How Does Auracast Work? The Broadcast Flow, Step by Step

Figures on this page were checked September 2026. Protocol details follow the Bluetooth SIG’s public documentation.

The four-step flow

Our what-is explainer covers what Auracast is; this page walks the machinery. Four steps carry every broadcast, from a Galaxy phone sharing a podcast to an airport feeding a concourse.

1. The transmitter sends. A source device encodes audio (music, announcements, a phone’s output) over Bluetooth LE Audio and transmits it as a broadcast, using the LC3 codec. It also advertises: broadcast name, status and the details a listener needs, transmitted alongside the audio so devices in range can discover it.

2. Assistants scan. Devices running the assistant role — "smartphones, smartwatches, or hearing aid remotes" in the SIG’s enumeration — listen for those advertisements and assemble them into a list. The SIG’s comparison is the one everyone already knows: the interface works "similar to the UI commonly used to connect to Wi-Fi networks in public spaces."

3. The listener joins. Selecting a broadcast starts the stream on the receiver (hearing aids, earbuds, headphones, a speaker) with no pairing step. The broadcast was there to be joined; the selection is the whole interaction.

4. Everyone plays. The stream is one transmission, and the SIG is explicit about scale: an unlimited number of in-range receivers can join it, the same principle as a standard radio transmitter. The hundredth listener costs the transmitter nothing, which is the architectural fact behind every venue deployment.

Transmitters, assistants, receivers

The three roles are the grammar of the system. A transmitter creates broadcasts — a venue rack, a phone in Audio Broadcast mode, a TV adapter. An assistant discovers them — nearly always a phone, sometimes a watch or a hearing aid remote. A receiver plays them — hearing aids, earbuds, headphones, loudspeakers.

Devices commonly hold several roles at once. A Galaxy phone is an assistant (it scans and lists), often a transmitter (it can broadcast its own audio), and occasionally a receiver. Hearing aids stay in the receiver role — the SIG's assistant white paper is explicit that scanning is taken away from aids precisely because their batteries are small; a phone or remote does the scanning on their behalf. The roles are capabilities, not product categories — which is why a single phone can run a room’s audio and then join the airport’s feed on the same battery.

Open and encrypted broadcasts

A broadcast is open by default: anyone in range who scans can join. For content that should reach only its intended audience, the Public Broadcast Profile defines encrypted broadcasts: the stream is encrypted, and a receiver needs the Broadcast Code to decrypt it. The code travels however the host distributes it — a posted QR code, a printed password, a ticket — and the audio plays only on devices that have it.

The dependency runs one way, and it is worth stating plainly: the code gates decryption, not discovery. An encrypted broadcast can still appear in a scan list; what it does not do is play for devices without the code. Our what-is page covers the profile’s place in the LE Audio stack, and the Galaxy broadcast guide shows the phone-side version of the same lock.

Why it does not slow down

The counterintuitive part of the architecture is the load model. Wi-Fi trains everyone to expect degradation as users pile on — each device pulling its own stream competes for bandwidth. Auracast inverts the model: the transmitter sends one stream whether one receiver is listening or ten thousand, because the receivers are not calling in; they are tuned in. The SIG states it as a property of the design, and it is the reason a single phone can host a room’s audio or a venue can feed a stadium.

That is also why the assistive-listening case fits so naturally. A hearing aid is just another receiver — the thousandth one costs the transmitter nothing, arrives past the room’s acoustics, and plays through the listener’s own fitting. The receivers page covers the device side, and the venues tracker shows where the transmitters already are.

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