EarCase: Sound Source Localization Leveraging Mini Acoustic Structure Equipped Phone Cases for Hearing-challenged People

Sound source localization is vital for daily tasks such as communication or navigating environments. However, millions of adults struggle with hearing impairment, which limits their ability to identify the direction and distance of sound sources. Traditional methods for sound spatial sensing, such as microphone arrays, are not suitable for resource-constrained IoT devices like smartphones due to power consumption or hardware complexity. To overcome these limitations, this paper proposes EarCase, an alternative scheme that utilizes commercial smartphones with only two microphones to recognize 3D acoustic spatial information. EarCase draws inspiration from the human auditory system, where two ears amplify minute differences in acoustic signals to help pinpoint sound sources. This ability can be regarded as a response function trained through a large amount of sound source information, which can be used to extract spectral cues from a sound source position to the ears drums. We imitate this effect by designing a smartphone case with perforated mini-structures covering the microphones to help the smartphone infer the location of the sound source. Sound waves that pass through the mini-structure will undergo unique changes in diffraction at the hole, amplifying directional information similar to ears. Our scheme uses the top and bottom microphones to eliminate noises and multi-path effects, making the design robust to different sound sources in varying environments. By using only built-in microphones and low-cost phone cases, EarCase provides an accessible tool to enhance the quality of life for hearing impaired individuals. Extensive experimental results show that EarCase achieves high accuracy in localizing sounds, with a mean error of 3.7 degrees at a distance of 200cm and 96% accuracy for real-world sounds (e.g., car horns).