The U.S. Patent and Trademark Office officially published a series of 45 newly granted patents for Apple Inc. today. In this particular report we cover two granted patents covering audio. The first covers a rotationally symmetric enclosure (HomePod) and the second covers Spatial 3D Audio for iDevices.

The first granted patent delves deeper into the multi-speaker system in filing titled "A rotationally Symmetric Speaker Array." In many respects the patent shares some of the technology used with Apple's new HomePod equipped with spatial awareness but on a much larger scale. It's a system that could automatically analyze the acoustics, adjusts the sound based on the speaker's location, and steer the music in the optimal direction of the listener.

Apple's invention covers a multi-way speaker array that includes one or more rings of transducers of different types. In one embodiment, the rings of transducers encircle the cabinet of the speaker array such that the speaker array is rotationally symmetric. This rotational symmetry allows the speaker array to be easily adapted to any placement within the listening area.

Apple's patent FIG. 8 shows the speaker array rotationally symmetric about a center axis.

Apple's granted patent 10,798,482 was published today by the US Patent and Trademark Office. For more on this, review our original patent report here.

Processing of Audio Signals for Spatial Audio

In June we learned that Spatial Audio is coming to Apple's next-gen AirPods Pro. In today's granted patent, spatial audio is discussed in terms of the iPhone and iPad.

Apple states that their patent relating to processing input audio channels for generating spatial audio can include receiving a plurality of microphone signals that capture a sound field. Each microphone signal can be transformed into a frequency domain signal. From each frequency domain signal, a direct component and a diffuse component can be extracted.

The direct component can be processed with a parametric renderer. The diffuse component can be processed with a linear renderer. The components can be combined, resulting in a spatial audio output.

The levels of the components can be adjusted to match a direct to diffuse ratio (DDR) of the output with the DDR of the captured sound field.

Apple further notes that linear processing algorithms beneficially place a light computational load on a processor. Spatial resolution of the audio output resulting from linear processing, however, can be severely restrained by the number of microphones employed to capture the sound field for recording. A high number of microphones may be needed to achieve a quality spatial resolution. Apple's patent provides a solution.

Apple's patent FIG. 1 below illustrates a diagram of a system or device that generates spatial audio.

(Click on image to Enlarge)

To be sure this is a complex patent and for engineers who are interested in digging deeper into the details, could find it under granted patent 10,798,511.

Apple's patent is broken down to a series of distinct chapters covering the following topics:

• Signal Flow
• Microphones
• Analyzer
• Direct Diffuse Component Separator
• Parametric Renderer
• Linear Renderer
• Band-Splitting
• Combiner, DDR Adjuster, Equalizer, and DDR/DRR Estimator
• Synthesizer
• Hybrid Process with Linear and Parametric Renderer
• Process of Generating Binaural Audio with Least-Squares Fit
• Process of Enforcing an Original DDR or DRR in Spatial Recording
• Process of Hybrid Linear and Parametric Processing

Check out the full granted patent here.