Abstract: This application describes methods and apparatus for remotely indicating a location of interest in an area, for instance the location of an event in the area. The method comprises positioning an acoustic source at the location of interest, activating the acoustic source to produce a predetermined acoustic output and performing distributed acoustic sensing on at least one optical fibre deployed at least partly in the area. The acoustic source thus acts as an acoustic marker which can be remotely detected by the distributed acoustic sensor. The acoustic signals detected by the distributed acoustic sensor are therefore analysed to detect said predetermined acoustic output and determine the location of the acoustic source. The method is particularly applicable to transport networks already provided with optical fibre along the length of the network and can be used to indicate the location of work parties or emergencies.

Abstract: An acoustic positioning device includes an acoustic emitter and receiver. The device emits a sequence of at least one first acoustic signal (S1) and one second acoustic signal (S2), separated by a time interval T, and to receive and measure the arrival phase ?1 of S1 and the arrival phase ?2 of S2. The device measures a relative displacement between the acoustic emitter and the acoustic receiver and determines the approximate difference (R2?R1)AUX between the distance R1 traveled by S1 between the acoustic emitter and receiver, and the distance R2 traveled by S2 between the acoustic emitter and the acoustic receiver, and calculates the relative displacement (R2?R1) between the acoustic emitter and the acoustic receiver as a function of the approximate difference (R2?R1)AUX, of the time interval T and of the arrival phases ?1, ?2 respectively of S1 and of S2.

Abstract: A method for measuring three-dimensional coordinates of a probe center includes: providing a spherically mounted retroreflector; providing a probe assembly; providing an orientation sensor; providing a coordinate measurement device; placing the spherically mounted retroreflector on the probe head; directing the first beam of light from the coordinate measurement device to the spherically mounted retroreflector; measuring the first distance; measuring the first angle of rotation; measuring the second angle of rotation; measuring the three orientational degrees of freedom based at least in part on information provided by the orientation sensor; calculating the three-dimensional coordinates of the probe center based at least in part on the first distance, the first angle of rotation, the second angle of rotation, and the three orientational degrees of freedom; and storing the three-dimensional coordinates of the probe center.

Abstract: Signals are received, over a range of angles, at an input of a device. The signals include a primary signal with a principal direction of arrival and an interfering signal with a respective interfering direction of arrival at the input. Measurements are determined for the received signals over the range of angles. Each measurement relates to a particular angle and indicating the energy of the received signals which are received from the particular angle. For each angle over the range of angles, a value is removed from the measurement for that angle, the value being based on the minimum of: (i) the energy of the measurement for that angle, and (ii) the energy of a corresponding measurement for a corresponding angle mirrored around the principal direction of arrival, whereby the remaining values of the plurality of measurements are indicative of said at least one interfering direction of arrival.

Abstract: Techniques for tracking a current location of a user are described. According to various embodiments, an ambient noise signal proximate to a user device is detected using a microphone. Audio sample information may be accessed, where the audio sample information identifies various audio samples and, for each of the audio samples, a source of the corresponding audio sample. Thereafter, a specific audio sample corresponding to the ambient noise signal may be identified. Moreover, a current location of the user device may be determined, based on the source of the specific audio sample.

Abstract: A direction of arrival (DOA) estimation device and method are provided, in which the DOA estimation device includes a sensor unit configured to detect a signal and comprising two or more sensors to output sensor signals as a detect signal in response to the detected signal, and a controller configured to calculate statistical distribution data indicative of statistical distribution of each of the sensor signals outputted from the two or more sensors, respectively, retrieve statistical distribution data indicative of statistical distribution of source signal which is non-stationary signal entrained in the signal of the calculated statistical distribution data, and estimate DOA of the source signal based on the retrieved statistical distribution data.

Abstract: The present invention relates to a method for determining an acoustic property of an environment. According to the method a sound signal and at least two reflection signals of the sound signal (are received, and for each of the reflection signals a time difference between a time of reception of the sound signal and a time of reception of the respective reflection signal is determined. Furthermore, for each of the reflection signals, an angle between a reception direction in which the sound signal was received and a reception direction in which the respective reflection signal was received is determined. Based on the determined time differences, the angles and predetermined constraints defining arrangement constraints of the sound reflecting surfaces an arrangement of the sound-reflecting surfaces is determined.

