Assistive Listening Knowledge Base

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How far does one transmitter really reach in a full room?

From https://assistivelisteningknowledgebase.org/questions/real-range/ · updated 13 October 2026

  • Affects venues, installers, specifiers
  • 19 sources
  • Updated
  • First published

Technologies: Auracast

In brief

Several makers and the Bluetooth SIG cite about 100 m or more; one maker states 30 to 40 m. Independent results range from every seat of an empty 22 x 80 m hall, from one transmitter near the middle, to only about 5 m for reliable reception across virtually all tested receivers in an outdoor crowd, and expert guidance puts real range at about 20 to 30 m.

Why it matters

Auri’s manufacturers advise adjusting transmitter mounting arrangements to suit the venue1. An estimate based on advertised range can leave the back rows, or a full room, without usable sound2,3.

What the evidence shows

  • About 20 to 30 m in practice. A standards-committee expert reports a real range of about 30 m rather than the advertised 100 m, and recommends keeping the farthest seat within 20 to 30 m2. Pro Audito estimates that the roughly 100 m data-sheet range of 20 dBm transmitters could fall to 20 to 30 m under extreme conditions4.
  • A full room is the hard case. The same expert notes that a fully occupied room with heavy Wi-Fi can shorten the reliable distance considerably2. The Bluetooth SIG recommends repeating the walk test with the room occupied5.
  • Large hall test. Pro Audito's independent test used products lent free by manufacturers in a 75 x 57 m hall with an 18 m ceiling, placing each transmitter for maximum distance. Of the 51 transmitter-receiver pairs included in the overall evaluation, 26 had dropouts and distortion from about 5 to 10 m and heavy dropouts or distortion from about mid-hall, while 16 pairs received throughout the hall with at most occasional dropouts or low-level audio artefacts6.
  • Empty theatre test. In an empty hall of about 22 x 80 m, one ceiling-mounted transmitter near the middle was received at all seats; reception with a full audience was not tested7.
  • Outdoors in a crowd. With a transmitter at about 2 m and about 2,000 people, reception was reliable across virtually all tested receivers only within about 5 m; a listener's own body blocking the line of sight at 8 m stopped reception3.
  • The receiver matters as much as the transmitter. In the hall test, one transmitter rated flawless with one receiver and worst with another6.
  • SIG statements give no conditions. A SIG handout gives about 100 m for an Auracast broadcast from a mains-powered public transmitter, against about 10 m for paired Bluetooth audio, without test conditions8. A SIG paper states that in most cases one transmitter will cover a whole venue, citing a demonstration across all 1,085 seats of Alice Tully Hall without method or measurements9.
  • Makers' figures differ widely and give no method. Stated ranges are 150 m in open range for one transmitter, up to 100 m in open space with the maker's own receiver for another, and 30 to 40 m to -70 dBm on its own receiver for a third10,11,1. A hearing-aid maker reports reception at up to 211 m in its own unpublished testing12.
  • Power is limited by regulation. In Europe the harmonised standard gives the limits used to show conformity13. The SIG's regulatory guide explains that a device at +10 dBm EIRP or more must meet the standard's adaptivity requirements or accept limits on how much of the time it transmits, and names staying below +10 dBm as the simplest way to avoid them for wideband equipment14. Many products run at 10 dBm in Europe2, and makers sell regional variants at 10 and 20 dBm15,10,16; US rules allow more17.

Where sources disagree

Manufacturer and SIG range figures and independent field results differ by a factor of three or more2,8,3. Independent results also differ from each other: the hall testers note that room reflections, transmitter placement and the receiver all change the outcome6, the outdoor test found the crowd and line of sight decisive3, and an empty theatre was covered end to end by one ceiling-mounted transmitter7.

Sources also disagree on transmit power. The SIG advises the lowest power that reliably covers the intended area5,18, and one maker advises reducing power where many transmitters share a building11; a Swiss expert advises theatres to use maximum power and not to reduce it to limit range, because that puts less sensitive receivers at risk when the venue is full2.

