Visually impaired individuals, of whom there are upwards of 285 million worldwide, have long relied on objects like canes and guide dogs to assist with object detection and navigation. More modern systems often make use of more advanced technologies, such as an object detection device using ultrasonic transducers. Those devices may generate ultrasonic waves that produce an echo from a detected object. The echo is then detected and received by receivers that alert a visually impaired individual of objects in front of him or her. In those devices, because ultrasonic waves are undetectable by a human ear, a receiver, separate from the human ear, is needed to receive information about objects at a distance from a wearer.
Those sorts of devices often make use of the information encoded by the receiver to provide tactile or audio feedback to a user. For example, one “smart cane” employed provides a vibration to a user to indicate that a nearby object is detected in front of the cane user. Another wearable device embodied as glasses provides a vibration to a user to indicate that a nearby object is detected. Visually impaired users often find these vibrations (or sounds, provided by other object detection aids or wearables) to be annoying and distracting.
Human echolocation allows humans to detect objects in their environment by generating sounds and sensing echoes from the sounds created by objects in front of him or her. Those echoes are typically created by first actively generating sounds such as cane tapping, hand claps, finger snapping, a mechanical device such as a clicker or making clicking sounds with their mouths. People trained to orient by echolocation, often visually impaired individuals, may be able to interpret the sound waves that are reflected by nearby objects and accurately identify the location, size, distance and characteristics of the object. Visually impaired individuals may use this ability as a form of acoustic wayfinding, or navigating within an environment using auditory rather than visual cues. This echolocation ability is similar to active sonar and animal echolocation, which is employed by bats, dolphins, and whales (among others) to identify prey.
However, with respect to echolocation, it is often difficult for a person to generate a strong, targeted signal that is narrowly channeled to detect objects in front of him or her especially at a distance and above the waist. Instead, a mouth-click signal decays as the wave spherically propagates away from the source. As such, the signal has a limited range in which it can detect objects. Moreover, the echo signal is not very strong by the time it has attenuated on its way to a receiver, whether the receiver is electronic or a human ear.
Even moreover, an individual who uses his or her mouth to generate clicking sounds can experience echo masking. More specifically, because the mouth is in close proximity to the ears, the response echo may be “masked” by the original sound signal generated by the mouth-click. This can make it much more difficult for a person to hear the echo, let alone locate from where the echo is originating.
Parametric arrays have been used in the audio industry for some time to generate a narrow audio signal. As known in the art, a parametric array is a nonlinear transduction mechanism that uses ultrasonic transducers to generate a narrow beam of audio band frequency sound, through the mixing and interaction of high intensity ultrasonic soundwaves. Thus, beams of sound generated by parametric arrays take into account the combined effects of diffraction, absorption, and nonlinearity. As such, parametric arrays can create a strong directional sound beam with no side lobes in water and air.
A parametric array can fulfill the need to provide a device to assist visually impaired individuals with a more targeted, narrow signal for object detection. That way, the user has a better idea of what is in front of him or her at greater distances and at a higher elevation above the ground. The device should not require the use of headphones or head-mounted speakers, and it should not use distracting audio or tactile indicators to alert a wearer that an obstacle is detected in front of him or her. Furthermore, the device should be positioned such that the projection of the sound beam is away from, and in front of, the individual such that it does not mask the received echo. That way, more echo energy is received by the ears.