Abstract: A system and method is provided for resolving a pivot point via touchless interaction. It applies to situations where one end of a rigid object is inaccessible but remains stationary at a pivot point, while the other end is free to move and is accessible to an input pointing device. As an example, the rigid object can be a leg bone where the proximal end is at the hip joint and the distal end is at the knee. The system comprises a wand and a receiver that are spatially configurable to touchlessly locate the pivot point without contact. The receiver tracks a relative displacement of the wand and geometrically resolves the location of the pivot point by a spherical mapping. The system can use a combination of ultrasonic sensing and/or accelerometer measurements. Other embodiments are disclosed.

Abstract: Methods of and systems for determining a location of a mobile device using transmitted audio signals is provided. In an embodiment, meta data included in the audio signals may also be used. In an embodiment, a characteristic, such as a received signal strength, may be measured to determine the location of the mobile device.

Abstract: A method of acoustic positioning determination includes detecting a temperature gradient profile across a depth of water, determining a level of a thermal boundary between an upper temperature level and a lower temperature level, and determining a distance from the thermal boundary to position the acoustic positioning device and positioning the acoustic positioning device at that location.

Abstract: Movements of objects within a space are adaptively detected by emitting ultrasound waves into the space and detecting reflections of the ultrasound waves, determining locations of objects within the space based on the ultrasound reflections, and determining real-time movements of the objects based on, in certain embodiments, (i) amplitude differences between amplitudes of echoes in a current wave cycle and an average amplitude over a plurality of wave cycles and (ii) elapsed times of the ultrasound reflections associated with the amplitude differences.

Abstract: A computationally implemented system and method that is designed to, but is not limited to: electronically determining positioning status of one or more portions of one or more humans relative to one or more locations of demodulation of one or more acoustic ultrasonic signals into one or more acoustic audio signals said one or more acoustic ultrasonic signals originating from a portable electronic device; and electronically alerting said one or more humans from said portable electronic device regarding said positioning status of one or more portions of one or more humans relative to one or more locations of demodulation of one or more acoustic ultrasonic signals into one or more acoustic audio signals when said positioning status includes a first characterization. In addition to the foregoing, other method aspects are described in the claims, drawings, and text forming a part of the present disclosure.

Abstract: The present invention relates to a method for determining the location of a firer, furthermore a system and method for route planning (700). The system is arranged to be mounted on a moving object. The system comprises a position module (702), a firer location estimation module (704) and a route planning module (705). The position module (702) is arranged register the present position of the moving object at request and to determine the travel path of the moving object during a predetermined time period preceding the request, wherein the present position represents a target position for firing. The firer location method and the estimation module (704) is arranged to estimate the location of a firer based on the registered position and the determined travel path and based on map data (701) comprising 3D geographical coordinates data. The route planning module (705) arranged to plan a route of the object based on the determined location of the firer.

Abstract: A system and method of touchless interaction is provided for resolving a pivot point of an object where direct placement of a sensor at the pivot point is not practical. It applies to situations where the pivot point of a rigid object is inaccessible but remains stationary, while the other end is free to move and is accessible. The system maps the object's pivot point by way of an external sensor that detects constrained motion of the rigid object within a hemispherical banded boundary. It can also detect a geometric pattern and acceleration during the constrained motion to compensate for higher order rotations about the pivot point. Other embodiments are disclosed.

Abstract: A distance sensor for vehicles is provided which includes a sensor device and an electric connector for an electrical connection between the sensor device and a mating connector. The connector includes at least one first terminal pin and at least one second terminal pin. The first terminal pin has a first section leading to the sensor device and a second section extending toward an inlet opening of the connector. The second terminal pin has a first section leading to the sensor device and at least two branched second sections extending toward the inlet opening of the connector. Specifically, the second terminal pin is shaped to provide two-pin plugs, thereby permitting the size of the connector to be reduced, which facilitates ease of installation of the distance sensor to, for example, a bumper of the automotive vehicle.

Abstract: A system for determining the origin and trajectory of a gunshot includes spaced sensor nodes and a base station. A method for determining the origin and trajectory of a gunshot includes the steps of, at the nodes, sensing acoustic signals, converting the acoustic signals into digital signals, separating the digital signals into segments, calculating a time of arrival of each segment, and extracting features from each segment, and then at the base station identifying each time of arrival as a main shock wave or a main muzzle blast time of arrival from the features, and computing the trajectory from the main shock wave times of arrival. The computed trajectory includes velocity and acceleration. The method also includes computing, at the base station, the origin from the main muzzle blast times of arrival.

