An acoustic absorber includes a chamber formed from walls with a resistive portion providing the only communication between the chamber volume and ambient air. In some examples chamber walls enable selection or adjustment of chamber volume or resistive area, thereby altering the acoustic absorption spectrum below 250 Hz. In some examples the chamber volume contains fibrous filler material exhibiting no airflow resistance or acoustic absorption. Density and heat capacity of the fibrous filler material results in the chamber volume exhibiting compressibility of air within the chamber, for at least acoustic frequencies up to about 50 Hz, that is larger than adiabatic compressibility of air. That larger compressibility results in an increased acoustic absorption coefficient, for at least acoustic frequencies up to about 50 Hz, 50% to 100% larger than that of an identical chamber entirely characterized by the adiabatic compressibility of air.

An acoustic metamaterial (AMM) passive impedance matching device for headphone-type devices for matching the complex acoustic impedance load of a human ear to enhance acoustic performance of a headphone is disclosed. The device includes shunt compliance chambers stacked concentrically relative to one another from an upper end to a lower end. Each of the shunt compliance chambers includes side connecting inductive channels positioned annularly around a circumference of at least one of the shunt compliance chambers. The shunt compliance chambers define a predetermined volume of air. The inductive channels connect the shunt compliance chambers to the main headphone volume, generating an acoustic resistance and reactive impedance that matches the complex acoustic impedance load of the human ear canal. The AMM device also includes an inductive channel, as a design parameter, extending from the main headphone volume to the ambient air serving as an additional resistive and reactive load.

An acoustic metamaterial (AMM) passive impedance matching device for headphone-type devices for matching the complex acoustic impedance load of a human ear to enhance acoustic performance of a headphone is disclosed. The device includes shunt compliance chambers stacked concentrically relative to one another from an upper end to a lower end. Each of the shunt compliance chambers includes side connecting inductive channels positioned annularly around a circumference of at least one of the shunt compliance chambers. The shunt compliance chambers define a predetermined volume of air. The inductive channels connect the shunt compliance chambers to the main headphone volume, generating an acoustic resistance and reactive impedance that matches the complex acoustic impedance load of the human ear canal. The AMM device also includes an inductive channel, as a design parameter, extending from the main headphone volume to the ambient air serving as an additional resistive and reactive load.

According to one embodiment, a sound absorption device includes: a first plate having a plurality of first holes; a second plate facing the first plate in a first direction; a first frame connecting the first plate and the second plate; and a third plate supported by the first frame so as to vibrate in the first direction within the first frame. A first space is formed in the first frame between the first plate and the third plate. A second space is formed in the first frame between the second plate and the third plate. The third plate includes a first portion and a second portion, the second portion having a higher vibration speed than the first portion.

Embodiments of this application disclose a noise reduction headset. A branch pipe is disposed in the headset to connect a sound cavity inside the headset and an external environment. The branch pipe has a low-pass filter function to filter out high-band noise entering the sound cavity from the external environment, so that impact on sound quality inside the sound cavity that is caused by noise in the external environment is reduced, thereby implementing passive noise reduction.

A noise-cancelling earplug assembly is provided, having an ear piece for insertion into the ear canal and a housing removably attached to the ear piece. A hollow core is defined in the housing to receive a sound-selective sound barrier that contains at least one sound filtering element to attenuate sounds reaching the ear drum. An end cap is provided and is attachable to the housing to enclose the sound-selective sound barrier inside the housing. The sound selective sound barrier can be removed from the housing of the earplug and replaced with a different sound selective sound barrier with different sound attenuation characteristics.

A noise-cancelling earplug assembly is provided, having an ear piece for insertion into the ear canal and a housing removably attached to the ear piece. A hollow core is defined in the housing to receive a sound-selective sound barrier that contains at least one sound filtering element to attenuate sounds reaching the ear drum. An end cap is provided and is attachable to the housing to enclose the sound-selective sound barrier inside the housing. The sound selective sound barrier can be removed from the housing of the earplug and replaced with a different sound selective sound barrier with different sound attenuation characteristics.

A vibration reducing device is attached to a structure and blocks sound transmitted through the structure. The vibration reducing device includes a unit structure having a target frequency band, the unit structure including a plurality of unit cells, each formed of an acoustic meta-material and having a different target frequency, the unit cells being connected through first bridges; and a predetermined number of unit structures being connected through second bridges and attached to the structure, where each of the unit cells comprises: a mass portion of which a size is set according to the target frequency; a base frame formed as a quadrangular frame, the mass portion being eccentrically disposed in the base frame; and a support portion that connects the mass portion and the base frame, the support portion having a size that is set according to the target frequency.

The present invention relates to a noise reduction assembly for auscultation of a body. An embodiment of the assembly includes an auscultation device formed of a first material and having a proximal end for engagement with the body when the auscultation device is in an operative orientation. An interior dampening layer, which may be formed of a second material, is formed along an exterior surface of the auscultation device and covering all exterior surfaces thereof except the proximal end. An exterior dampening layer, which may be formed of a third material, is then formed in covering relations relative to the interior dampening layer.

The present invention relates to a noise reduction assembly for auscultation of a body. An embodiment of the assembly includes an auscultation device formed of a first material and having a proximal end for engagement with the body when the auscultation device is in an operative orientation. An interior dampening layer, which may be formed of a second material, is formed along an exterior surface of the auscultation device and covering all exterior surfaces thereof except the proximal end. An exterior dampening layer, which may be formed of a third material, is then formed in covering relations relative to the interior dampening layer.