Etymotic ER-3C Insert Earphones Calibration Manual

Single-Use-Eartips is a trademark of

Grason Associaties, Inc.

ER003446-B

INSERT EARPHONES

Calibration Manual

ACCESSORIES AND REPLACEMENT PARTS

Accessories and replacement parts are available from Etymotic Research, Inc.

and its authorized distributors.

Manfacturer

Etymotic Research, Inc.

61 Martin Lane

Elk Grove Village, IL 60007 USA

Phone: 847-228-0006

Toll free (U.S.): 888-389-6684

Facsimile: 847-228-6836

Technical support: customer-ser[email protected]

www.etymotic.com

ER3-06

Single-Use Eartips

Adapter with Tubing

ER3-06X

Single-Use Eartips

Adapter

ER3C-84

7' Cable with

Dual-Mono

6.33 mm

(1/4") plugs

ER3-21

Sound Delivery Tube

Replacements with

Adapters

ER3-04

Sound Delivery Tube Adapters

ER3-05

Hook-and-Loop Clips

ER10D-T05

5 mm

Single-Use Eartips

™

ER10D-T03

3 mm

ER10D-T04

4 mm

ER10D-T06

6 mm

ER10D-T07

7 mm

ER10D-T08

8 mm

ER10D-T09

9 mm

ER10D-T010

10 mm

ER10D-T011

11 mm

ER10D-T013

13 mm

ER10D-T016

16 mm

ER10D-T012

12 mm

ER10D-T014

14 mm

ER3-14C

18 mm Disposable Foam Eartips

ER3-14A

13 mm Disposable Foam Eartips

ER3-14B

10 mm Disposable Foam Eartips

ER3-14E

4 mm Disposable Eartips

ER3-14D

3.5 mm Disposable Eartips

PRIOR TO CALIBRATION

• Conﬁrm that the earphone impedance matches the requirements of the audiometric

equipment. Labels on the earphones identify the impedance.

•

Unless the audiometer was purchased with ER-3C earphones precalibrated by the

audiometric equipment manufacturer, the Reference Equivalent Threshold Sound

Pressure Levels (RETSPL) values and procedure cited in the current version of the

ANSI S3.6 or IEC Standard must be used to calibrate the equipment prior to initial use.

• Correction factors can be applied where it is necessary to alternate between insert

earphones and supra-aural earphones when using audiometers that do not provide

a dual-calibration option.

ACOUSTIC COUPLING METHODS TO COMPLY WITH

MEASUREMENT STANDARDS

ANSI IEC

Occluded Ear

Simulator Coupler

S3.25

use ER3-14A

or ER-3-08

60318-4

use ER3-14A

or ER-3-08

2-cc Coupler

S3.7

HA-1 use ER3-14A

HA-2 use rigid tube

60318-5

use ER3-14A

or ear mould simulator

0.4-cc Coupler

CD 62866

use ER3-14A

2 3

CALIBRATION IN FOUR COUPLERS

The table below shows the Reference Equivalent Threshold Sound Pressure Levels

(RETSPLs) measured in four couplers.

Audiometer calibration is normally performed at a dial setting of 70 dB HL.

The calibration targets shown in parentheses next to the RETSPL numbers above

were obtained by adding 70 dB to each RETSPL number.

ANSI S3.6 (2010) AND ISO 389.2 (1994) REFERENCE THRESHOLDS

Sound Pressure Levels in dB re. 20μPa

Occluded Ear HA-2 with 2-cc Coupler 0.4-cc Coupler

Frequency (Hz) Simulator Rigid Tube HA-1 (Provisional)

125 28.0 (98.0) 26.0 (96.0) 26.5 (96.5) 33.0 (103.0)

250 17.5 (87.5) 14.0 (84.0) 14.5 (84.5) 25.5 (95.5)

500 9.5 (79.5) 5.5 (75.5) 6.0 (76.0) 18.0 (88.0)

750 6.0 (76.0) 2.0 (72.0) 2.0 (72.0) 13.5 (83.5)

1000 5.5 (75.5) 0.0 (70.0) 0.0 (70.0) 12.0 (82.0)

1500 9.5 (79.5) 2.0 (72.0) 0.0 (70.0) 12.0 (82.0)

2000 11.5 (81.5) 3.0 (73.0) 2.5 (72.5) 14.5 (84.5)

3000 13.0 (83.0) 3.5 (73.5) 2.5 (72.5) 14.5 (84.5)

4000 15.0 (85.0) 5.5 (75.5) 0.0 (70.0) 13.0 (83.0)

6000 16.0 (86.0) 2.0 (72.0) -2.5 (67.5) 10.5 (80.5)

