It's nice to roll two strangely similar IotDs together like this.
This hearing aid is actually implanted into the skin of the guy wearing it. With this device, the person "hears" the sound as normal, but different frequencies are amplified, so that people with hearing losses in certain frequencies can get a louder blast of them.
The idea seems to be to make the device less intrusive so that you forget it's even there. The opposite of ear horns.
This is a benefit to those of us born after the baby boomers: they solve problems like this for us before we need them.
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