Abstract: A noise-cancelling handset has reduced inter-user variability. The handset includes an earpiece housing. A space, referred to as the "front volume" is defined by the rear and side walls of this housing and a front surface containing acoustic ports for radiation of received sound into the user's ear. An error microphone is situated so as to sample the acoustic field within the front volume. In use, a further volume, referred to as the "forward volume," is defined between the front surface and the user's outer auditory canal. A leaky acoustic seal typically obtains between the front surface and the user's auditory canal. Thus, the forward volume will effectively have an acoustic leak, which has a characteristic, but variable acoustic impedance that is mostly of inductive character. At least one acoustic port is provided to effectuate a controlled leak to the outside of the handset.

Abstract: An improved, single diaphragm SOD microphone uses acoustic filters to remove resonances associated with the ducting that guides the ambient sound pressure to the front and rear faces of a FOD microphone element. The microphone element communicates with respective front and rear chambers, two ports communicate with the front chamber via front conduits, and two ports communicate with the rear chamber via rear conduits. The microphone further comprises first and second side chambers for dissipating acoustic energy of undesired resonances. The first side chamber communicates with the front conduits, and the second side chamber communicates with the rear conduits. In specific embodiments of the invention, each of the side chambers comprises a branch conduit approximately equal in length to one-quarter wavelength of an undesired resonance. In certain embodiments, each of these branch conduits includes a small neck joining the branch conduit to its corresponding front or rear conduits.