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James West - Inventor of the Electret Microphone

02/26/2015

We thank Dr. Nina Atchley for contributing this week’s blog post in recognition of Black History month.

As February is Black History month we’d like to recognize James West, an important African-American inventor. Without his contributions to microphone technology we wouldn’t be able to offer the smaller, more discreet hearing aids we have today.

James West was born in Farmville, Prince Edward County, Virginia, on February 10, 1931, and set his sights on a career in electronics when he was barely nine years old after experiencing the power of electricity firsthand during a nearly-tragic encounter while plugging in an old radio. Though he initially pursued a degree in medicine at the behest of his parents, West eventually attended Temple University and obtained a degree in physics, while interning in the summers at Bell Laboratories in New Jersey.

In 1957, West was hired by Bell Labs as a full-time acoustical scientist. It was there that he teamed up with fellow scientist Gerhard M. Sessler and invented the electret transducer, which they developed into the electret microphone in 1962. More compact than previously available microphones, the electret microphone had a smooth response and low cost of production. The microphone was in mass production by 1968 and quickly became the industry standard. An estimated 90 percent of all microphones in use today, including those found in hearing aids, utilize this technology.

James West was named Inventor of the Year by the state of New Jersey in 1995, elected President of the Acoustical Society of America and member of the Academy of Engineering in 1998, and was inducted into the Inventor’s Hall of Fame in 1999. He continues to innovate and currently holds close to 50 U.S. patents and over 200 foreign patents. He received an honorary Doctorate of Science from the New Jersey Institute of Technology in 2000. As of this writing he is employed as a research professor at Johns Hopkins University.

The electret microphone revolutionized hearing aids.

So why was the development of the inexpensive electret microphone so important to the development of smaller, more discreet hearing aids? A number of components are necessary for amplification. Sound enters the hearing aid through the microphone, which converts the vibration to an electrical signal. The signal travels to an amplifier where it is made more powerful. The amplified signal is sent to the receiver, which converts it back into sound that then travels into your ear.

The advent of the carbon microphone, telephone, and vacuum tube led to the development of the first electronic hearing aids towards the end of the 19th century. However, due to the large size of the components, the hearing aids were barely portable, let alone wearable —in fact, a battery pack had to be strapped to the wearer’s leg! It wasn’t until the late 1940s, with the development of the button battery and integrated circuit, hearing aids became smaller and easier to wear. By 1955, the first ear level instrument was introduced in an eyeglass hearing aid, which integrated a hearing aid into eyeglass frames. With further component miniaturization over the next few years, the behind-the-ear (BTE) hearing aid was developed.

Although electronic components continued to shrink in size throughout the first half of the 20th century, there was still a limit as to how small a hearing aid could be made, because microphones used in hearing aids were still too sensitive to mechanical vibrations to be contained in a small case with a receiver. In 1974, audiologist Dr. Mead Killion and electroacoustic engineer Elmer Carlson created a micro-sized version of West and Sessel’s electret microphone. This micro-electret microphone had a much smoother response than the ceramic microphone widely used in hearing aids of the time, and more importantly was less sensitive to mechanical vibrations in small spaces. This opened the way for companies like Siemens to develop smaller and more discreet in-the-ear (ITE) and BTE hearing aids.

So, the next time you slip on a pair of tiny hearing aids, thank James West for helping to make them possible!

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