Spatial Audio for Accessibility and Navigation

Module F: Applied frontiers. Lesson 11 of 20, 30 min.

Abstract

Spatial hearing is always on and works in every direction, which makes it a strong channel for assistive technology. This lesson covers sensory substitution, auditory navigation beacons, audio-tactile maps, hearing aids, safe listening and the cocktail-party benefit in group calls. It also covers the co-design and evaluation ethics that accessible design requires.

By the end you can

  • Explain how sensory substitution and virtual auditory beacons encode spatial information for blind and low-vision users
  • Implement a beacon that maps bearing and distance to pan, pitch and pulse rate in Python
  • Describe how directional microphones, binaural hearing aids and safe listening standards relate to spatial audio practice
  • Design an accessibility evaluation that follows co-design principles and research ethics

Most immersive audio work goes into making music and film more exciting. The same tools, though, can make the world easier to get around for people who cannot rely on sight, and they can make speech easier to follow for people with hearing loss. This lesson covers spatial audio as an assistive technology: sensory substitution, navigation beacons, accessible data, hearing health and group communication. It also covers the research ethics that come with building for and with disabled people.

Why spatial audio is an accessibility technology

Human hearing is always on, works in every direction, and is very good at telling where a sound comes from. You can hear things behind you, around corners and in the dark. As covered in How We Hear in 3D, the brain combines interaural time and level differences with spectral cues from the outer ear to place sources in space. For someone who is blind or has low vision, that ability is more than a pleasant extra. It is often the main way they sense their surroundings at a distance.

Assistive spatial audio takes advantage of this in three broad ways:

  • Substitution: turning information that normally arrives through one sense (for example, a camera image) into sound or touch.
  • Augmentation: adding virtual sounds, such as beacons, spatialized speech labels or earcons, on top of the real acoustic world.
  • Separation: using spatial cues to pull competing sounds apart, as when voices on a group call are placed at different positions so that each one is easier to understand.

These goals pull against each other. A navigation aid that fills the ears with virtual sound can hide the traffic noise a blind pedestrian depends on. A hearing aid that strongly favours sound from the front can make it harder to notice someone approaching from the side. Managing those trade-offs only works if the people who will use the system help define success, so co-design runs through the whole lesson.

The rest of this lesson, its lab and self-check are part of Academy Advanced, a paid course. See who has access.

Key readings

  • Loomis, J. M., Golledge, R. G., & Klatzky, R. L. (1998). Navigation system for the blind: Auditory display modes and guidance. Presence: Teleoperators and Virtual Environments, 7(2), 193–203.
  • Walker, B. N., & Lindsay, J. (2006). Navigation performance with a virtual auditory display: Effects of beacon sound, capture radius, and practice. Human Factors, 48(2), 265–278.
  • Bach-y-Rita, P., Collins, C. C., Saunders, F. A., White, B., & Scadden, L. (1969). Vision substitution by tactile image projection. Nature, 221, 963–964.
  • Bronkhorst, A. W. (2000). The cocktail party phenomenon: A review of research on speech intelligibility in multiple-talker conditions. Acta Acustica united with Acustica, 86(1), 117–128.
  • Dillon, H. (2012). Hearing Aids (2nd ed.). Thieme.