The invention relates to a vibration damper (1) configured to be provided on a low frequency sound generator, which comprises a feeder unit (2) with a positive feedback system regulated by a reciprocating spring loaded piston (3) and a resonator tube (4). The vibration damper (1) may be positioned outside the resonator tube (4). The vibration damper (1) comprises a first flange (5) connected to the resonator tube (4), a number of springs (6), a second flange (7) and a number of weights (8).

The invention relates to a vibration damper (1) configured to be provided on a low frequency sound generator, which comprises a feeder unit (2) with a positive feedback system regulated by a reciprocating spring loaded piston (3) and a resonator tube (4). The vibration damper (1) may be positioned outside the resonator tube (4). The vibration damper (1) comprises a first flange (5) connected to the resonator tube (4), a number of springs (6), a second flange (7) and a number of weights (8).

An ultrasound transducer is provided. The ultrasound transducer include at least one emitter made from a piezoelectric material, having first and second emitting surfaces opposite one another provided to emit first and second ultrasound beams. The transducer comprises at least first and second mirrors placed across from the first and second emitting surfaces, respectively, and configured so as to deflect back the first and second ultrasound beams by forming a reflected beam with a predetermined shape.

A device includes a sound source, an electric board, an exterior member, an electric board container box, and a sound absorber. The sound source generates a sound at a time of operation. The electric board has a circuit mounting an electrical component. The exterior member surrounds the sound source and the electric board. The electric board container box houses the electric board. The sound absorber is at least partially disposed inside a virtual space corresponding to a thickness of the electric board container box in an interior space of the device.

The anisotropic media has an anisotropic layer, is disposed between outer isotropic media, causes multiple mode transmission on an elastic wave having a predetermined mode incident into the anisotropic media, and has a mode-coupling stiffness constant not zero. A thickness of the anisotropic layer according to modulus of elasticity and excitation frequency satisfies Equation (2) which is a phase matching condition of elastic waves propagating along the same direction or Equation (3) which is a phase matching condition of elastic waves propagating along the opposite direction, to generate mode conversion Fabry-Pérot resonance,
Δϕ≡k.sub.qld−k.sub.qsd=(2n+1)π,   Equation (2)
Σϕ≡k.sub.qld+k.sub.qsd=(2m+1)π,   Equation (3) k.sub.ql is wave numbers of anisotropic media with quasi-longitudinal mode. l.sub.qs is wave numbers of anisotropic media with quasi-shear mode. d is a thickness of anisotropic media. n and m are integers.

The anisotropic media has an anisotropic layer, is disposed between outer isotropic media, causes multiple mode transmission on an elastic wave having a predetermined mode incident into the anisotropic media, and has a mode-coupling stiffness constant not zero. A thickness of the anisotropic layer according to modulus of elasticity and excitation frequency satisfies Equation (2) which is a phase matching condition of elastic waves propagating along the same direction or Equation (3) which is a phase matching condition of elastic waves propagating along the opposite direction, to generate mode conversion Fabry-Pérot resonance,
Δϕ≡k.sub.qld−k.sub.qsd=(2n+1)π,   Equation (2)
Σϕ≡k.sub.qld+k.sub.qsd=(2m+1)π,   Equation (3) k.sub.ql is wave numbers of anisotropic media with quasi-longitudinal mode. l.sub.qs is wave numbers of anisotropic media with quasi-shear mode. d is a thickness of anisotropic media. n and m are integers.

A partially or mainly enclosed passive apparatus, inclusive of a method and system to be used with input sounds, possibly vocals or voice, to alter and yield different and various effects to the sound being input. The passive apparatus is comprised of an exterior shell and removable enclosure structure, both of a shape, contour, and dimensions to be effective in containing a level of sound being input. Additionally, the apparatus may employ a variety of permanent, removable, relocatable solid shapes to yield desired effects of the user.

A movable, hollow cubical housing for enhancing the sound output of a mobile, wireless speaker. A plurality of apertures being provided in the side walls of the housing. The housing being provided with sound dampening material on the interior of the housing.

Disclosed herein are systems using acoustic metamaterial surfaces comprising arrangements of unit cells arranged to introduce time delays to an incident acoustic wave. In embodiments the relative positions of two or more acoustic metasurfaces (81, 82) is selected or adjusted to control the acoustic output of the system such that the acoustic output of the system is a non-linear combination of the respective operations performed by the plurality of acoustic metasurfaces (81, 82), the non-linear combination being a convolution of the respective operations performed by the plurality of acoustic metasurfaces that is determined as a function of the relative positioning between the acoustic metasurfaces (81, 82). Also disclosed are applications of such acoustic metasurfaces in noise-reducing structures.

An embodiment of the present invention provides an ultrasonic wave amplifying unit which can improve ultrasonic power in air, wherein the ultrasonic wave amplifying unit includes multiple rings having a concentric axis and each having a first width, and a slit having a second width is formed between the rings and an air layer is formed between the multiple rings and an ultrasonic wave generator generating ultrasonic waves or a transfer medium transferring the ultrasonic waves.