Abstract: Apparatus configured for processing of both audible and ultrasonic sound inputs, including a sensor with a frequency response spanning both audible and ultrasonic frequencies, and processing electronics configured to separate the audible and ultrasonic input frequencies for independent use. Apparatus configured for processing of both audible and ultrasonic sound inputs, including a sensor with a frequency response spanning both audible and ultrasonic frequencies, and processing electronics configured to process each one of the audible and ultrasonic input frequencies independently. Related apparatus and methods are also described.

Abstract: An indoor ultrasonic location tracking system that can utilize standard audio speakers to provide indoor ranging information to modern mobile devices like smartphones and tablets. The method uses a communication scheme based on linearly increasing frequency modulated chirps in the audio bandwidth just above the human hearing frequency range where mobile devices are still sensitive. The method uses gradual frequency and amplitude changes that minimize human perceivable (psychoacoustic) artifacts derived from the non-ideal impulse response of audio speakers. Chirps also benefit from Pulse Compression, which improves ranging resolution and resilience to both Doppler shifts and multi-path propagation that plague indoor environments. The method supports the decoding of multiple unique identifier packets simultaneously. A Time-Difference-of-Arrival pseudo-ranging technique allows for localization without explicit synchronization with the broadcasting infrastructure.

Abstract: A method and system for determining a real-time location of an object or person in a facility using low frequency magnetic induction positioning is disclosed herein. Each of the plurality of low frequency receivers is configured to receive a signal packet from a low-frequency magnetic induction transmitter, decode the signal packet, and estimate a distance from the low-frequency magnetic induction transmitter to the low-frequency receiver based on the decoded signal packet.

Abstract: Provided is an electronic device including a modulation unit (22) that modulates a sound signal to a modulation wave for a parametric speaker; an oscillator (12) to which the modulation wave is input; an equalizer (26) that corrects a frequency characteristic of a sound wave that is demodulated by the modulation wave; and a control unit (20) that selects a carrier frequency of the modulation wave and changes setting of the equalizer (26) on the basis of the selected carrier frequency. Thus, it is possible to provide the electronic device capable of correcting the frequency characteristic of the sound wave that is demodulated, for each carrier frequency of the modulation wave.

Abstract: An ultrasonic sensor has: a diaphragm that includes at least two partial regions for emitting and/or receiving ultrasonic signals, the two partial regions possessing different resonance characteristics; and at least one electromechanical transducer coupled to the diaphragm, to which transducer a control signal having at least two different control signal frequencies is applied. In this context, a first control signal frequency is in the range of a resonant frequency of a first partial region of the diaphragm, and a second control signal frequency is in the range of a resonant frequency of a second partial region of the diaphragm. Alternatively, two electromechanical transducers are used, which are coupled to a diaphragm and have different resonance characteristics.

Abstract: Mobile devices with ultrasound ranging are disclosed. A mobile device with ultrasound ranging can include a multifunctional component capable of performing multiple functions in the device, where the component can function as an ultrasound transmitter capable of transmitting an ultrasound signal to a proximate device. In some examples, the component can also function as a power button capable of powering the device up and down. In some examples, the component can also function as a home button capable of causing a home page to display on the device. The mobile device can further include an ultrasound receiver capable of receiving an ultrasound signal from the proximate device, where the device can calculate a range of the proximate device based on a time lapse associated with the received ultrasound signal.

Abstract: A system and a method for a blind direction of arrival estimation is provided for a nonlinear 1-dimensional array of M receivers of J<M unknown signals transmitted through an unknown channel and subject to Gaussian noise. The method overcomes the conditions of that signals be disjoint in the time-frequency domain and/or statistically independent. A likelihood function evaluates a probability for the directions of arrivals. A weighting and regularization scheme selects relevant frequency components. A joint likelihood function of all frequencies is interpreted as a cost or objective function. The time domain is included into the estimation procedure by using a particle filter that operates on the constructed likelihood function and a simple transition kernel for the directions.

