Etymotic Research Isolator ER-6, ER-15, ER-20, ER-25, ER-9 Fittings Manual

ER-4 MicroPro™Reference Quality Earphones

are popular among audiophiles for personal listening
(e.g. CD and MP3 players). ER-4 earphones are high
fidelity transducers developed specifically to combine
flat frequency response with isolation from external
noise. They deliver transparent, reference quality
sound and provide at least 20-25 dB of external noise
exclusion at all frequencies, which allows listeners to
hear the full dynamic range of recorded or live music
at safe levels. Many stage performers and recording
engineers use ER-4 earphones as in-ear monitors to
monitor or isolate their own and others’ instruments
or voices from the rest of the band or mix.

ER-6 Isolator™Earphones are a low-cost version
of the ER-4 earphones, with a higher accuracy
score than all other earphones and earbuds in their
class. Sound Isolation is 15-20 dB. With a special
adapter, ER-6 earphones can plug directly into your
Musicians Earplugs.

Musicians Earplugs

In the late 1970s
Elmer Carlson, an engineer
at Knowles Electronics,
developed what we now
call Musicians Earplugs.
His design replicated the
natural response of the ear
canal so that sound heard with
these earplugs would have the same
quality as the original, just quieter.

In 1985, while consulting with the Chicago
Symphony Orchestra, Mead Killion, Ph.D., president
and founder of Etymotic Research, concluded that
there was a real need for Carlson’s earplugs.

Mean Attenuation Characteristics
of Musicians Earplugs

ER-9

The ER-9 has reduced diaphragm stiffness for

less attenuation.

ER-25

The ER-25 has an increased diaphragm stiffness
and an acoustic-mass channel molded into the button
for more attenuation.

Ready-Fit Earplugs

ER-20 High Fidelity
Earplugs were developed

to provide low-cost,
one-size-fits-most high
fidelity earplugs that can
be used in a variety of noisy environments.

The goal of the ER-20 design was the same as for
Musicians Earplugs: to reduce noise but preserve
sound quality; in effect, to turn down the noise but
not muffle voices, environmental sounds or music.

ER-20s use a tuned resonator and acoustic
resistor to give essentially equal sound reduction
at all frequencies which preserves the fidelity of
the original sound.

Lost high frequencies with conventional earplugs, com­pared to response of ER-20 High Fidelity Earplugs

Diagram of the ER-20

Schematic side view
of the ER-15

C = compliance
L = inductance
R = resistance

Open ear response of the average ear measured in a
diffuse field or reverberant room. The response of the
ER-15 Musicians Earplug indicates a 15 dB reduction in
eardrum sound pressure at each frequency.

High Accuracy, Noise Isolating Earphones

History and Design of Flat Response Attenuators

EARPLUG ATTENUATION (Sound Reduction)

Mean Attn.

UNPROTECTED EAR

15 dB

WITH ER-15 EARPLUG

ER-15

ER-9

ER-25

FOAM

EARPLUG ATTENUATION (Sound Reduction)

Mean Attn.

ER-20 HI FI EARPLUGS

FOAM E-A-R PLUGS
(shallow insertion)

FOAM E-A-R PLUGS
(deep insertion)

30

20

10

0

-10

Real-Ear Attenuation in dB

-20

-30
125 250 500

1000 2000

4000

8000

-10

0

10

20

30

Real-Ear Attenuation in dB

40

50

125 250 500

Frequency (Hz)

1000 2000

4000

8000

-10

0

10

20

30

Real-Ear Attenuation in dB

40

50

125 250 500

1000 2000

Frequency (Hz)

4000

8000