8000 15.5 (85.5) 0.0 (70.0) -3.5 (66.5) 10.5 (80.5)

Speech

1-kHz Cal. Tone 18 (88.0) 12.5 (82.5) 12.5 (82.5) 24.5 (94.5)

CALIBRATION FOR SPEECH AUDIOMETRY

To calibrate ER-3C insert earphones for a speech signal:

• Set a 1-kHz pure tone signal at 0 Volume Units (VU) through the

speech (microphone) circuit

• Set the audiometer attenuator to 70 dBHL

• Adjust the speech circuit on the audiometer to measure 82.5 (70.0 + 12.5) dB SPL

in a 2-cc coupler. A range of 79.5 to 85.5 meets the ± 3-dB tolerance allowed in

the standard.

The ANSI standard speciﬁes that a 1-kHz reference tone level for the speech

circuit should be 12.5 dB above a 1-kHz reference test threshold for any earphone.

The 1-kHz RETSPL for ER-3 Series earphones is 0 dB SPL. (70 + 0 + 12.5 = 82.5).

A range of 79.5 to 85.5 dB meets the ±3 dB tolerance allowed in the ANSI standard.

PRIOR TO CALIBRATION

• Conﬁrm that the earphone impedance matches the requirements of the audiometric

equipment. Labels on the earphones identify the impedance.

•

Unless the audiometer was purchased with ER-3C earphones precalibrated by the

audiometric equipment manufacturer, the Reference Equivalent Threshold Sound

Pressure Levels (RETSPL) values and procedure cited in the current version of the

ANSI S3.6 or IEC Standard must be used to calibrate the equipment prior to initial use.

• Correction factors can be applied where it is necessary to alternate between insert

earphones and supra-aural earphones when using audiometers that do not provide

a dual-calibration option.

ACOUSTIC COUPLING METHODS TO COMPLY WITH

MEASUREMENT STANDARDS

ANSI IEC

Occluded Ear

Simulator Coupler

S3.25

use ER3-14A

or ER-3-08

60318-4

use ER3-14A

or ER-3-08

2-cc Coupler

S3.7

HA-1 use ER3-14A

HA-2 use rigid tube

60318-5

use ER3-14A

or ear mould simulator

0.4-cc Coupler

CD 62866

use ER3-14A

2 3

CALIBRATION IN FOUR COUPLERS

The table below shows the Reference Equivalent Threshold Sound Pressure Levels

(RETSPLs) measured in four couplers.

Audiometer calibration is normally performed at a dial setting of 70 dB HL.

The calibration targets shown in parentheses next to the RETSPL numbers above

were obtained by adding 70 dB to each RETSPL number.

ANSI S3.6 (2010) AND ISO 389.2 (1994) REFERENCE THRESHOLDS

Sound Pressure Levels in dB re. 20μPa

Occluded Ear HA-2 with 2-cc Coupler 0.4-cc Coupler

Frequency (Hz) Simulator Rigid Tube HA-1 (Provisional)

125 28.0 (98.0) 26.0 (96.0) 26.5 (96.5) 33.0 (103.0)

250 17.5 (87.5) 14.0 (84.0) 14.5 (84.5) 25.5 (95.5)

500 9.5 (79.5) 5.5 (75.5) 6.0 (76.0) 18.0 (88.0)

750 6.0 (76.0) 2.0 (72.0) 2.0 (72.0) 13.5 (83.5)

1000 5.5 (75.5) 0.0 (70.0) 0.0 (70.0) 12.0 (82.0)

1500 9.5 (79.5) 2.0 (72.0) 0.0 (70.0) 12.0 (82.0)

2000 11.5 (81.5) 3.0 (73.0) 2.5 (72.5) 14.5 (84.5)

3000 13.0 (83.0) 3.5 (73.5) 2.5 (72.5) 14.5 (84.5)

4000 15.0 (85.0) 5.5 (75.5) 0.0 (70.0) 13.0 (83.0)

6000 16.0 (86.0) 2.0 (72.0) -2.5 (67.5) 10.5 (80.5)

8000 15.5 (85.5) 0.0 (70.0) -3.5 (66.5) 10.5 (80.5)

Speech

1-kHz Cal. Tone 18 (88.0) 12.5 (82.5) 12.5 (82.5) 24.5 (94.5)

CALIBRATION FOR SPEECH AUDIOMETRY

To calibrate ER-3C insert earphones for a speech signal:

• Set a 1-kHz pure tone signal at 0 Volume Units (VU) through the

speech (microphone) circuit

• Set the audiometer attenuator to 70 dBHL

• Adjust the speech circuit on the audiometer to measure 82.5 (70.0 + 12.5) dB SPL

in a 2-cc coupler. A range of 79.5 to 85.5 meets the ± 3-dB tolerance allowed in

the standard.