Abstract: Disclosed is a user-interface target motion analysis (TMA) method using two-dimensional parameter control and speed zoom, and the method includes a first step of displaying a user-interface target motion analysis screen capable of selecting an input method; a second step of receiving the input method of a user; a third step of simultaneously calculating a speed and a course by speed zoom or simultaneously calculating a course and an initial range; a fourth step of calculating an initial range or a speed by speed zoom that is not calculated in the third step; and a step of generating a result of the target motion analysis using the parameters inputted through the first to fourth steps.

Abstract: An improved method and system for removing time-varying Doppler shifts and the effects of turbulence from data comprising at least one processor operating to estimate the average instantaneous frequency; reduce or remove noise from the state space variables estimates describing the frequency of the target; compensate for the motion of the target to obtain motion compensated data and increase the coherency of the data, and reduce or remove the noise from the state space variables describing the frequency of the target using a filter or smoother. Alternately, the method and system may comprise at least one processor operating to estimate the average instantaneous frequency of the first harmonic of a moving target; the average instantaneous frequency being inputted into an error reduction subroutine; using state space estimates of the frequency, calculating a time warping to remove the effect of the Doppler shift; and focusing the data using a modified PGA.

Abstract: A method and device for aliasing ultrasound to produce audio tones includes a microphone circuit to receive an ultrasonic burst from at least one emitter in an environment. An analog-to-digital converter can convert the ultrasonic burst into a digital waveform. A digital signal processor can: provide an ultrasonic sampling frequency, alias the digital waveform with the ultrasonic sampling frequency to provide an audio signal, and detect the audio signal frequency. An amplitude of multiple audio signals can be used to locate the device within the environment.

Abstract: An apparatus for resolving an ambiguity from a DOA estimate includes a DOA estimate analyzer for analyzing the DOA estimate to obtain a plurality of ambiguous analysis parameters by using a bias information, the bias information representing a relation between a biased and an unbiased DOA estimate, and an ambiguity resolver for resolving the ambiguity in the plurality of ambiguous analysis parameters to obtain a non-ambiguous resolved parameter.

Abstract: A method for determining the location of an impact on a surface (1) comprising N acoustic sensors (2a, 2b, 2c), transmitting a sensed signal si(t) to a processing unit (4) comprises the following steps (a) computing P intercorrelation products (b) calculating P inverse Fourier transforms p?ij (u) (c) computing for each area k, Pk(u)=?P?ij (u??ijk); d) finding k0, where a characterizing value of Pk0 (u) is greater than a given threshold value.

Abstract: A sound direction estimation device includes a transfer function storage unit configured to store transfer functions of sound sources in correlation with directions of the sound sources, a calculation unit configured to calculate the number of classes to be searched and a search interval for each class based on a desired search range and a desired spatial resolution for searching for the directions of the sound sources, and a sound source localization unit configured to search the search range for every search interval using the transfer function, to estimate the direction of the sound source based on the search result, to update the search range and the search interval based on the estimated direction of the sound source until the number of classes calculated by the calculation unit is reached, and to estimate the direction of the sound source.

Abstract: A system and method for compensating ultrasonic sensors mounted on a vehicle for speed of sound variations. The ultrasonic sensor is operatively coupled to a power train control module having a pressure sensor that continuously monitors atmospheric pressure and a controller configured for computing a compensated speed of sound using the monitored atmospheric pressure. The ultrasonic sensor sends an ultrasonic wave and determines the time lag in receiving the reflected ultrasonic wave from an object. Subsequently, the ultrasonic sensor generates a signal corresponding to the relative distance between the vehicle and the object using the compensated speed of sound and the time lag.

Abstract: A method of filtering noise in a three-dimensional position measurement system comprising receiving distance data representative of the respective distances between at least four spatially dispersed known points and an unknown point, performing triangulation calculations to determine at least two solutions to the three dimensional position of the unknown point relative to the known points, calculating a symmetrical bounding surface such as a sphere or cube which just encloses the said solutions, comparing the maximum dimension of the bounding surface with a first predetermined error threshold, and if the maximum dimension is less than the first error threshold, determining the center position of the bounding surface and outputting the center position as a noise-filtered position for the unknown point.

Abstract: A method and system is described for reducing unwanted noise components/interfering targets detected through an ambiguous beam-steer direction, such as the ambiguous ‘back-lobe’ of a sensor array. A pressure sensor array 52 and a plurality of pressure gradient sub-arrays 541-N are beamformed individually at processing stages 56, 581-N to derive signals indicative of directional responses, one from each group or sub-group. The signals are scaled and weighted (60, 620-N) and processed to define a cardioid beam with nulls pointing in the ambiguous beam-steer direction.

