Sensory aids for the blind

Claim 1

A sensory aid for the blind comprising: an ultrasonic carrier signal oscillator which is periodically frequency swept, a head-set mounted transmitting transducer driven by a signal derived from the oscillator signal which radiates acoustic energy to a field of view, a two channel receiver system receiving the acoustic energy reflected from objects within said field of view, each channel including (a) a head-set mounted receiving transducer mounted with the transmitting transducer, the receiving transducers having divergent polar lobes which in combination with the polar lobe of the transmitting transducer simulate the characteristics of a normal human auditory system, (b) a muliplier having as one input the signal from the receiving transducer, (c) sound reproducing means driven by the output of said multiplier to provide one respective ear of the user with an audible signal the level of which is representative of the direction of the object with respect to the user, and common to both channels, a variable attenuator fed from the carrier signal oscillator which supplies said transmitting transducer and multiplier in each of said channels with a selected level of carrier signal as a common second input such that said audible signal has a frequency dependent on the distance between the respective receiving transducer and the object, the gain of both channels being controlled by the setting of said variable attenuator.