A pressure wave-generating device having a support and a heating element film that is disposed over the support and that is configured to generate heat by energization, and the heating element film has a porous metal structure.

Systems and methods for the reduction of noise arising from the fluid mechanics of the aerodynamic interactions of the relative motion of solid elements with a fluid, generally air, by generating pressure fields at or close to the source of the aerodynamic noise, these pressure fields having amplitudes and frequencies equivalent to those of the noise fields to be reduced, but phases opposite thereto. These generated pressure fields globally cancel the effect of the noise fields and this affect is propagated into the far field. Use is made of planar electro-thermal transducers, transforming a periodically fluctuating heat flux generated by Joule AC heating into an acoustic wave. The frequency, amplitude and phase of the noise field may be detected by microphones positioned close to points of generation of the noise field, such that the cancellation is effective over the same region as the noise field propagates.

An apparatus, comprising a film (103) comprising a network of conductive and/or semi-conductive high aspect ratio molecular structures is presented. The apparatus also comprises a frame (102) arranged to support the film (103) at least at least two support positions so that a free-standing region (101) of the film (103) extends between the at least two support positions. The two or more electrical contact areas electrically coupled to the film (103), and these electrical contact areas are arranged to pass electric charge across the free-standing region (101) of the film (103) at a current between 0.01 and 10 amperes.

A thermoacoustic transducer apparatus is disclosed including at least one thermal converter operable to provide power conversion between acoustic power and thermal power in a pressurized working gas contained within a working volume, a portion of which extends through the thermal converter. The thermoacoustic transducer is operable to cause a periodic flow in the working gas during operation. The apparatus also includes a reservoir volume in fluid communication with the working volume through a conduit having a working volume end in fluid communication with the working volume and a reservoir volume end in fluid communication with the reservoir volume. The conduit has a bore size and length operable to cause pressure oscillations at the working volume end to be converted to flow oscillations at the reservoir volume end such that periodic fluid flow at the reservoir volume end is at least twice as large as periodic fluid flow at the working volume end thereby facilitating a steady fluid flow along the conduit for equalization of working gas static pressures between the working volume and the reservoir volume while providing a sufficiently high acoustic impedance at the working volume end to minimize losses due to periodic flows of working gas within the conduit.

A thermoacoustic device includes a waveguide with a loop shape, a heat exchanger, and a thermally conductive member. The waveguide with a loop shape is filled with a medium. The heat exchanger is provided in the waveguide and has a lower temperature part and a higher temperature part that produce a temperature gradient therebetween. The thermally conductive member changes a temperature of a central part of at least one of the lower temperature part and the higher temperature part.

A MEMS device includes a substrate having a cavity and a membrane structure mechanically connected to the substrate and configured for deflecting out-of-plane with regard to a substrate plane and with a frequency in an ultrasonic frequency range to cause a fluid motion of the fluid in the cavity. The MEMS device includes a valve structure sandwiching the cavity together with the membrane structure, wherein the valve structure includes a planar perforated structure and a shutter structure opposing the perforated structure and arranged movably in-plane and with a frequency in the ultrasonic frequency range and with regard to the substrate plane and between a first position and a second position. The shutter structure is arranged to provide a first fluidic resistance for the fluid in the first position and a second, higher fluidic resistance for the fluid in the second position.

A MEMS package comprises a first speaker arrangement configured for emitting sound in a first audio frequency range and a second speaker arrangement configured for emitting sound in a different second audio frequency range.

This disclosure provides systems, methods, and device associated with an electrostatically driven graphene speaker. In one aspect, the device includes a graphene membrane having a diameter of about 3 millimeters to about 11 millimeters, and a first electrode proximate a first side of the graphene membrane, the first electrode being electrically conductive. The device is a microphone or a loudspeaker.

A method of making a thermoacoustic device includes molding and cutting laminated sheets into half shell portions. Carbon nanotubes are adhered to a substrate having two electrical conducting portions thereon. Electrical conductors are applied to the conducting portions of the substrate. Tab sealant strips are applied around the perimeter of the substrate. Half shell portions are positioned on the top and bottom of the substrate with the electrical conductors extending therefrom. Heat is applied to seal the half shell portions together, suspending the substrate from the tab sealant strips. The method can further include providing a tube between the half shell portions prior to applying heat.

A thermal excitation acoustic-wave-generating device includes a first acoustic wave source that includes a first heating element and a substrate that includes a main surface along which the first heating element is disposed, a second acoustic wave source that includes a second heating element and a facing body that includes a main surface along which the second heating element is disposed, and a pair of electrodes connected to the first and second heating elements. The first and second acoustic wave sources are arranged such that the first and second heating elements are separated from each other and face each other. The pair of electrodes are disposed between the first and second acoustic wave sources.