Acoustic resonance device

Abstract

An acoustic resonance device is installed in a compartment of a vehicle so as to reduce a low-frequency sound pressure (or noise) dependent upon a natural vibration. Specifically, an acoustic resonance device is a panel / diaphragm resonator, a resonance pipe, or a Helmholtz resonator, the inner space of which communicates with the compartment via an opening. The acoustic resonance device is positioned in proximity to an antinode of sound pressure owing to a natural vibration occurring in a driver / passenger space inside the compartment. Alternatively, the acoustic resonance device increases a particle velocity at a specific natural frequency or decreases sound pressure at an excitation frequency which occurs due to an external condition of the vehicle. The acoustic resonance device can be installed in a roof, a seat, a pillar supporting the roof, or a door of a vehicle.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to acoustic resonance devices which reduce sounds / noises in cabins / compartments of vehicles.[0003]The present application claims priority on Japanese Patent Application No. 2009-206496, the content of which is incorporated herein by reference.[0004]2. Description of the Related Art[0005]Conventionally, various technologies have been developed to improve quietness / noiselessness in cabins / compartments of vehicles by use of sound-absorbing materials. Patent Document 1 discloses a sound-absorbing material (e.g. a felt material) attached to a duct inside a dash panel in a cabin of a vehicle. Patent Document 2 discloses a panel / diaphragm sound-absorbing structure in which a panel / diaphragm vibrator and a rear cavity (or an air space in the rear of the vibrator) cooperate together to absorb sound.[0006]Even when the technology of Patent Document 1 adopts the sound-absorbing structure of Patent Doc...

AI Technical Summary

Benefits of technology

[0009]It is an object of the present invention to provide an acoustic resonance device which reduces low-frequency sound so as to demonstrate a sound-absorbing effect at positions of seats at which a driver and / or passengers actually hear sound / noise inside a vehicle.

[0010]An acoustic resonance device according to the present invention is installed in a compartment of a vehicle and constituted of at least one resonator having an inner space and an opening. The resonator is arranged in the compartment of a vehicle such that the inner space communicates with the compartment via the opening. The resonator reduces sound pressure at a specific natural frequency corresponding to an antinode of a natural vibration emerging in a driver / passenger space inside the compartment of a vehicle.

[0013]Furthermore, the resonator reduces sound pressure at an excitation frequency which occurs due to an external condition of the vehicle and which differs from the specific natural frequency.

[0016]Generally speaking, a low-frequency sound which a driver / passenger may distinctively sense as noise has a strong dependency on a natural vibration occurring in the compartment of a vehicle. Considering a natural vibration which occurs in a height equivalent to the position of a driver / passenger's head on a front seat, the wavelength is approximately twice the width of a vehicle so that sound pressure spreads in the width direction of a vehicle. Antinodes of sound pressure owing to this natural vibration emerge in proximity to side windows fixed above front doors of a vehicle. For this reason, an acoustic resonance device is positioned to reduce sound pressure or to increase particle velocity at an antinode of sound pressure which is closest to the driver / passenger space among a plurality of antinodes of sound pressure owing to a natural vibration, thus achieving mode suppression. That is, the present invention is able to reduce a low-frequency sound pressure and to thereby improve a noise reduction effect at a driver / passenger's position at which a driver / passenger actually suffers from noise.

Problems solved by technology

Even when the technology of Patent Document 1 adopts the sound-absorbing structure of Patent Document 2, it is difficult to sufficiently reduce low-frequency sound owing to engine sound of a vehicle and frictional noise (which occurs due to friction between tires and roads while a vehicle is running).

The technology of Patent Document 1 is unable to demonstrate a high sound-absorbing effect at positions of seats at which a driver and / or passengers may actually hear sound / noise inside a vehicle.

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