Abstract: A method for indoor navigation in a venue derives positioning of a mobile device based on sounds captured by the microphone of the mobile device from the ambient environment. It is particularly suited to operate on smartphones, where the sounds are captured using microphone that captures sounds in a frequency range of human hearing. The method determines a position of the mobile device in the venue based on identification of the audio signal, monitors the position of the mobile device, and generates a position based alert on an output device of the mobile device when the position of the mobile device is within a pre-determined position associated with the position based alert.

Abstract: A computer-readable recording medium storing an estimation program for causing a computer to execute a process, the process includes: executing sound image localization processing for each of pieces of sound data output by a plurality of sound sources; and specifying, on the basis of a change in orientation of a listener caused in accordance with the sound image localization processing, at least one of the plurality of sound sources related to the listener.

Abstract: An ultrasonic locationing system includes an emitter operable to emit at least two ultrasonic frequency tones sequentially in one ultrasonic burst. These tones, which may contain multiple frequency components, define a unique regional address. A mobile device with a microphone is operable to receive the ultrasonic burst and have a processor determine the sequential tones. A location of the device can be found from a table of predefined tones assigned to known regional addresses.

Abstract: A receiving device captures sounds signals (e.g., ultrasonic) from multiple sound signal sources, selects the sound signals satisfying a reliability condition for use in determining an initial position of the receiving device relative to the corresponding sound signal sources, determines the initial position of the receiving device using multilateration of the selected sound signals, and updates the current position of the receiving device as the reliability of individual sound signals varies in the presence of dynamically changing environmental interference, multipathing, and movement between the receiving device and the sound signal sources.

Abstract: A locating device for locating at least one apparatus which is arrangeable on board a transport unit, for example an aircraft, a locating system having such a locating device and at least one apparatus to be located, an aircraft having a locating system of this type, an associated method for locating at least one apparatus which is to be located and is arrangeable on board a transport unit, for example on board an aircraft, and a computer program for carrying out the method. The locating device includes a detecting unit for detecting a wireless audio signal transmitted by the apparatus to be located; and a computing unit for determining the distance of the apparatus to be located from the detecting unit based on the wireless audio signal and on a first information signal assigned to the audio signal and transmitted via a first deterministic data connection.

Abstract: A method of obtaining information about the positions of sources in a marine seismic source array, comprises: determining respective notional signatures for m selected seismic sources, where m<n, where n is the number of sources of the array actuated to generate an output; and obtaining information about the travel between one of the m selected seismic sources and one of the n?m unselected seismic sources from the determined notional signatures. The m seismic sources are selected as sources whose positions, relative to one another, are expected to be close to their nominal positions. The effect of the n?m unselected seismic sources is ignored in the calculation of the nominal signatures for the m sources, and this gives rise to anomalies in the nominal signatures for the m sources. The determined travel time may be converted to a distance, so that information about the positions of the n?m unselected seismic sources may be obtained from the anomalies.

Abstract: A plurality of spatially located ultrasound beacons are provided in known locations within a distributed communications system. Each of the ultrasound beacons is configured to emit ultrasound pulses that can be received by client devices in ultrasound communication range of the ultrasound beacons. The client devices are configured to analyze the received ultrasound pulses from the beacons to determine their time-difference of arrival and as a result, their location in the distributed communications systems. Use of ultrasound pulses can provide greater resolution in location determination of client devices since ultrasound waves experience strong attenuation in building walls, ceilings, and floors, thus avoiding detection of ultrasound waves from other ultrasound beacons not located in proximity to the client devices.

Abstract: An approach is provided for providing location information of user devices based on signal frequencies of transmitters. The positioning platform processes and/or facilitates a processing of one or more signals, from one or more transmitters, captured at one or more user devices to determine one or more frequencies of the one or more signals. Next, the positioning platform determines device location information of the one or more user devices based, at least in part, on the one or more frequencies.

Abstract: The present invention teaches acoustic absolute position encoders and methods for deploying the same. The encoder has a moving member with a mechanical contacting portion, and a stationary member associated with the moving member. Reed elements are mounted on the stationary member such that they are mechanically engaged by the contacting portion of the moving member as the latter moves linearly or rotates. The reed elements generate sound tones in response to transient contact with the contacting portion. A receiver receives the tones and an acoustic processing circuit determines the absolute position of the moving member based on the sound tones.