What would settle it

Coverage measurements in occupied rooms of several kinds, with the transmitter position, height and power, and the receivers and firmware all recorded. IEC 60118-17, in preparation, is to include a coverage measurement method for single-transmitter systems19.

Planning while it is open

  • Mount high and keep the farthest seat within 20 to 30 m of a transmitter2,4.
  • Walk-test both empty and occupied5,3,7.
  • Ask for the power, receiver and conditions behind any advertised range; most published figures give no method, and the SIG handout gives no conditions at all8,10,11.
  • Record which receivers and firmware were used in each test, because results depend on them6.

Sources

  1. Auri coverage and install guide (application note UP3B609-01, rest-of-world edition). Listen Technologies and Ampetronic (Auri). Ampetronic, 17 April 2025. Manufacturer (Listen Technologies and Ampetronic) ↩︎ https://www.ampetronic.com/wp-content/uploads/UP3B609-01_RoW_Auri-Coverage-and-Install-Guide.pdf
  2. Bluetooth Auracast in theaters and event venues. Graf B (Pro Audito Schweiz). Proscenium no. 3, pp. 10-11, Swiss Association of Technical Stage and Event Industry; English reprint by the Center for Hearing Access, September 2026. Nonprofit advocacy (Pro Audito Schweiz, Swiss hearing-loss association) ↩︎ https://centerforhearingaccess.org/wp-content/uploads/Proscenium-Technical-article-Bluetooth-Auracast-in-theaters-and-event-venues-1.pdf
  3. Auracast practical test outdoors. Pro Audito Schweiz. Pro Audito Schweiz; English reprint by the Center for Hearing Access, 16 September 2026. Independent (Pro Audito Schweiz, Swiss hearing-loss association) ↩︎ https://centerforhearingaccess.org/wp-content/uploads/Pro-Audito-Schweiz-Auracast-practical-test-outdoors.pdf
  4. Can Bluetooth Auracast be used as an assistive listening system?. Pro Audito Schweiz. Pro Audito Schweiz (in German), 17 February 2025. Nonprofit advocacy (Pro Audito Schweiz, Swiss hearing-loss association) ↩︎ https://pro-audito.ch/news/kann-bluetooth-auracast-als-hoeranlage-eingesetzt-werden/
  5. Auracast simple transmitter best practices guide, version 3. Bluetooth SIG, 17 October 2025. Standards body (Bluetooth SIG, an industry association funded by its member companies, which owns the Auracast trademark) ↩︎ https://www.bluetooth.com/wp-content/uploads/2022/10/Auracast-Transmitter_Recommendations.pdf
  6. Auracast transmitter-receiver compatibility test (with data workbook). Pro Audito Schweiz, 6 October 2025. Independent (Pro Audito Schweiz, Swiss hearing-loss association; no manufacturer funding, test products lent free by manufacturers) ↩︎ https://pro-audito.ch/news/auracast-transmitter-receiver-compatibility-test/
  7. Test report: Auracast assistive listening system in a theatre. Pro Audito Schweiz. Pro Audito Schweiz (in German), 17 March 2025. Independent (Pro Audito Schweiz, Swiss hearing-loss association) ↩︎ https://pro-audito.ch/news/testbericht-auracast-hoeranlage-im-theater/
  8. What's the range of Auracast broadcast audio?. Bluetooth SIG, 28 July 2025. Trade body (Bluetooth SIG marketing material; the SIG is an industry association funded by its member companies and owns the Auracast trademark) ↩︎ https://www.bluetooth.com/wp-content/uploads/2024/01/2312_CES_Handout-Images_FINAL-range.pdf
  9. A new Bluetooth audio scan-to-listen experience. Bluetooth SIG Market Development. Bluetooth SIG, 17 February 2025. Trade body (Bluetooth SIG marketing material; the SIG is an industry association funded by its member companies and owns the Auracast trademark) ↩︎ https://www.bluetooth.com/wp-content/uploads/2025/03/02.20.25_Auracast_QR_Paper_FINAL.pdf
