Earphone having acoustic impedance branch for damped ear canal resonance and acoustic signal coupling

An acoustic noise reduction earphone comprising:

• an earphone assembly having an earphone body with an inner surface and an external surface, an acoustic opening and a cavity defined by the inner surface and the acoustic opening, the earphone assembly further including a first acoustic impedance branch extending from an open end at the inner surface to a closed end inside the earphone body, wherein the first acoustic impedance branch includes a branch volume that reduces a magnitude of a resonance at a first resonance frequency for an occluded ear canal defined by the cavity of the earphone assembly and an ear canal of a user when the earphone is at least partially inserted into the ear canal;
• a first electro-acoustic transducer disposed inside the earphone assembly and configured to generate a first acoustic signal in response to a first electrical signal;
• a second electro-acoustic transducer disposed inside the earphone body along a length of the acoustic impedance branch and configured to generate a second acoustic signal in response to a second electrical signal;
• at least one of a feedforward microphone disposed on the external surface of the earphone body and configured to generate a feedforward electrical signal in response to an external acoustic signal and a feedback microphone disposed in the cavity and configured to generate a feedback electrical signal in response to a cavity acoustic signal;
• and
• a circuit in electrical communication with the first and second electro-acoustic transducers and the at least one of a feedforward microphone and feedback microphone, the circuit generating the first and second electrical signals received by the first and second electro-acoustic transducers, respectively, in response to the at least one of the feedback electrical signal and the feedforward electrical signal.

An earphone comprising:

• an earphone assembly having an earphone body with an inner surface, an acoustic opening and a cavity defined by the inner surface and the acoustic opening, the earphone assembly further including a waveguide having a length equal to one quarter of an acoustic wavelength for the first resonance frequency and extending from an open end at the inner surface to a closed end inside the earphone body, wherein the waveguide reduces a magnitude of a resonance at a first resonance frequency for an occluded ear canal defined by the cavity of the earphone assembly and an ear canal of a user when the earphone is at least partially inserted into the ear canal;
• a first electro-acoustic transducer disposed in the earphone assembly and configured to generate a first acoustic signal in response to a first electrical signal;
• and
• a second electro-acoustic transducer disposed in the earphone body along a length of the waveguide and configured to generate a second acoustic signal in response to a second electrical signal.