Winning the War Against Hearing Loss: Why It Took So Long

Part 2 in a series

Technology impacts everyday life. Last year while driving home after skiing at Mammoth we got caught in a blinding snowstorm. It was night. Visibility was zero. I could not see the road. I had no way of knowing when to turn to get back to our lodge.

Fortunately, we had a new GPS unit that guided us home. “Turn right in 200 feet. Turn right in 100 feet. Turn right in 50 feet. Turn right now!” As I turned the car, I laughed and told my passengers, “We might be going down the side of a mountain.” I never saw the road until I made the turn.

Wonderful improvements in technology show up in all professions. In these 10 articles on “Winning the War Against Hearing Loss,” I am going to argue that the field of hearing aids is changing as fast, if not faster, than any other. Those of us who are fitting hearing aids today are lucky. We are working at the right place at the right time.

These major improvements did not come out of a void. Technology has been developing for years. A lot of useful, down-to-earth science was understood in the 1950s and 60s, but we did not see these concepts begin to be integrated into hearing aids until the final decades of the 20th century. Why not? And why are we seeing that happen now?

 

REASONS FOR THE DELAY

The reasons are simple: The military knew about background noise cancellation 60 years ago. Scientists had learned how to eliminate more than 90 dB of same-frequency noise from a “signal jammer” dropped in the water near a submarine. The computer that was used to perform this task—eliminate noise in warfare—was the size of a refrigerator and cost several million dollars. Today, greater processing capacity is built into inexpensive computer chips that are smaller than a pea.

It also took 60 years to make tiny microphone arrays (a quarter the size of a pea). The microphones used in the arrays on the old submarines were large and scattered all over the vessel. Only recently have the technologies of signal-detection and microphone-array systems been incorporated into hearing aids.

Bell Labs knew a lot about speech intelligibility 60 years ago. They designed communications systems that sent easy-to-understand speech signals to the moon. The phone companies were successful because speech scientists had worked out the “information science” of word understanding and standardized the concept of a “speech cue.”

Real-ear testing was also conducted decades ago. But only recently have we learned how to deliver audio signals to the human ear and maximize speech intelligibility under all listening conditions.

It took 60 years to digitize the human voice, to digitally recognize the difference between the human voice and background noise, and to deliver speech information efficiently to the ear. Now, this technology can deliver unbelievable results in a noisy coffee shop.

The recording industry created “high fidelity” many years ago. Back then, wide-band, distortion-free sound systems were created using bass, mid-range, and tweeter speakers driven by mega-powerful amplifiers. The speaker cabinets were larger than microwave ovens. Today we create this quality of sound with a unit the size of a pea—assuming we pay careful attention to real-ear mechanics.

The principles of FM and AM transmission were also understood 60 years ago. Some classrooms for hard-of-hearing children were equipped with complex, expensive FM equipment. However, it took many years to invent Bluetooth technology that made it possible to provide affordable signal-transmission systems for hearing aids.

The principle of feedback cancellation was also known in the 1950s. Here again it took decades to incorporate digital, phase inversion, and feedback analysis into tiny hearing aids.

Sixty years ago scientists examined the hair cells in the cochlea and observed “dead zones.” However, not until relatively recently did engineers learn how to take the sound and information from one frequency zone—where the patient had no usable hearing—and transpose this sound and information into another zone, where the patient had good hearing.

Since the 1950s, we have learned a lot about brain plasticity and how to teach people with very poor hearing to recognize words using their residual hearing and lip reading.

The improvements in hearing aid technology and auditory rehabilitation over the past 60 years have been miraculous. The lives of patients have been greatly enhanced. In this series of posts, we will be writing about some individual patients whose careers have been resurrected by high-tech hearing aids.

But, hearing aids are only half of the story. I will also discuss the skills that are needed to program and fit these advanced instruments.

See you next time.


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