US Patent 9621973 Wearable audio device

In one embodiment, a device includes at least one transducer configured to vibrate within a first frequency range to generate a signal audible by a wearer of the device. The device includes the first material, which has an acoustic impedance at one or more frequencies within the first frequency range that is substantially similar to an acoustic impedance of the wearer's skin at the one or more frequencies. The device includes a second material that has an acoustic impedance at one or more frequencies within the first frequency range that substantially differs from an acoustic impedance of an environment of the device.