Abstract: Various implementations disclosed herein include devices, systems, and methods that track a state of a user's eye (e.g., position/orientation, gaze direction accommodation, pupil dilation, etc.) using coherence-based measurement (e.g., optical coherence tomography (OCT)). The coherence-based measurement may provide sub-surface information, e.g., depth, cross section, or a volumetric model of the eye, based on reflections/scattering of light (e.g., using relatively long wavelength light to penetrate into the eye tissue).

Abstract: A device that includes a microphone may be worn in or on an ear of a user. A microphone signal generated by the microphone may be processed to determine a heart activity of a user. An indication of a heart pathology may be detected by applying a predictive algorithm to at least the heart activity. Other aspects are described.

Abstract: Ultrasonic transducers may be used to track the position of an object. For example, eyewear such as a pair of glasses or other head-mounted device may use ultrasonic transducers to track a user's eye position and gaze direction. To increase positioning accuracy over short-range distances, an array of ultrasonic transducers with different center frequencies may be formed on a common substrate. The closely spaced ultrasonic transducers with relatively small individual bandwidths may be used to simulate a single transducer with a larger bandwidth. Control circuitry may adjust the phases of the transducers in the array to steer the ultrasonic signal beam towards the user's eye and/or to receive an ultrasonic signal beam from the direction of the user's eye. The control circuitry may use time delay and/or phase delay measurement techniques to determine a distance and/or direction to the user's eye using the ultrasonic transducer arrays.

Abstract: An ultrasonic wave is output from a speaker of a head-worn device. A microphone signal is obtained from a microphone of the head-worn device that senses the ultrasonic wave as it reflects off an ear of a user. Heart activity such as a heart rate of the user is determined based at least on the microphone signal. Other aspects are also described and claimed.

Abstract: A device that includes a microphone may be worn in or on an ear of a user. A microphone signal generated by the microphone may be processed to determine a heart activity of a user. An indication of a heart pathology may be detected by applying a predictive algorithm to at least the heart activity. Other aspects are described.

Abstract: An ultrasonic wave is output from a speaker of a head-worn device. A microphone signal is obtained from a microphone of the head-worn device that senses the ultrasonic wave as it reflects off an ear of a user. Heart activity such as a heart rate of the user is determined based at least on the microphone signal. Other aspects are also described and claimed.

Abstract: A signal representation method and apparatus for digital audio provides high quality low cost resampling by transferring the difficult interpolative computations into front-end (off-line) preprocessing, thereby reducing the load on the tone generating synthesis processor. This allows nearly perfect arbitrary-ratio resampling of stored waveforms at a fraction of the cost of prior art resampling. It also allows elimination of the prior art polyphase coefficient table since the waveform reconstruction information is fully contained within the polynomials. This is especially advantageous for execution on general purpose multi-tasking media processors.

Abstract: A method for resampling includes convolving a given set of samples with the impulse response function of a low-pass filter. In this method, values of the impulse response required for the convolution calculation are computed at the time of resampling from a segmented polynomial approximating the impulse response.

Abstract: A method and apparatus for producing a tone (e.g. for music) without use of a waveform memory and using a feedback loop. The feedback loop includes a waveform generator which calculates, in real time, a parabolic approximation to a sine wave. The feedback loop includes a delay phase differencer to eliminate hunting. The output waveform from the feedback loop is provided to a sine function generator which approximates a sine value using a third order polynomial, to provide the output tone.

Abstract: A system and method for stack-based processing of multiple real-time tasks operates on a net list of tasks which operate essentially simultaneously with system resources shared between tasks in a dynamic configuration. This system and method operate to control dispatching of messages which activate signal processing tasks, sequencing of processes activated by the messages and management of signal flow. Tasks are dynamically activated and deactivated in accordance with the specification by the net list by manipulating the task signals on the stack, thereby substantially reducing high-speed memory requirements of the system.

Abstract: A method for resampling includes convolving a given set of samples with the impulse response function of a low-pass filter. In this method, values of the impulse response required for the convolution calculation are computed at the time of resampling from a segmented polynomial approximating the impulse response. In one embodiment, the method is applied to provide musical tones of various pitches from a stored waveform.

Abstract: In a sound (music) synthesis system, a transition between levels of a sound parameter (e.g. volume) is synthesized by fitting a cubic (third degree) spline function between two discontinuous parameter levels. This advantageously eliminates any sound artifacts (pops or clicks) which would otherwise be present due to abrupt changes in the parameter. The cubic spline is fitted (interpolated) to match both the parameter value and its derivative with respect to time at each of the adjacent parameter levels on either side of the transition. The transition thus is advantageously kept brief and in addition it is possible to deal with the situation when the parameter dynamically changes during the transition period, again without causing undesirable sound artifacts.