| 摘要 |
Apparatus comprising: an earphone for an active noise reduction (ANR) earphone, comprising: structure for engaging an outer ear so that the earphone is positioned and retained in an ear of a user; a nozzle (70) providing a passageway that is adapted to acoustically seal the earphone with an ear canal (75) of the user at the transition between the bowl of a concha of the user and the entrance to the ear canal to form a cavity; ANR circuitry comprising a feedback microphone (11) adapted to be acoustically coupled to the ear canal, for detecting noise in the earphone; feedback circuitry (71) responsive to the feedback microphone for providing a feedback noise cancelling audio signal; and an acoustic driver (17) for transducing an output noise canceling audio signal comprising the feedback noise canceling audio signal to noise canceling acoustic energy ; the nozzle being oriented and shaped to control an acoustic impedance of the nozzle, such that at least one of: a cross sectional area of the nozzle, a ratio of the nozzle length to the nozzle cross sectional area, or an acoustic mass of the nozzle causes an absolute value of the acoustic impedance of the nozzle to be below 8 × 10 5 kg m 4 × sec at 100 Hz and below 8 × 10 6 kg m 4 × sec at 1 kHz. |
