My wife is deaf in one ear; I mean almost completely. The only things she can hear in that ear would make normal people (or her other ear) go deaf. This has posed a problem on more than one occasion with our two kids. They will call out to her and it will take her a couple tries to figure out which room they are in. It is also interesting to call out to her in a store and watch her check every direction until she can see where I am calling from.
I was wondering if there was some way to help her work out directional hearing with a wearable device. A while back I was turned onto an anklet that would let you know which direction you were facing. It turns out that the human body will learn to filter out common sensations, such as vibration, over time while still intuitively sensing the changes in said vibration (a phenomenon well known in haptic devices). With this in mind I begun designing a device that will use a pair of microphone earrings to pass audio through a pair of op-amps that will power a pair of vibration motors, one on each arm in an armband worn under the clothes. This will allow, I hope, my wife to be able to determine the direction of sound. A schematic and parts list is forth-coming and a prototype will follow soon after.
Keep tuned-in for updates.