Tech Briefs

Spatial modulation is used to improve the detectability of an alert signal.

Auditory warning systems for human interfaces are often designed around criteria that depend primarily upon signal loudness. It is well understood from the auditory literature that, by making an alert signal substantially louder than the measured background noise level, one can insure that an alert signal will be detectable. Such auditory alert systems have been used in the aviation industry for a number of years in order to raise the awareness of the crew for terrain proximity, for example. However, if an alert signal amplitude is too loud, the alert signal may produce a “startle effect” that hinders performance in some high-stress situations.

This invention provides an alternative approach that uses other features — in particular, spatial modulation — to improve the detectability of an alert signal without substantially increasing the amplitude level of the alert signal beyond the background sound level.

This invention provides several different but compatible approaches to enhance the detectability of an alert signal. Binaural communication, using stereo earphones or loudspeakers with independent delivery systems, is preferred.

A prefix signal, associated with an existing alert signal, is provided that has a signal component in each of three or more selected frequency ranges, with each signal component in each of three or more selected levels at least 3 to 10 dB above an estimated background (non-alert) level in that frequency range. The alert signal may be chirped within one or more frequency bands. Also, if an alert signal moves, continuously or discontinuously, from one location to another over a short time interval, it introduces a perceived spatial modulation or jitter. A weighted sum of background signals adjacent to each ear is formed, and the weighted sum is delivered to each ear as a uniform background; a distinguishable alert signal is presented on top of this weighted sum signal at one ear, or distinguishable first and second alert signals are presented at two ears of a subject.

Applications can be found within aviation, naval vessels, vehicle stereo systems, shipping and transportation, control room monitoring, games, headsets for the visually impaired, and workers in loud environments.

This work was done by Durand R. Begault of Ames Research Center.

NASA invites companies to inquire about licensing possibilities for this technology for commercial applications. Contact the Ames Technology Partnerships Office at 1-855-NASA-BIZ (1-855-6272-249). Refer ARC-14556-1.

This Brief includes a Technical Support Package (TSP).

Enhanced Auditory Alert Systems (reference ARC-14556-1) is currently available for download from the TSP library.

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