Nearly 28 million Americans have some type of hearing loss, according to the National Institutes of Health. And among older adults, hearing loss is the third most common chronic condition. It's therefore no surprise that the global hearing-aid industry tops $2 billion, according to investment firm US Bancorp Piper Jaffray. Advances in hearing-aid technology have led to chip-based digital sound-processing devices that are smaller, easier to customize, and more effective than analog hearing aids. Also showing promise are cochlear implants, surgically implanted devices that help restore hearing by electronically stimulating nerves in the ear. Although the procedure is still relatively new and a few cases have led to meningitis, overall, cochlear implants have shown initial success in restoring hearing to the deaf and severely hearing impaired. Long-term promise lies in research in nerve regeneration and the electrical workings of the auditory system.