Acoustic conversion device for active noise control
View Patent ↗An acoustic conversion device for an active noise control is provided. The acoustic conversion device can effectively suppress or remove noise by controlling variation in a lowest resonance frequency. A volume of a closed space is smaller than an equivalent compliance air volume of a speaker unit. Therefore, motion of a vibration plate, an edge and a damper is suppressed, it is possible to restrain the edge and the damper from being deteriorated with time, variation in lowest resonance frequency can be suppressed, phase of emitted sound can be less prone to be deviated from opposite phase of noise, and it is possible to effectively suppress or remove noise.
1. An acoustic conversion device for an active noise control comprising:
a speaker unit for emitting sound into a room space of a vehicle; and
a closed space-forming unit for forming a closed space, the speaker unit being mounted to the closed space-forming unit, wherein
the speaker unit includes a vibration plate and an edge which supports the vibration plate, one surface of the vibration plate emits sound to the room space, and the other surface thereof emits sound to the closed space,
a volume of the closed space is smaller than an equivalent compliance air volume of the speaker unit,
an effective vibration diameter of the vibration plate is 10 cm or more and 14 cm or less, and
the volume of the closed space is 5 liters or more and 7 liters or less.
2. The acoustic conversion device for the active noise control according to claim 1 , wherein the volume of the closed space is 40% or more and 80% or less of the equivalent compliance air volume.
3. The acoustic conversion device for the active noise control according to claim 1 , wherein a lowest resonance frequency in a state where the speaker unit and the closed space-forming unit are assembled together is 30 Hz or more and 50 Hz or less.
4. The acoustic conversion device for the active noise control according to claim 1 , wherein the closed space-forming unit is provided below a seat of the vehicle.
5. The acoustic conversion device for the active noise control according to claim 1 , wherein the closed space-forming unit is provided in a dashboard of the vehicle.
6. The acoustic conversion device for the active noise control according to claim 1 , wherein the closed space-forming unit is provided under a floor of the vehicle.
7. The acoustic conversion device for the active noise control according to claim 1 , wherein the closed space-forming unit includes a first member forming a first closed space in which the speaker unit is accommodated, and a second member forming a second closed space which is in communication with the first closed space, and
wherein sound emitted from the speaker unit to the first closed space is emitted to the second closed space.
8. The acoustic conversion device for the active noise control according to claim 1 , wherein the closed space-forming unit includes a first member forming a first closed space in which the speaker unit is accommodated, and a second member forming a second closed space which is in communication with the first closed space, and
wherein the volume of the closed space is a total of a volume of the first closed space and a volume of the second closed space.