Which meters and apps measure loops and Auracast, and how accurate are they?

Why it matters

A tool can show that a signal is present without checking every part of the listening experience. The Center for Hearing Access recommends routine loop listening checks, while IEC 60118-4 separately specifies magnetic-field measurements. For Auracast, Auri's manufacturer guide warns that high received signal strength can accompany poor reception because of interference. Formal loop testing is covered in loop verification, and standards and acceptance limits in commissioning tests; this question concerns the tools and the limits of their readings^1,2,3.

What the evidence shows

Loop meters measure several different quantities. Manufacturer Ampetronic's FSM has separate modes for field strength, frequency response and A-weighted magnetic background noise, plus headphone monitoring. Its field reference is 400 mA/m, and its frequency-response check compares 100 Hz and 5 kHz with 1 kHz. NTi Audio's manufacturer application note describes an audio analyser used with a calibrated loop receiver. These are magnetic measurements; the sensor and its orientation are part of the measurement path^4,5.

The specifications below are makers' statements about their own equipment, read on 13 October 2026. Calibration accuracy at one frequency, frequency-response flatness, gain stability and display resolution are different properties, so the figures do not provide an accuracy ranking^6,4,7.

Position and settings matter. Ampetronic's manual asks for representative points at the intended listening heights and for the pickup coil to match the hearing-device telecoil orientation. It measures only the field component along that axis. Univox likewise identifies the coil's location as particularly important for small counter and neck loops. The Univox low range applies A-weighting, and its RMS and peak programme modes have different time responses. Record the mode and position with the reading so that later checks can reproduce the setup^4,6.

A loop app can be a measuring instrument when its hardware is included. Ampetronic's Loopworks guide requires an R2 receiver containing a telecoil for measurements; the phone app alone is not the described measurement system. Its product page specifies iOS 15 or later and official Apple adapters for Lightning or USB-C connections. The guide distinguishes simple meter operation from account-dependent saved readings and guided tests, and asks for calibration against the device settings, including recalibration after changing the receiver⁷.

Calibration has a standards basis, but the full procedure is not publicly readable here. The public contents of IEC 60118-4's consolidated 2017 preview identify informative Annex G, “Calibration of field-strength meters”, and Figure G.1, a triple Helmholtz coil for meter calibration. The preview does not show the procedure, so it cannot establish its apparatus tolerances or a universal recalibration interval. Separately, Univox recommends annual recalibration and a check after dropping or damaging its meter. Ampetronic recommends initial FSM recalibration one year after shipment, with a longer interval possible if no adjustments are needed. These intervals are manufacturers' recommendations^2,6,4.

Listening checks test the actual programme path. The Center for Hearing Access recommends staff listening with a loop receiver and headphones weekly and during microphone checks before events. Ampetronic's manual finishes with the actual venue sources and a check for comfortable, undistorted sound; NTi's procedure also includes hearing-aid users. A receiver's audible output or basic level indication does not supply the full field-strength, frequency-response and noise record those instrument procedures describe^1,4,5.

Auracast receiver tools can survey coverage and reception. Manufacturers Listen Technologies and Ampetronic describe two tools in their Auri RX1, requiring firmware 1.4 or later. TX Survey reports signal strength and strong, fair or weak marks without joining a broadcast. Signal Quality works on a joined broadcast and shows RSSI (received signal strength), quality and a possible-interference indicator. For Signal Quality, the guide asks for 5 to 6 seconds to let readings settle and for headphone listening; TX Survey separately asks for a few seconds. It publishes neither a numerical accuracy tolerance nor the category thresholds, and its unsigned “better than 60dB” survey target lacks a reference level. That wording cannot be turned into a dependable acceptance threshold³.

Phone discovery apps provide a different level of evidence. Developer Savant Labs' AuraCast Explorer listing, updated 1 August 2026, claims broadcast scanning and displays for signal strength, distance, codec and encryption status. It gives no calibration procedure, accuracy tolerance or distance-error bound, and includes a demonstration mode without Bluetooth hardware. The listing supports those feature claims; it does not validate the readings as a venue acceptance test. The app was not tested for this question⁸.

