A headphone ear cup holds the transducer. This patent focuses on applying tone wood porting theory to the headphone cup. Simply put, tone wood theory states that certain woods provide a tonality to the music. The practice of speaker porting has been in use for many years to extend the bass response of a speaker. By combining tone woods with porting, a more musical presentation created than by using a polymer or metal cup.

Electrical bonded portions (100, 104) from a coaxial cable (56) to a piezoelectric body (49) are bonded by a resin material having conductivity (102), and the electrical bonded portions (100, 104) using the resin material (102) are covered with a gas barrier epoxy resin layer (106).

An acoustic impedance matching device can facilitate acoustic transmission across an interface formed by materials having a very large acoustic impedance mismatch (e.g. air-water, or air-elastic polymer). The device can include a first medium. The first medium can have a first acoustic impedance. The device can include a second medium. The second medium can have a second acoustic impedance. The second acoustic impedance can be substantially greater than the first acoustic impedance. Thus, the first acoustic impedance and the second acoustic impedance are substantially mismatched. An interface can be defined between the first medium and the second medium. A bubble can be located in the second medium or the interface. The bubble can act as a resonator and can enable efficient sound transmission despite the large impedance mismatch of the first medium and the second medium.

A wild game call includes a bugle tube and a damper. The bugle tube includes a first end with a first aperture, a second end with a second aperture, and a wall extending from the first end to the second end. The wall defines an interior volume, and the first aperture and the second aperture provide access to the interior volume such that a flow path is defined through the bugle tube from the first end, through the second end, and out the second end. The bugle tube includes a metal and is configured to generate sound waves by vibrating responsive to air flowing along the flow path. The damper surrounds the outer surface of the wall of the bugle tube between the first end and the second end and may reduce unwanted ringing while improving the sound of the bugle call.

Proposed is an earplug that can effectively reduce high-frequency noise using a metasurface. The high-frequency noise filtering earplug using a metasurface according to an embodiment of the present disclosure may include an eartip with an internal passage, an interference attenuation module having a damping passage for reducing noise and a first reflective cavity that is connected to the damping passage and reflects incident sound waves and transmits the sound waves to the damping passage, and a connecting tube installed between the eartip and the interference attenuation module to connect the internal passage and the damping passage to each other.

An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.

A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.

A resonator (1, 1′, 1″) for reducing airborne noise has at least one first ring-shaped chamber (2, 2′, 2″) arranged between an inlet piece (6, 6′) and an outlet piece (7, 7′). An inner tube (3) or inner tube pieces (4, 4″, 5) are arranged between the inlet piece (6, 6′) and outlet piece (7, 7′) and have wall apertures (18, 19, 28, 28″, 29, 29″, 30, 30″) as a connection to the adjacent ring-shaped chamber (2, 2′, 2″). The first ring-shaped chamber (2, 2′, 2″) is divided by at least one radially encircling dividing rib (13, 13′, 13″) into at least two sub-chambers (14, 14′, 14″, 15, 15′, 15″). The dividing rib (13, 13′, 13″) has a free end that, relative to the wall that is adjacent in a radial direction, forms an encircling annular space (16) for receiving an air layer that co-resonates in steady-state.