ACOUSTIC SIGNAL OUTPUT DEVICE
Provided is an acoustic signal output device including a first driver unit that emits a first acoustic signal to one side and emits a second acoustic signal to another side, a second driver unit that emits a fourth acoustic signal to one side and emits a third acoustic signal to another side, a first housing portion provided with a first sound hole for leading out the first acoustic signal to an outside and a second sound hole for leading out the second acoustic signal to an outside, and a second housing portion provided with a third sound hole for leading out the third acoustic signal to an outside and a fourth sound hole for leading out the fourth acoustic signal to an outside. Provided that a frequency bandwidth of the third and fourth acoustic signals emitted from the second driver unit is narrower than a frequency bandwidth of the first and second acoustic signals emitted from the first driver unit.
1 . An acoustic signal output device comprising:
a first driver unit that emits a first acoustic signal to one side and emits a second acoustic signal to another side;
a second driver unit that emits a fourth acoustic signal to one side and emits a third acoustic signal to another side;
a first housing portion in which a wall portion is provided with a single or plurality of first sound holes for leading out the first acoustic signal emitted from the first driver unit to an outside and a single or plurality of second sound holes for leading out the second acoustic signal emitted from the first driver unit to an outside; and
a second housing portion in which a wall portion is provided with a single or plurality of third sound holes for leading out the third acoustic signal emitted from the second driver unit to an outside and a single or plurality of fourth sound holes for leading out the fourth acoustic signal emitted from the second driver unit to an outside,
wherein a frequency bandwidth of the third acoustic signal and the fourth acoustic signal emitted from the second driver unit is narrower than a frequency bandwidth of the first acoustic signal and the second acoustic signal emitted from the first driver unit,
in a case where the first acoustic signal is emitted from the first sound holes, the second acoustic signal is emitted from the second sound holes, the third acoustic signal is emitted from the third sound holes, and the fourth acoustic signal is emitted from the fourth sound holes, an attenuation rate of the first acoustic signal at a second point with reference to a predetermined first point, where the first acoustic signal arrives at the first point and the second point is farther from the acoustic signal output device than the first point, is designed to be equal to or less than a predetermined value smaller than an attenuation rate due to air propagation of an acoustic signal at the second point with reference to the first point, or an attenuation amount of the first acoustic signal at the second point with reference to the first point is designed to be equal to or more than a predetermined value larger than an attenuation amount due to air propagation of an acoustic signal at the second point with reference to the first point.
2 . The acoustic signal output device according to claim 1 ,
wherein magnitude of a component of a first frequency or higher of the third acoustic signal and the fourth acoustic signal emitted from the second driver unit is smaller than magnitude of a component of the first frequency or higher of the first acoustic signal and the second acoustic signal emitted from the first driver unit.
3 . The acoustic signal output device according to claim 1 ,
wherein magnitude of a component of a second frequency or lower of the third acoustic signal and the fourth acoustic signal emitted from the second driver unit is smaller than magnitude of a component of the second frequency or lower of the first acoustic signal and the second acoustic signal emitted from the first driver unit.
4 . The acoustic signal output device according to claim 1 ,
wherein the first sound holes open in a first direction,
the second sound holes open in a second direction between the first direction and a direction opposite to the first direction,
the fourth sound holes open in a fourth direction that is same as or approximate to the first direction, and
the third sound holes open in a third direction between the fourth direction and a direction opposite to the fourth direction.
5 . The acoustic signal output device according to claim 4 ,
wherein the first sound holes and the fourth sound holes are plane-symmetric or substantially plane-symmetric with respect to a reference plane including a straight line parallel or substantially parallel to a straight line extending in the first direction, and the second sound holes and the third sound holes are plane-symmetric or substantially plane-symmetric with respect to the reference plane.
6 . The acoustic signal output device according to claim 5 ,
wherein the first housing portion and the second housing portion are plane-symmetric or substantially plane-symmetric with respect to the reference plane.
7 . The acoustic signal output device according to claim 4 ,
wherein a plurality of the second sound holes is provided along a first circumference centered on a first axis parallel or substantially parallel to a straight line extending in the first direction, and
a plurality of the third sound holes is provided along a fourth circumference centered on a fourth axis parallel or substantially parallel to a straight line extending in the fourth direction.
8 . The acoustic signal output device according to claim 7 ,
wherein, in a case where the first circumference is equally divided into a plurality of first unit arc regions, a sum of an opening area of the second sound holes provided along a first arc region that is one of the first unit arc regions is same as or substantially same as a sum of an opening area of the second sound holes provided along a second arc region that is one of the first unit arc regions excluding the first arc region, and
in a case where the fourth circumference is equally divided into a plurality of fourth unit arc regions, a sum of an opening area of the third sound holes provided along a third arc region that is one of the fourth unit arc regions is same as or substantially same as a sum of an opening area of the third sound holes provided along a fourth arc region that is one of the fourth unit arc regions excluding the third arc region.
9 . The acoustic signal output device according to claim 7 ,
wherein a position of the first sound holes is biased to a first eccentric position deviated from a first center axis extending in the first direction through a center region of the first housing portion,
in a case where the first circumference is equally divided into a plurality of first unit arc regions, a sum of an opening area of the second sound holes provided along a first arc region that is one of the first unit arc regions is smaller than a sum of an opening area of the second sound holes provided along a second arc region that is one of the first unit arc regions closer to the first eccentric position than the first arc region,
a position of the fourth sound holes is biased to a fourth eccentric position deviated from a second center axis extending in the fourth direction through a center region of the second housing portion, and
in a case where the fourth circumference is equally divided into a plurality of second unit arc regions, a sum of an opening area of the fourth sound holes provided along a third arc region that is one of the second unit arc regions is smaller than a sum of an opening area of the fourth sound holes provided along a fourth arc region that is one of the second unit arc regions closer to the fourth eccentric position than the third arc region.
10 . The acoustic signal output device according to claim 1 ,
wherein the first sound holes are arranged in a direction of an ear canal, and the second sound holes, the third sound holes, and the fourth sound holes are arranged in a direction of other than the ear canal when the acoustic signal output device is worn on an ear.