Summary
A field test of Auracast, FM and 5G internet streaming at an outdoor event of about 2,000 people on Helvetiaplatz, Zurich, on 2 May 2026.
Key findings
- The transmitter stood about 2 m high beside the left main loudspeaker, in an open area of about 30 x 20 m surrounded by buildings at some distance.
- With the authors' hearing aids and receivers, reception was reliable for virtually all receivers only up to about 5 m in front of the transmitter. At about 8 m, with the tester's own body between a chest-worn receiver and the transmitter, there was no reception.
- Outdoors the signal relied almost entirely on line of sight; one person in front could disrupt a belt- or chest-worn receiver, and without line of sight reception was "practically always unacceptable". The authors suspect the many phones and other Bluetooth devices in the crowd added packet loss.
- A functional test in the empty square did not reveal these limits; only the crowd did.
- Measured latency: Auracast 43 ms to a receiver and 54 ms to a hearing aid; FM 8 ms; 5G streaming about 360 ms. Sound from the loudspeakers took 25 to 100 ms to reach listeners, depending on position, so the authors also give each system's difference from that airborne sound: FM 17 to 92 ms, Auracast 18 to 57 ms (receiver) and 29 to 46 ms (hearing aid), and streaming 260 to 335 ms.
- The authors recommend a difference of at most 40 ms between airborne sound and the hearing system. At this event Auracast came closest to that value, FM sometimes exceeded it depending on position, and streaming fell far short; no system kept the two in step across the whole square, and the authors suggest offering channels with different delays for the front and back.
- The FM system, used because it was already in place, gave stable transmission with very low latency, but neckloop (telecoil) users heard interference from the magnetic fields of nearby tram overhead lines. The authors note that keeping existing FM systems can avoid buying Auracast receivers with neckloops, and that transformer stations, high-voltage lines and trains or trams can disrupt telecoil reception.
- The authors conclude that Auracast did not reach the often-promised 100 m and should for now be treated with caution, as a supplementary option outdoors. The 5G streaming gave uninterrupted reception across the venue but with high latency.
- Notes that manufacturers often advertise ranges of over 100 metres under ideal conditions.
- On PDF pp. 2-3, the empty-space check showed no difference between receivers worn on the belt, chest or ears (hearing aids and headphones); the report gives no date or measured distance for this check.
- PDF p. 4 identifies the internet service as Accessify over 5G. Under Limitations in the device connection, the authors report occasional interruptions on the Bluetooth link from phone to hearing aid, especially with the phone in a back pocket and the body blocking the path. This problem was not observed with in-ear headphones. The venue-wide internet reception statement does not establish uninterrupted delivery through every hearing aid.
- The table on p. 4 separates measured system latencies from differences to airborne sound. Its footnote derives the differences from 25-100 ms sound travel time at front/back positions. The Auracast entries (18-57 ms and 29-46 ms) are those endpoint differences, not bounds on the absolute offset at every intermediate position; at the front the stream is later, and at the back it is earlier. FM is earlier at both endpoints and Accessify later at both.
- On page 4, the streaming comparison reports interruptions between a smartphone and hearing aids over Bluetooth, especially with the phone in a back pocket blocking the path; this did not occur with the in-ear headphones tested. The uninterrupted coverage refers to the internet feed, not every complete listening path.
- The practical recommendation on page 5 asks organisers to test outdoor systems in advance and consult a specialist.
Limits
One event, one transmitter position and the authors' own receivers; machine-translated from German.
Read the original
Cited in
- Should the Auracast stream be delayed to line up with the loudspeakers?Open
- How far does one transmitter really reach in a full room?Partly answered
- Auracast, hearing loop, infrared, RF or Wi-Fi: which suits which room?Disputed
- How much do crowds, phones and Wi-Fi reduce reliability?Open
- Can Auracast serve outdoor events?Not reliable yet
- Which radio bands can venue FM and RF systems use, and what limits them?Partly answered
- What works for announcements and ticket counters on buses, trains, stations and airports?Partly answered
- Do neckloops give telecoil users good sound from FM, infrared, Wi-Fi and Auracast receivers?Not reliable yet
Cite this source
Pro Audito Schweiz. Auracast practical test outdoors. Pro Audito Schweiz; English reprint by the Center for Hearing Access. 16 September 2026. https://centerforhearingaccess.org/wp-content/uploads/Pro-Audito-Schweiz-Auracast-practical-test-outdoors.pdf (accessed 13 October 2026).
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