Abstract: A method and apparatus for processing sound from a sound source. The sound from the sound source is detected. Harmonics in the sound from the sound source are identified. A distance to the sound source is identified using the harmonics and a number of atmospheric conditions.

Abstract: A method and an apparatus for passive determination of target parameters by directionally selective reception of sound waves emitted or transmitted from a target, by an arrangement (24) of underwater sound sensors of a sonar receiving installation from estimated bearing angles determined from estimated positions of the target, and bearing angles measured at the measurement point by the arrangement (24). A bearing angle difference between measured and estimated bearing angles is iteratively minimized and, when the minimum is reached, the target parameters are used for an optimized solution for outputting target position, course, range and/or velocity and they are updated during each processing cycle in a series of successive processing cycles.

Abstract: A method includes enabling a power supply of a ground sensor device to provide power to one or more components of the ground sensor device based on one or more rotations of a rotor of the ground sensor device.

Abstract: The invention relates to a method for estimating the contents of particulate solids in a solid container, comprising the steps of: a) providing a percussion device; b) hitting the surface of the container on it outside with said percussion device at predetermined distances along the height of the container; c) recording the sound created by said percussion; d) identifying the sound generated by each recorded percussion at the percussion time within a plurality of percussions; e) applying a analysis algorithm to a digital representation of the sounds identified in d above; and e) determining the heights of the container that is filled with particulate material by locating the height at which the value resulting from the analysis of each percussion changes from a high to lower value, wherein a higher value indicates an empty portion of the container, and a lower value indicates a filled portion of the container.

Abstract: A method for increasing a bearing accuracy of a receiver assembly includes providing a receiver assembly which receives sound waves to determine reception signals. The reception signals determine direction signals of a reception direction. Frequency lines of a frequency of a frequency range comprising an amplitude value are attributed to a reception direction based the direction signals. A directional function is formed for each frequency. Each directional function is transformed into a spectral range to obtain a first spectral function comprising first spectral function arguments. The first spectral function are filled with other spectral function arguments between middle spectral function arguments of the first spectral function arguments to obtain filled first spectral arguments. The other spectral function arguments have a respective value of zero or a range of zero. Each of the filled first spectral functions are transformed back from the spectral range to an interpolated first directional function.

Abstract: A tracking system for use with a pipeline includes a scraper having signal generation capability for generating acoustic signals, a plurality of acoustic pressure sensors positioned at intervals along the path traveled by the scraper, and a plurality of local processors positioned at intervals along the path traveled by the scraper. Each of the local processors is in communication with a respective acoustic pressure sensor. A central processor is in communication with the local processors and determines the location of the scraper using time-stamped acoustic signals received by the pressure sensors and a speed of sound in a fluid within the pipeline.

Abstract: The present invention relates to a method and associated apparatus for the detection and identification of a sound event comprising collecting audio data from an acoustic sensor; processing the collected audio data to determine periodicity of the sound, processing the collected audio data to isolate transient and/or non-linear sounds and processing the collected audio data to identify frequency modulated pulses, in parallel to produce three output data sets; and combining and comparing the output data sets to categorise the sound event as being mechanical, biological or environmental. The method is particularly useful for detecting and analysing sound events in real time or near real-time and, in particular, for sonar applications as well as ground (including seismic) monitoring or for monitoring sound events in air (e.g. noise pollution).

Abstract: A wind direction detecting system of electronic apparatus includes an audio collecting module, a direction detecting module, and an analyzing module. The audio collecting module controls an audio collector to collect audio data at predetermined time intervals. The direction detecting module controls a direction sensor to detect a facing direction of electronic apparatus in relation to terrestrial magnetism each time the audio collector collects audio data. The analyzing module determines the facing direction where a greatest amplitude of the graph of audio data is recorded as the wind direction.

Abstract: A submarine homing system includes an acoustic emitter configured to emit an acoustic signal comprising at least two narrow-band tones, each narrow-band tone having a respective predetermined center frequency. An acoustic receiver is configured to receive the acoustic signal from the acoustic emitter, and produce one or more receiver signals. A processor is operatively connected to the acoustic receiver. The processor is configured to process the receiver signals to calculate a direction between the acoustic receiver and the acoustic emitter.