Protocol analysers and sniffers inspect the broadcast transport. Manufacturer Ellisys lists LE Audio support in its Vanguard, Explorer and Tracker models, distinguishing Vanguard's tZERO capture feature from the other two. Its technical note explains that capturing broadcast isochronous streams requires parameters carried in periodic advertising and that capture setup can miss early packets. Ellisys claims its proprietary method avoids these blind periods; no independent capture-error measurements are given. A packet record also cannot by itself report reception at every listener: broadcast receivers send no acknowledgements, and Auri's manual says receiving-device sensitivity and obstructions affect range^9,10,11.

Audio measurements need their own controls. In Bluetooth SIG's member-funded standards work, LC3's post-filter, used at lower bitrates, can raise a full-scale sine signal by up to 0.5 dB; a 6,427 Hz tone usually keeps the gain difference below 0.03 dB at the specified 16, 24, 32 and 48 kHz sample rates. This concerns codec measurement, not total venue-system accuracy. In a manufacturer-authored bench report using Cloud2GND's broadcaster, HEAD acoustics provided access to test equipment. The output from one tested consumer receiver glitched about every 15 minutes; the author suspected the receiver, while leaving the test PC as another possible cause. The author notes that buffering can separate a fault from its audible effect by up to 60 ms and recommends automated capture for rare faults. The report supplies no representative sample of venue receivers^12,13.

Where sources disagree

The cited sources do not provide an independent comparison of meter accuracy. Ampetronic claims an accuracy lead for Loopworks, but its published flatness and gain-stability figures do not measure the same property as Univox's calibration tolerance at 1 kHz. Neither source provides a comparative error dataset^7,6.

The Auri commissioning guide says Signal Quality can be checked empty and in use, but also places an empty-venue instruction beside that test. Its system manual explicitly calls for validation under normal, fully occupied conditions. An empty-room survey and an occupied-room check therefore need to be distinguished in the test record; the guide's strong/fair/weak display is not evidence of equal reception by all hearing devices^3,11.

What would settle it

For loop meters, independent tests against a documented reference field across frequency and level, repeated with different units and supported phone/adaptor combinations, would test whether the makers' specifications hold in use. The complete Annex G procedure and an uncertainty budget would help interpret differences near a system's acceptance limit^2,6,7.

For Auracast, measurements comparing phone readings, receiver quality indicators, packet capture and actual audio output at the same positions would establish what each indicator predicts. Repeating them with different receivers, occupied rooms and long recordings would address receiver sensitivity, interference, packet concealment and intermittent faults identified by the cited sources^11,3,10,13,8.

Planning while it is open

• For loop measurements, select a tool and range that cover the required field, frequency response and noise checks; follow its specified test signals, filters, coil orientation and listening positions^4,6.
• Check calibration history, battery indications and any damage before relying on readings. Follow the maker's recalibration interval and, for Loopworks, its receiver/device calibration procedure^4,6,7.
• Keep routine listening checks with the venue's real microphones and programme sources alongside instrument results, including checks by hearing-aid users^1,5.
• For Auri surveys, allow readings to settle, record several locations, listen on headphones and compare empty and occupied conditions. Investigate poor quality even where RSSI is high, and account for receiving-device sensitivity^3,11.
• For deeper Auracast diagnosis, verify the analyser's specific LE Audio capture features and combine packet information with audio-output measurements. Allow sufficient test duration to capture intermittent faults^9,10,13.

