Described are methods and systems for broad-band active reduction of noise in target spaces, such as spaces around headrests in aircraft cabins. Systems describe herein are effective over wide frequency ranges without causing undesirable amplification at any subrange ranges. Specifically, a system comprises a speaker and a resonator, both coupled to an enclosure. The interior space of the resonator is in fluid communication with the enclosed space of the enclosure, allowing the resonator to reduce the amplitude of unwanted amplification by the audio reducing sound generated by the speaker. The amplitude is reduced in a selected frequency range, which may correspond to an expected amplification for this particular system. The resonator may partially extend into the enclosure or may be completely incorporated into the enclosure. Some examples of the resonator include a Helmholtz resonator, a passive radiator, a quarter wave resonator, a pipe resonator, and an acoustic metamaterial.

A vehicle exhaust component includes a body with an open inner cavity providing a fixed volume and a neck having one end associated with the fixed volume and an opposite end associated with an exhaust gas flow path. A flexible membrane separates the fixed volume into a first chamber and a second chamber. An actuator is used to vary a tension of the flexible membrane.

Described are methods and systems for broad-band active reduction of noise in target spaces, such as spaces around headrests in aircraft cabins. Systems describe herein are effective over wide frequency ranges without causing undesirable amplification at any subrange ranges. Specifically, a system comprises a speaker and a resonator, both coupled to an enclosure. The interior space of the resonator is in fluid communication with the enclosed space of the enclosure, allowing the resonator to reduce the amplitude of unwanted amplification by the audio reducing sound generated by the speaker. The amplitude is reduced in a selected frequency range, which may correspond to an expected amplification for this particular system. The resonator may partially extend into the enclosure or may be completely incorporated into the enclosure. Some examples of the resonator include a Helmholtz resonator, a passive radiator, a quarter wave resonator, a pipe resonator, and an acoustic metamaterial.

An image forming apparatus includes a cartridge unit and a cartridge support member. The cartridge unit includes a photosensitive drum on a surface of which an electrostatic latent image is to be formed. The cartridge support member supports the cartridge unit inside an apparatus main body. The cartridge unit is detachable from the apparatus main body. In a case where the cartridge unit is attached to the apparatus main body, a Helmholtz resonator including a communication portion and including a cavity portion is constituted of the cartridge unit and the cartridge support member. The cartridge unit includes at least a part of the communication portion of the Helmholtz resonator.

In a vehicle wheel including a rim, a sub-air chamber member serving as a Helmholtz resonator, and a tire pressure sensor unit, the sub-air chamber member and the tire pressure sensor unit are integrated with each other to be mounted on the rim via an air valve. The tire pressure sensor unit is preferably integrated with the air valve. The vehicle wheel may be configured such that the sub-air chamber member is connected to the tire pressure sensor unit via a bracket, and the bracket is insert-molded in the sub-air chamber member. Moreover, an edge of the sub-air chamber member may be locked to a well part at an opposite side in a wheel width direction to the tire pressure sensor unit.

In a vehicle wheel including a sub-air chamber member serving as a Helmholtz resonator, the sub-air chamber member is disposed in a tire air chamber with being supported by an air valve. The sub-air chamber member is connected to the air valve via a bracket, and the bracket is insert-molded in the sub-air chamber member. Alternatively, the sub-air chamber member is supported by the air valve via a support member. In this structure, the support member supports the sub-air chamber member so as to surround circumference of the sub-air chamber member, or has a gripping part nearly of a channel shape that grips the sub-air chamber member.

Provided is a vehicle wheel with a sub-air chamber member as a Helmholtz resonator attached to a rim. The sub-air chamber member includes a main body having a sub-air chamber therein, a tubular body providing communication between the sub-air chamber and a tire air chamber, and a cover member covering the main body. The main body is disposed on a rim inner circumferential surface portion of the rim present on an inner side of the rim in a wheel radial direction and extending in a wheel width direction. The tubular body is disposed in a through-hole provided in the rim so as to provide communication between the inner side of the rim in the wheel radial direction and the tire air chamber side. The cover member covers the main body from an inner side in the wheel radial direction.

Sound absorbers using distributed absorption units each having an extended neck are provided. The absorption units can be, for example, Helmholtz resonators with extended neck (HRENs). The absorption units can be distributed in a lateral fashion, for example, in a checkerboard fashion with laterally, non-diagonally adjacent units having a different extended neck length and/or diameter. Each absorption unit can be, for example, a cylinder-structure core sandwiched between a back wall and a perforated plate.

Described are methods and systems for broad-band active reduction of noise in target spaces, such as spaces around headrests in aircraft cabins. Systems describe herein are effective over wide frequency ranges without causing undesirable amplification at any subrange ranges. Specifically, a system comprises a speaker and a resonator, both coupled to an enclosure. The interior space of the resonator is in fluid communication with the enclosed space of the enclosure, allowing the resonator to reduce the amplitude of unwanted amplification by the audio reducing sound generated by the speaker. The amplitude is reduced in a selected frequency range, which may correspond to an expected amplification for this particular system. The resonator may partially extend into the enclosure or may be completely incorporated into the enclosure. Some examples of the resonator include a Helmholtz resonator, a passive radiator, a quarter wave resonator, a pipe resonator, and an acoustic metamaterial.

A method of using an acoustic resonator including receiving at a first stage of a resonator an incoming acoustic wave. The method further includes resonating the incoming wave with a flexible membrane, a taper of the flexible membrane, and a cavity of a first stage, thereby producing synergistic effect on a resulting acoustic resonance. Additionally, the method includes transforming an acoustic energy associated with the incoming acoustic wave into an elastic energy, wherein the elastic energy is channeled through the flexible membrane, thereby reducing an intensity of the incoming acoustic wave and resulting in a first reduced incoming acoustic wave. Further the method includes transferring the first reduced incoming acoustic wave through a hole of a neck of the flexible membrane. The method also includes transferring a first pressure wave caused by a perturbation in the flexible membrane into a second stage, thereby producing a second acoustic wave.