US 8,234,395 · Granted 2012-07-31

How Sonos Keeps Every Speaker in Perfect Time

Imagine trying to play the same song on ten different speakers in different rooms, but each speaker has its own internal clock running at slightly different speeds. This patent solves that nightmare by having one master device tell all the speakers exactly when to play each sound, so they stay perfectly in sync instead of creating an echo or delay.

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The plain-English version

What it protects

The claim covers a system where one central device distributes tasks to multiple independent devices over a network, with each task stamped with a specific execution time. What's protected here is the method of calculating the time difference between each device's local clock and the master clock, then using that difference to predict the exact moment each device should perform its action, so they all stay synchronized despite running on different internal clocks.

Why it matters

For a multi-room audio company like Sonos, this is foundational technology. Without synchronization across independent speakers, playing coordinated music across a home would be technically impossible—you'd hear delays and echoes that ruin the listening experience. The patent protects the specific engineering approach to keeping dozens of independently clocked devices locked in perfect timing, which became a core competitive advantage in the wireless speaker market.

Real-world use

When you play a song through a Sonos system in your living room, kitchen, and bedroom simultaneously, this patent's method is what ensures all three speakers start and progress through the song in perfect unison rather than seconds apart.

Original USPTO abstract

A system maintains synchrony of operations among devices that have independent clocking arrangements. The system includes a task distribution device that distributes tasks to a synchrony group of devices that perform the tasks distributed by the task distribution device in synchrony. The task distribution device distributes each task to the members of the synchrony group over a network. Each task is associated with a time stamp that indicates a time, relative to a clock maintained by the task distribution device, at which the members of the synchrony group are to execute the task. Each member of the synchrony group periodically obtains an indication of the current time indicated by its clock, determines a time differential between the task distribution device's clock and its respective clock and determines a time at which, according to its respective clock, the time stamp indicates that it is to execute the task.

Patent details

Publication number: US 8,234,395
Filing date: 2004-04-01
Grant date: 2012-07-31
Assignee: Sonos, Inc.
Inventor(s): MILLINGTON NICHOLAS A. J.
CPC class: G06F3/165

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