Acoustic output devices

An acoustic output device comprising:

• at least one acoustic driver;
• a first cavity and a second cavity acoustically coupled to opposite sides of the at least one acoustic driver, respectively, the first cavity being provided with a first acoustic hole, the second cavity being provided with a second acoustic hole, and the at least one acoustic driver radiating sounds with a phase difference to an outside environment through the first acoustic hole and the second acoustic hole, wherein
• within a target frequency band, the sound radiated by the acoustic output device to a far-field has directivity, which is manifested in that the sounds radiated from the first acoustic hole and the second acoustic hole have a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and
• a difference between acoustic loads of the first acoustic hole and the second acoustic hole is less than 0.15.

An acoustic output device comprising:

• at least one acoustic driver;
• a first cavity and a second cavity acoustically coupled to opposite sides of the at least one acoustic driver, respectively, the first cavity being provided with a first acoustic hole, the second cavity being provided with a second acoustic hole, and the at least one acoustic driver radiating sounds with a phase difference to an outside environment through the first acoustic hole and the second acoustic hole, wherein
• within a target frequency band, the sound radiated by the acoustic output device to a far-field has directivity, which is manifested in that the sounds radiated from the first acoustic hole and the second acoustic hole have a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and
• a ratio of surface acoustic loads of the first acoustic hole and the second acoustic hole is in a range of 0.5-3.5.