The ANSI standard speciﬁes that a 1-kHz reference tone level for the speech

circuit should be 12.5 dB above a 1-kHz reference test threshold for any earphone.

The 1-kHz RETSPL for ER-3 Series earphones is 0 dB SPL. (70 + 0 + 12.5 = 82.5).

A range of 79.5 to 85.5 dB meets the ±3 dB tolerance allowed in the ANSI standard.

Stimulus/measurement equipment must be capable of sourcing the required

electrical drive across the load impedance. For the ER-3, a minimum of 2V RMS

constant voltage drive across a 10-Ohm load with Z

OUT

< 1 Ohm.

PROCEDURE

1. Make all required acoustic and electrical connections.

2. Either a Calibration Adapter/Insert or a foam eartip must be used to form

an acoustic sealed system. For the ER-3, the overall acoustic length

from the housing to the coupler reference plane is 278 mm.

3. Apply suitable stimulus signal from the measurement system

(e.g., 20 Hz to 20 KHz swept sine or a broadband chirp).

4. Measure frequency response and calculate sensitivity calibration based

on the known sensitivity of the coupler microphone and associated

preampliﬁer/system gain.

INSERT EARPHONE SENSITIVITY CALIBRATION

EQUIPMENT AND PROCEDURE

Acoustic coupler from the list below (with measurement microphone, preampliﬁer,

cable and power supply):

• Full bandwidth calibration (occluded ear simulator):

Knowles DB-100 ‘Zwislocki’ ANSI S3.25 type Occluded Ear Simulator

G.R.A.S. RA0045 IEC 60318-4 type Occluded Ear Simulator (or equivalent)

• Limited bandwidth calibration (ANSI S3.7 / IEC 60318-5 type 2cc HA-2 coupler):

G.R.A.S. RA0113 (for 1" mic), RA0038 (for ½" mic), Bruel & Kjaer DB-0138,

or equivalent

Acoustic Coupler ERI Adapter

Knowles DB-100; G.R.A.S RA0045 ER3-08 for ER-3 Series

G.R.A.S RA0113; RA0038; B&K DB0138 N/A

G.R.A.S. RA0252 N/A

Adapter: Insert or Foam Eartip

-30

-20

-10

100 1000 10000

Relative Response in dB

Frequency (Hz)

ER-3C Response in Four Couplers

Occluded Ear Simulator

GRAS RA0045

0.4-cc

GRAS RA0252

2-cc (HA-1)

GRAS RA0038

2-cc (HA-2) with Ear Mould Simulator/Rigid Tube

GRAS RA0038

-30

-20

-10

100 1000 10000

Relative Response in dB

Frequency (Hz)

ER-3C Response in Four Couplers

Occluded Ear Simulator

GRAS RA0045

0.4-cc

GRAS RA0252

2-cc (HA-1)

GRAS RA0038

2-cc (HA-2) with Ear Mould Simulator/Rigid

Tube

GRAS RA0038

ER-3 Series Earphones in Four Couplers

FREQUENCY RESPONSE IN FOUR COUPLERS

The numbers in the table on page 3 were chosen to produce the same calibration

regardless of coupler. In other words, an earphone calibrated to 70 dB SPL at 1 kHz

in either of the 2-cc couplers should produce 75.5 dB SPL at the average eardrum

or in an occluded ear simulator.

The graph below shows the frequency response of an ER-3 Series earphone

measured in each of four couplers. For the Ear Simulator curve, the ER3 eartip

was sealed directly into the coupler rather than through an HA-2 sound channel

as speciﬁed in ANSI S3.6-2010. The response measured with the eartip sealed

in the coupler is nearly identical to the average eardrum pressure produced by an

nsert earphone such as the ER-3 Series (Sachs and Burkhard, 1972). The HA-2 sound

channel introduces an extraneous high-frequency boost in the coupler measurement.

4 5

COUPLER CONNECTIONS

Stimulus/measurement equipment must be capable of sourcing the required

electrical drive across the load impedance. For the ER-3, a minimum of 2V RMS

constant voltage drive across a 10-Ohm load with Z

OUT

< 1 Ohm.

PROCEDURE

1. Make all required acoustic and electrical connections.

2. Either a Calibration Adapter/Insert or a foam eartip must be used to form

an acoustic sealed system. For the ER-3, the overall acoustic length

from the housing to the coupler reference plane is 278 mm.

3. Apply suitable stimulus signal from the measurement system

(e.g., 20 Hz to 20 KHz swept sine or a broadband chirp).

4. Measure frequency response and calculate sensitivity calibration based

on the known sensitivity of the coupler microphone and associated

preampliﬁer/system gain.

