Interview with Dr. Mead Killion


What makes your company unique?

Etymotic Research is a research, development and manufacturing company that designs products to measure, enhance and protect hearing. All of Etymotic's products are for the ear. We have developed everything from high fidelity hearing aid integrated circuits to high fidelity hearing protection. What makes us unique is our combination of expertise in electroacoustics and hearing science. Scientists, engineers, and audiologists working together have generated over 100 patents. The audiologists in particular bring an indepth knowledge of how people hear and how that will affect earphone performance.

Etymotic earphones are used in audiology clinics, research laboratories, recording studios, onstage by performing artists and by travelers. Etymotic now has competitors in several product categories. Not one matches the performance of Etymotic products.

What distinguishes you from the competition?

Etymotic Research has the distinction of being the first company to develop high fidelity insert earphones. The ER-1 and ER-2 earphones, introduced in 1984, were developed for use in auditory research. Each successive innovation, up through the present, has refined this technology for different user groups. Competitive analyses, conducted by independent laboratories following industry standards, indicate that Etymotic earphones have the highest noise isolation of all noise-canceling earphones (in some cases twice as much). Etymotic's own measurements indicate that our earphones have the highest frequency response accuracy of all in-the-ear earphones, by a significant margin.

Why don't other manufacturers make earphones with the same performance?

Part of the reason is probably cost. Most earphones are built with lowcost driver elements that don't permit an accurate frequency response.

Is that all?

No. I think the main reason is a lack of understanding of what a highfidelity earphone needs to do. There have been three major studies of the sound pressure developed at the eardrum by a sound field: Wiener and Ross (1946), Shaw (1976), and Killion and Monser (1978). All showed a nearly identical frequency response that included a 15 dB boost in pressure at 2.8 kHz coming from the combined resonance and horn action of the concha and ear canal. When you insert an earphone in the ear, it destroys this resonance, so an earphone with a "flat" response at the eardrum sounds very dull, which you can hear for yourself in some of the products at CES.

So you tailor the response of the earphone to match the natural resonance of the open ear?

Yes, with one additional shaping thrown in. Probably 99% of all CDs have a 5 dB highfrequency boost built in. This is fortunate because the best available loudspeakers have about a 5 dB roll off at 10 kHz in their room response. Part of this is from the absorption of curtains and carpeting, but Schulein (1975) measured many studio monitor loudspeakers and found the same rolloff.

How would I find the ideal curve for a highfidelity earphone?

Etymotic Research is the only insert earphone company to publish the target curve that represents the listener's eardrum pressure response for near perfect fidelity. That target curve is included with all of our published data sheets.

Is there anything else to add?

Yes. In designing any system, it helps to know where you should concentrate your energy. I was fortunate in the 1970s to correspond with Larry Seligson of Consumers Union about the "Accuracy score" they used in rating loudspeakers. Consumer Reports stated that they could predict listeners' loudspeaker ratings within 8% from a calculation based on onethirdoctave frequency response measurements converted to loudness in sones. The average error in loudness from a perfect system, subtracted from 100%, gave the accuracy score. I extended their 21band calculation to a 25band calculation and included it in my Ph.D. research at Northwestern. I confirmed the excellent correlation Consumer Reports had reported between fidelity ratings and accuracy scores using three separate groups (one included Julian Hirsh of Stereo Review) listening to loudspeakers, earphones, and hearing aids. We routinely use the 25band accuracy score in all of our design programs, and report the results on our data sheets. Our ER4S obtains a score of 92%, which puts it above most loudspeakers and well above competitive intheear earphones. The accuracy score is probably the single most important tool for earphone design.

To what do you attribute your Company's success?

Etymotic Research is an engineering-driven company. Its mission, to develop products for the ear, has not changed in over 25 years. New product development reflects our commitment to improve the lives of those with hearing loss and to enhance the listening experience of musicians and music lovers everywhere. Just as important, we still have the first seven engineers we hired. Their combined 150 years of experience makes them invaluable when we face new design challenges or new problems that arise with existing designs.

What new products are on the horizon?

Companion Mics®, a system that allows persons with hearing loss to communicate with their companions when they are in noisy places; electronic hearing protection for military, gunsports, motorsports and music applications, and safe-listening earphones for children.