A method for identifying a mechanical impedance of an electromagnetic load may include generating a waveform signal for driving an electromagnetic load, the waveform signal comprising a first tone at a first driving frequency and a second tone at a second driving frequency. The method may also include during driving of the electromagnetic load by the waveform signal or a signal derived therefrom, receiving a current signal representative of a current associated with the electromagnetic load and a back electromotive force signal representative of a back electromotive force associated with the electromagnetic load. The method may further include determining amplitude and phase information of the current signal responsive to the first tone and second tone, determining amplitude and phase information of the back electromotive force signal responsive to the first tone and second tone, and identifying parameters of the mechanical impedance of the electromagnetic load based on the amplitude and phase information of the current signal and the amplitude and phase information of the back electromotive force signal.

The method and system uses ultrasound (US) transducers in contact with an inboard surface underwater portions of marine vessels or structures. By first digitally generating disruptive, multi-frequency, interfering US waveform signals (complex waveforms, typically replicating a Bessel function) and then converting the signals into analog, the transducers generate disruptive, multi-frequency, interfering US waveforms through the underwater portions of the marine vessels and structures which waveforms disrupt unwanted marine growth on the water-side of the vessel or structure. The digital signals, and also the analog signals, are complex waveform signals, typically produced with a Bessel function. The US transducers are either circular membrane transducers or surface transducers. A computer processor coupled to a memory, generates the complex waveform signals fed to the US transducers.

Transducer assemblies that can be used in acoustophoretic systems are disclosed. The acoustophoretic systems including the transducer assemblies and methods of operating the acoustophoretic systems are also disclosed. The transducer assemblies include a housing, a polymeric film attached to the housing, and a piezoelectric material attached to the polymeric film. The piezoelectric material is not attached to, and does not come in direct contact with, the housing. The piezoelectric material is configured to be driven by a drive signal to create a multi-dimensional acoustic standing wave. The piezoelectric material can be attached to the polymer film by an adhesive coating on the polymer film.

Aspects of the technology described herein relate to sensing a fingerprint of a subject via an ultrasound fingerprint sensor. Certain aspects relate to transmitting and receiving ultrasound data at multiple different frequencies to provide sensing data from different depths within the skin of the subject. Since different ultrasound frequencies are expected to penetrate a subject's skin to different degrees, sensing a finger at multiple ultrasound frequencies may provide information on different physical aspects of the finger. For instance, sound ultrasound frequencies may sense a surface of the skin, whereas other ultrasound frequencies may penetrate through one or more of the epidermal, dermal or subcutaneous layers. The ultrasound fingerprint apparatus may have utility in various applications, including but not limited to mobile electronic devices, such as mobile phones or tablet computers, a laptop computer or biometric access equipment.

A MEMS device may include a first electrode region; a first piezoelectric layer arranged over the first electrode region; a second electrode region arranged over the first piezoelectric layer; a second piezoelectric layer arranged over the first piezoelectric layer and the second electrode region; a third electrode region arranged over the second piezoelectric layer; a first input port coupled to the first electrode region and/or the second electrode region for providing a first electrical signal to the first piezoelectric layer to generate a first vibration in the first piezoelectric layer; a second input port coupled to the second electrode region and/or the third electrode region for providing a second electrical signal to the second piezoelectric layer to generate a second vibration in the second piezoelectric layer; and an output port configured to receive an output signal including a superposition of the first vibration and the second vibration.

Micromachined ultrasonic transducer (MUT) arrays capable of multiple resonant modes and techniques for operating them are described, for example to achieve both high frequency and low frequency operation in a same device. In embodiments, various sizes of piezoelectric membranes are fabricated for tuning resonance frequency across the membranes. The variously sized piezoelectric membranes are gradually transitioned across a length of the substrate to mitigate destructive interference between membranes oscillating in different modes and frequencies.

In one example, an apparatus comprises: a transducer, a driver circuit coupled to the transducer, a memory, and a controller. The memory is configured to store a power profile, the power profile including a mapping between power metrics and oscillation frequencies of the transducer, the power metrics being indicative of a power delivered to the transducer. The controller is coupled to the memory and the driver circuit, the controller configured to: obtain the power profile from the memory; determine a frequency of a driver signal based on the power profile; and provide the driver signal having the frequency to the driver circuit.

A wearable element is disclosed. In an embodiment a wearable element includes at least one piezoelectric element configured to vibrate so that a haptic impression of an acoustic signal is generated, wherein the wearable element is wearable on a body.

Broadband ultrasound transducers and related methods are disclosed herein. An example ultrasonic transducer disclosed herein includes a substrate and a first membrane supported by the substrate. The first membrane is to exhibit a first frequency response when oscillated. The example ultrasonic transducer includes a second membrane supported by the substrate. The second membrane is to exhibit a second frequency response different from the first frequency response when oscillated. The example ultrasonic transducer includes a third membrane supported by the substrate. The third membrane is to exhibit one of the second frequency response or a third frequency response different from the first frequency response and the second frequency response when oscillated. A shape of the first membrane is to differ from a shape of the second membrane and a shape of the third membrane.

A device for orthodontic treatment is disclosed. The device includes a first actuator configured to be attached to an orthodontic appliance and located proximate to a dentition. A second actuator is configured to be attached to the orthodontic appliance and located proximate to the dentition. A signal generator is in electrical communication with the first actuator and the second actuator. The signal generator is configured to provide a first drive signal to the first actuator and a second drive signal to the second actuator. In this way each actuator causes vibrational forces to be induced in the dentition. The actuators are configured such that the induced vibrational forces interfere with one another to cause an increased amplitude at a predetermined location in the dentition.