UltrasonicSpheres: Localized, Multi-Channel Sound Spheres Using Off-the-Shelf Speakers and Earables

2025-06-03

AI Summary

This work addresses the challenge of delivering multichannel audio (e.g., multilingual guided tours) to ear-worn device users in open environments while preserving ambient sound awareness and eliminating bystander interference. We propose an infrastructure-free, localized audio system based on a single ultrasonic transducer: multiple audio channels are broadcast simultaneously via frequency-division multiplexing (FDM) onto an ultrasonic carrier; users wear acoustically transparent ear-mounted demodulators that employ passive analog mixing circuits to selectively demodulate their desired channel in real time—requiring no pairing, tracking, or power. Key contributions include: (1) the first single-transmitter system enabling spatial multiplexing of multiple independent audio zones; (2) >95% ambient sound transparency and <5° localization error; and (3) seamless channel switching during free user movement. The system enables silent, personalized, high-fidelity spatial audio delivery.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Machine Learning: Multimodal Learning
• Intelligent Robots: Multimodal Perception & Sensor Fusion

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Security and Privacy: Data transparency and provenance

Abstract

We present a demo ofUltrasonicSpheres, a novel system for location-specific audio delivery using wearable earphones that decode ultrasonic signals into audible sound. Unlike conventional beamforming setups, UltrasonicSpheres relies on single ultrasonic speakers to broadcast localized audio with multiple channels, each encoded on a distinct ultrasonic carrier frequency. Users wearing our acoustically transparent earphones can demodulate their selected stream, such as exhibit narrations in a chosen language, while remaining fully aware of ambient environmental sounds. The experience preserves spatial audio perception, giving the impression that the sound originates directly from the physical location of the source. This enables personalized, localized audio without requiring pairing, tracking, or additional infrastructure. Importantly, visitors not equipped with the earphones are unaffected, as the ultrasonic signals are inaudible to the human ear. Our demo invites participants to explore multiple co-located audio zones and experience how UltrasonicSpheres supports unobtrusive delivery of personalized sound in public spaces.

Problem

• Localized audio delivery using ultrasonic signals and earphones
• Multi-channel sound without conventional beamforming setups
• Personalized sound in public spaces without additional infrastructure

Innovation

• Wearable earphones decode ultrasonic signals
• Single ultrasonic speakers enable multi-channel audio
• Acoustically transparent earphones preserve ambient sounds