Methods and apparatus for a sound reducing mask wearable by a user according to various embodiments may include a body portion contoured to form a seal with the user’s face when the body portion is placed over the user’s mouth. The sound reducing mask may also include an air intake assembly including an inlet and a unidirectional flap configured to move between an open position and a closed position. Methods and apparatus for a sound reducing mask may further include a muffler configured to muffle noise made by the user.

The invention discloses a sound-absorbing material particle and a preparation method thereof. The method for preparing the sound-absorbing material particle comprises: mixing a sound-absorbing raw material with a solvent to form a sound-absorbing slurry; filling the sound-absorbing slurry into a mechanical compression die, and performing compression molding on the sound-absorbing slurry to form a particle; performing a hydrothermal crystallization reaction on the particle to crystallize the sound-absorbing raw material in the particle; and drying the particle to produce the sound-absorbing material particle.

The invention discloses a sound-absorbing material particle and a preparation method thereof. The method for preparing the sound-absorbing material particle comprises: mixing a sound-absorbing raw material with a solvent to form a sound-absorbing slurry; filling the sound-absorbing slurry into a mechanical compression die, and performing compression molding on the sound-absorbing slurry to form a particle; performing a hydrothermal crystallization reaction on the particle to crystallize the sound-absorbing raw material in the particle; and drying the particle to produce the sound-absorbing material particle.

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.

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.

Compact sound attenuation systems for fluid ducts are provided having one or more sound attenuation units that can be absorptive or reflective, depending on design. Each sound attenuation unit has one or more encircling Helmholtz resonators that fully encircle the duct in a lateral direction. Sound attenuation units can be coincident with the duct well and either interior or exterior to the duct, or in some instances can be partly interior and partly exterior to the duct. Sound attenuation systems can be tuned for maximum attenuation of a single resonance frequency, or can include multiple units of different frequencies for broadband attenuation.

Compact sound attenuation systems for fluid ducts are provided having one or more sound attenuation units that can be absorptive or reflective, depending on design. Each sound attenuation unit has one or more encircling Helmholtz resonators that fully encircle the duct in a lateral direction. Sound attenuation units can be coincident with the duct well and either interior or exterior to the duct, or in some instances can be partly interior and partly exterior to the duct. Sound attenuation systems can be tuned for maximum attenuation of a single resonance frequency, or can include multiple units of different frequencies for broadband attenuation.

A dual frequency ultrasound transducer includes a high frequency ultrasound array and a low frequency transducer positioned behind or proximal to the high frequency ultrasound array. In one embodiment, a dampening material is positioned between a rear surface of the high frequency array and the a front surface of the low frequency array. The dampening preferably is high absorbing of signals at the frequency of the high frequency array but passes signals at the frequency of the low frequency transducer with little attenuation. In additional, or alternatively, the low frequency can angled with respect to the plane of the high frequency transducer to reduce inter-stack multipath reflections. Beamforming delays compensate for the differences in physical distances between the elements of the low frequency transducer and the plane of the high frequency transducer.

A dual frequency ultrasound transducer includes a high frequency ultrasound array and a low frequency transducer positioned behind or proximal to the high frequency ultrasound array. In one embodiment, a dampening material is positioned between a rear surface of the high frequency array and the a front surface of the low frequency array. The dampening preferably is high absorbing of signals at the frequency of the high frequency array but passes signals at the frequency of the low frequency transducer with little attenuation. In additional, or alternatively, the low frequency can angled with respect to the plane of the high frequency transducer to reduce inter-stack multipath reflections. Beamforming delays compensate for the differences in physical distances between the elements of the low frequency transducer and the plane of the high frequency transducer.

Described herein are noise-resistant assemblies pursuant to various commercial and industrial applications. The noise-resistant assemblies can include duct assemblies, pool assemblies, motor assemblies, carpet flooring assemblies, and roofing assemblies. These assemblies incorporate an acoustic article containing a porous layer and a heterogeneous filler having a median particle size of from 1 micrometer to 1000 micrometers and a specific surface area of from 0.1 m.sup.2/g to 10,000 m.sup.2/g received in the porous layer.