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How to design Auracast earbuds

From https://assistivelisteningknowledgebase.org/evidence/sig-2025-earbuds-guide/ · record checked 13 October 2026

  • Bluetooth SIG Market Development
  • Bluetooth SIG (technical overview, version 1.1)

Standards body (Bluetooth SIG, an industry association funded by its member companies, which owns the Auracast trademark)

Summary

Design principles for Auracast receivers, using earbuds as the example; the SIG says they apply equally to hearing aids, headphones, speakers and soundbars.

Key findings

  • All receivers must be able to render within a presentation delay of 40 ms, the default. Receivers built to the hearing aid (HAP) or telephony and media (TMAP) profiles should handle any value from 20 to 40 ms. A receiver given a value outside its range should use the nearest value it supports rather than reject the stream.
  • When a transmitter sets the immediate-rendering flag for live content, ear-worn receivers should use their lowest supported delay; speakers and devices that render at a distance are advised not to support the flag.
  • Receivers are not required to handle multiplexed streams or to down-mix left and right to mono, so a transmitter serving listeners who need mono should send a separate mono stream.
  • The head absorbs 2.4 GHz signals strongly, so left and right earbuds or hearing aids cannot rely on a Bluetooth link between them; they stay on the same stream through an assistant or a proprietary link.
  • A receiver can read from a broadcast's announcement whether it is encrypted and whether a 16 or 24 kHz stream is on air; if not, the user may need to ask for one. Receivers are expected to handle four retransmissions of each packet and should support packet loss concealment.
  • Section 2.6.3 recommends receiving only the BISes needed for playback and switching the receiver off during other BIS transmissions to avoid needless battery use. It recommends a separate mono subgroup where mono is needed because stereo downmixing is optional.

Limits

Design recommendations, not test results; how far shipping products follow them is not reported.

Read the original

www.bluetooth.com/wp-content/uploads/2024/05/2403_Auracast_Earbuds.pdf

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Cited in

Cite this source

Bluetooth SIG Market Development. How to design Auracast earbuds. Bluetooth SIG (technical overview, version 1.1). 6 February 2025. https://www.bluetooth.com/wp-content/uploads/2024/05/2403_Auracast_Earbuds.pdf (accessed 13 October 2026).

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