| 摘要 |
An ear-worn speaker carrying device ("ESD") such as a headset or earphones incorporates feedforward active ambient noise reduction circuitry. A seal 36 contacts or surrounds the ear of a user and is intended to present a substantial impedance to inward or outward transmission of sound to or from the ear. At least one acoustic channel 42 of predetermined dimensions bypasses the seal to providing an acoustic leakage path of known characteristics, thereby permitting predetermined levels of sound to enter and exit by way of the channel, such that minor variations in leakage, dependent, for example, upon precise mounting of the seal to the ear become relatively unimportant. The device further comprises a further acoustic conduit 54 connected to vent the speaker's rear surface to the external ambient, and respective exit apertures for the acoustic channel and the acoustic conduit are so relatively located that sounds exiting from them tend to cancel each other, reducing sound emissions from the device. Each of the channels 42, 54 may be damped (fig 5). |