Sources

1. Hearing Loops: Basic Troubleshooting. Center for Hearing Access (The John G. Shedd Institute). Center for Hearing Access, undated (read 13 October 2026). Nonprofit advocacy (Center for Hearing Access, an advocacy and education initiative of The John G. Shedd Institute for the Arts) ↩︎ https://centerforhearingaccess.org/hearing-loops-troubleshooting/
2. IEC 60118-4:2014 Electroacoustics - Hearing aids - Part 4: Induction-loop systems for hearing aid purposes - System performance requirements. IEC TC 29 (Electroacoustics). International Electrotechnical Commission, 11 December 2014. Standards body (International Electrotechnical Commission; the full text is sold, and only the abstract is public) ↩︎ https://webstore.iec.ch/en/publication/798
3. Auri user guide: RX1 commissioning tools (UP3B613-1). Listen Technologies and Ampetronic (Auri). Ampetronic, 2025. Manufacturer (Listen Technologies and Ampetronic) ↩︎ https://www.ampetronic.com/wp-content/uploads/UP3B613-01-Auri-User-Guide-RX1-Commissioning-Tool_A4_WEB.pdf
4. Field Strength Meter Handbook (UP14301-13). Ampetronic, undated (read 13 October 2026). Manufacturer (Ampetronic, maker of the FSM and hearing loop systems) ↩︎ https://www.ampetronic.com/wp-content/uploads/UP14301-13-HB-FSM-A5-format.pdf
5. Application Note: Induction Loop Systems with XL2 Analyzer (AFILS). Norman DI (for NTi Audio). NTi Audio, 12 January 2021. Manufacturer (NTi Audio, which sells the analyzer and signal generator the note is written for; the author, David Ian Norman, is described in the note as a member of the IEC committee for these systems) ↩︎ https://www.nti-audio.com/wp-content/uploads/NTi-Audio-AppNote-AFILS-with-XL2.pdf
6. Univox FSM: Digital Field Strength Meter for AFILS, User manual (UP_5-0142-1.0-EN). Bo Edin AB / Univox, undated (read 13 October 2026). Manufacturer (Bo Edin AB / Univox, maker of the meter and hearing loop systems) ↩︎ https://univox.eu/wp-content/uploads/sites/2/2023/11/UP_5-0142-1.0-EN.pdf
7. Loopworks Measure R2 field strength meter. Ampetronic, undated (read 13 October 2026). Manufacturer (Ampetronic, maker of Loopworks Measure and the R2 receiver) ↩︎ https://www.ampetronic.com/products/loopworks-measure-receiver-field-strength-meter-r2/
8. AuraCast Explorer: Google Play developer listing. Savant Labs. Google Play (developer listing by Savant Labs), 1 August 2026. Manufacturer (Savant Labs, developer of AuraCast Explorer) ↩︎ https://play.google.com/store/apps/details?id=com.savantlabs.auracastexplorer&hl=en
9. Ellisys Bluetooth analyzers comparison chart. Ellisys, undated (read 13 October 2026). Manufacturer (Ellisys, comparing its own Bluetooth analyser models) ↩︎ https://www.ellisys.com/products/btcompare.php
10. Capture and Security Challenges Relating to the LE Isochronous Physical Channel: The Benefits of tZERO Tracking Technology. Ellisys, September 2021. Manufacturer (Ellisys, maker of Bluetooth protocol analysers) ↩︎ https://www.ellisys.com/technology/een_bt10.pdf
11. Auri System Manual. Listen Technologies and Ampetronic. Listen Technologies (online documentation), 1 October 2026. Manufacturer (Listen Technologies and Ampetronic, makers of Auri) ↩︎ https://www.listentech.com/docs/auri-user-manual/
12. Performance characterization of the Low Complexity Communication Codec. Bluetooth SIG Generic Audio Working Group. Bluetooth SIG, 13 June 2023. Standards body (Bluetooth SIG, an industry association funded by its member companies, which owns the Auracast trademark; laboratory tests by SenseLab of FORCE Technology and by Fraunhofer IIS) ↩︎ https://www.bluetooth.com/wp-content/uploads/2023/07/LC3Characterization_WP.pdf
13. Evaluating and testing Bluetooth LE Audio performance: a guide for developers, part 3. LaMacchia B (Cloud2GND). audioXpress (print issue February 2026; online 21 April 2026), February 2026. Manufacturer (Cloud2GND, maker of the AW100 broadcaster used; HEAD acoustics provided access to test equipment and materials) ↩︎ https://audioxpress.com/article/evaluating-and-testing-bluetooth-le-audio-performance-a-guide-for-developers-part-3

Change log

• 13 October 2026Published with 13 sources.
• 13 October 2026Citation audit clarified calibration scope, receiver-tool settling times and bench-test limits; expanded supporting records.
• 13 October 2026Second citation check retained the instrument comparisons; consolidated the Auri record and its interference qualification.

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