  10. AuraGate broadcast terminal datasheet. Aura by Opus (Opus Technologies). Opus Technologies, November 2025. Manufacturer (Opus Technologies) ↩︎ https://aurabyopus.com/wp-content/uploads/2025/11/AuraGate_Datasheet.pdf
  11. Infinium system controller and transmitter user manual (MAN 297B). Williams AV, 2026. Manufacturer (Williams AV) ↩︎ https://williamsav.com/wp-content/uploads/2025/08/MAN-297B-Infinium-Controller-Transmitter-BA-CT1.pdf
  12. Phonak EON: Connectivity excellence. Roh M (Sonova). Phonak Audiology Blog (Phonak Pro), 17 September 2026. Manufacturer (Sonova / Phonak) ↩︎ https://audiologyblog.phonakpro.com/phonak-eon-connectivity-excellence/
  13. ETSI EN 300 328 V2.2.2: wideband transmission systems; data transmission equipment operating in the 2.4 GHz band. ETSI Technical Committee ERM. European Telecommunications Standards Institute, 1 July 2019. Standards body (ETSI, the European Telecommunications Standards Institute) ↩︎ https://www.etsi.org/deliver/etsi_en/300300_300399/300328/02.02.02_60/en_300328v020202p.pdf
  14. Bluetooth Low Energy regulatory aspects document, version 1.01. Bluetooth SIG Regulatory Expert Group. Bluetooth SIG, 23 March 2023. Standards body (Bluetooth SIG, an industry association funded by its member companies, which owns the Auracast trademark) ↩︎ https://www.bluetooth.com/wp-content/uploads/2023/03/bluetooth-le-regulatory-aspects-document.pdf
  15. Auri TX2N / TX2N-D transmitter datasheet. Listen Technologies and Ampetronic (Auri). Ampetronic, July 2025. Manufacturer (Listen Technologies and Ampetronic) ↩︎ https://www.ampetronic.com/wp-content/uploads/UP3B603-2_Auri_TX2N_Transmitter_Datasheet.pdf
  16. Bettear CASTER user manual (firmware 1.0.8). Bettear. Bettear; copy hosted by the distributor Univox, 2026. Manufacturer (Bettear) ↩︎ https://univox.eu/wp-content/uploads/sites/2/2026/01/B-CASTER-User-Manual-1.0.8.pdf
  17. 47 CFR 15.247: operation within the bands 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz. US Federal Communications Commission. Electronic Code of Federal Regulations (eCFR), 1 April 2020. Government (US Federal Communications Commission) ↩︎ https://www.ecfr.gov/current/title-47/section-15.247
  18. How to build an Auracast transmitter: technical overview, version 3. Bluetooth SIG Market Development. Bluetooth SIG, 16 September 2026. Standards body (Bluetooth SIG, an industry association funded by its member companies, which owns the Auracast trademark) ↩︎ https://www.bluetooth.com/wp-content/uploads/2024/05/2403_How_To_Auracast_Transmitter.pdf
  19. IEC 60118-17 (in preparation): assistive listening system for hearing aid users based on 2.4 GHz audio streaming. IEC TC 29 WG 13. International Electrotechnical Commission, undated (read 13 October 2026). Standards body (International Electrotechnical Commission) ↩︎ https://tc29.iec.ch/tc-activity/standards-under-preparation/

Change log

  • Published with 19 sources.
  • Qualified the crowded outdoor result, including the search description, and identified the hall test funding.
  • Clarified hall reception ratings and replaced the opening cost claim with sourced placement guidance.

Cite this question

Equal Access Audio. “How far does one transmitter really reach in a full room?” Assistive Listening Knowledge Base. Updated 13 October 2026. https://assistivelisteningknowledgebase.org/questions/real-range/ (accessed the date you read it).

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