitions

1. Listening height: the height at which performance is designed and measured: [1.2 m (4 ft) seated] [1.7 m (5.5 ft) standing].
2. Useful listening area: the seating and standing areas to be served, shown on the drawings, excluding a band 0.6 m (2 ft) wide inside the loop conductor unless seats fall within it.
3. Spill: loop signal measured outside the area it serves.

1.4 Performance requirements

1. Field strength: at 1 kHz, the average across the useful listening area at the listening height shall be 400 mA/m (0 dB), and every measured position shall be within ±3 dB of it. Any position outside ±3 dB shall be listed in the commissioning report by location and reading.
2. Coverage: [every seat] [the areas shown]. Where the owner relies on §219.3 Exception 2 of the 2010 ADA Standards, every seat shall measure within ±3 dB.
3. Frequency response: 100 Hz to 5 kHz within ±3 dB of the 1 kHz level at representative positions.
4. Background magnetic noise, system off: no worse than −32 dB(A) re 400 mA/m, measured across the useful listening area before the design is finalized; −47 dB(A) or quieter is recommended by IEC 60118-4. Report sources found.
5. [Optional] Spill: no more than [−32] dB re 400 mA/m at [name each boundary: adjoining courtroom, room above, stage].
6. [Optional] Broadcast audio: at least one broadcast in a Standard Quality configuration (16 or 24 kHz) that hearing aids can join; planned signal of at least −70 dBm at the listening height with the room occupied; audio fed ahead of any loudspeaker delay; [private broadcast with a Broadcast Code] where privacy is required.
7. Receivers: the number required by Table 219.3 of the 2010 ADA Standards for the seating capacity, with at least 25% (not fewer than 2) hearing-aid compatible through neckloops, unless Exception 2 applies. [For venues outside the ADA rules: quantity per the owner.]

1.5 Submittals

1. Design: layout drawing with every conductor dimensioned; metal-loss assessment method and results by area at 100 Hz, 1 kHz and 5 kHz; predicted field map at the listening height, labeled as a model prediction; driver selection showing loop current and voltage headroom at 5 kHz.
2. Product data for drivers, transmitters, receivers, neckloops and signage.
3. The commissioning test procedure to be used, and a redacted sample report from a completed system.
4. Qualifications, per 1.6.

1.6 Quality assurance

1. Qualifications are judged on results: submit redacted commissioning reports from at least [three] completed loop systems measured against IEC 60118-4. Manufacturer training certificates may be submitted but are not a substitute for measured reports.
2. The person who measures the installed system shall sign the commissioning report. [Optional] Commissioning by an agent who did not design or install the system.

1.7 Coordination

1. Coordinate conductor installation with flooring, concrete pours and ceiling work; no covering before circuit tests.
2. Coordinate the assistive listening feed with the audio or DSP contractor, and power with the electrical contractor.

1.8 Warranty

1. [Owner to state workmanship warranty period and response requirements.]

Part 2: Products

2.1 Loop drivers

1. Current-drive amplifiers rated per IEC 62489-1, sized for the required loop current and voltage headroom at 5 kHz, including metal-loss correction.
2. Overlapping phased-array channels: drivers from the same product series.
3. Visible fault and signal indication.

2.2 Conductors and feeders

1. Loop conductors suited to the installation method: flat copper tape under floor coverings, round wire in ceilings, conduit or slabs.
2. Feeders: twisted or star-quad cable, one loop circuit per cable.

2.3 [Optional] Broadcast transmitters

1. Bluetooth qualified, capable of Standard Quality broadcast configurations, with [analog] [Dante] input and [encryption].

2.4 Receivers, neckloops and signage

1. Receivers meeting §706.2 to §706.6 of the 2010 ADA Standards, with charging station.
2. Signage with the International Symbol of Access for Hearing Loss; with a “T” where an induction loop is installed.

Part 3: Execution

3.1 Examination

1. Before finalizing the design, measure background magnetic noise and metal loss on site, and report the results.

3.2 Installation

1. Install per the approved design. Test every circuit with a driver before it is covered or sealed.
2. Support ceiling conductors independently of ceiling-grid hanger wires.
3. Feed: a dedicated assistive listening output carrying every program source, taken ahead of the room volume control and any loudspeaker delay.

3.3 Commissioning

1. Generate the 1 kHz reference with a separate signal source at the driver input; measure with a field-strength meter in the room.
2. Measure on a grid across the useful listening area at the listening height; set the level so the average reads 0 dB.
3. Measure frequency response at 100 Hz, 1 kHz and 5 kHz; set metal-loss correction where needed.
4. Measure background noise with the system off, and spill at each named boundary.
5. Phased arrays: test each channel alone, then together.
6. Listen through a loop receiver to the actual microphones.
7. [Optional] Broadcast: read the transmitter’s on-air settings; walk-test at numbered positions with a phone, a hearing aid and a loan receiver; record joins, dropouts, delay and audio quality.

3.4 Closeout

1. Commissioning report: instrument and serial number, date, every reading with its position, every position outside the window, settings, and the signature of the person who measured.
2. As-built drawings, driver and audio settings, receiver inventory against the required count, sign photos.
3. Staff training and a one-page operating guide at the sound position.

This guide specification is general information to adapt, not legal advice or a complete project document. Have your design professional and code official review the final specification.