INSERT EARPHONE SENSITIVITY CALIBRATION

EQUIPMENT AND PROCEDURE

Acoustic coupler from the list below (with measurement microphone, preampliﬁer,

cable and power supply):

• Full bandwidth calibration (occluded ear simulator):

Knowles DB-100 ‘Zwislocki’ ANSI S3.25 type Occluded Ear Simulator

G.R.A.S. RA0045 IEC 60318-4 type Occluded Ear Simulator (or equivalent)

• Limited bandwidth calibration (ANSI S3.7 / IEC 60318-5 type 2cc HA-2 coupler):

G.R.A.S. RA0113 (for 1" mic), RA0038 (for ½" mic), Bruel & Kjaer DB-0138,

or equivalent

Acoustic Coupler ERI Adapter

Knowles DB-100; G.R.A.S RA0045 ER3-08 for ER-3 Series

G.R.A.S RA0113; RA0038; B&K DB0138 N/A

G.R.A.S. RA0252 N/A

Adapter: Insert or Foam Eartip

-30

-20

-10

100 1000 10000

Relative Response in dB

Frequency (Hz)

ER-3C Response in Four Couplers

Occluded Ear Simulator

GRAS RA0045

0.4-cc

GRAS RA0252

2-cc (HA-1)

GRAS RA0038

2-cc (HA-2) with Ear Mould Simulator/Rigid Tube

GRAS RA0038

-30

-20

-10

100 1000 10000

Relative Response in dB

Frequency (Hz)

ER-3C Response in Four Couplers

Occluded Ear Simulator

GRAS RA0045

0.4-cc

GRAS RA0252

2-cc (HA-1)

GRAS RA0038

2-cc (HA-2) with Ear Mould Simulator/Rigid

Tube

GRAS RA0038

ER-3 Series Earphones in Four Couplers

FREQUENCY RESPONSE IN FOUR COUPLERS

The numbers in the table on page 3 were chosen to produce the same calibration

regardless of coupler. In other words, an earphone calibrated to 70 dB SPL at 1 kHz

in either of the 2-cc couplers should produce 75.5 dB SPL at the average eardrum

or in an occluded ear simulator.

The graph below shows the frequency response of an ER-3 Series earphone

measured in each of four couplers. For the Ear Simulator curve, the ER3 eartip

was sealed directly into the coupler rather than through an HA-2 sound channel

as speciﬁed in ANSI S3.6-2010. The response measured with the eartip sealed

in the coupler is nearly identical to the average eardrum pressure produced by an

nsert earphone such as the ER-3 Series (Sachs and Burkhard, 1972). The HA-2 sound

channel introduces an extraneous high-frequency boost in the coupler measurement.

4 5

COUPLER CONNECTIONS

Maximum Permissible Ambient Noise Levels

The current ANSI Standard “Maximum Permissible Ambient Noise Levels (MPANLs)

for Audiometric Test Rooms” [(ANSI S3.1-1999) (R2013)] includes octave band and

one-third octave band permissible noise levels for both supra-aural and ER-3 Series

insert earphones. The ANSI octave band MPANLs are shown in the table below

for standard earphones and for ER-3 Series earphones with fully inserted ER3 eartips.

Ears covered: Octave band MPANLs using a supraaural or insert earphone for three

test frequency ranges re: 20 uPa to the nearest 0.5 dB are shown in table below.

The ears-covered MPANLs shown in the above table were derived using mean

earphone attenuation values. To decrease the chance that individual listeners for

whom less than average attenuation is obtained will experience threshold shift, the

MPANLs can be lowered by reducing the predicted level of earphone attenuation.

The net effect would be that the MPANLs would be lower (stricter criteria) for

ears-covered testing, and cover approximately 84% of all persons tested. The

standard deviations for insert earphones for 125 to 8000 Hz are 3 dB to 6 dB.

Refer to ANSI S3.1 Table 1 for speciﬁc standard deviation values by frequency.

REFERENCES

1. American National Standards Institute. ANSI S3.1 – 1999 (R2013). Maximum Permissible Ambient Noise

Levels for Audiometric Test Rooms.

2. American National Standards Institute. ANSI S3.25 – 2009 (R2014). Occluded Ear Simulator.

3. American National Standards Institute. ANSI S3.6 – 2010. Speciﬁcation for Audiometers.

4. American National Standards Institute. ANSI S3.7 – 1995 (R2008). Methods for Coupler Calibration of

Earphones.

5. International Organization for Standardization. ISO 389-2: 1994 (R2014). Acoustics – Reference zero for

the calibration of audiometric equipment – Part 2: Reference equivalent threshold sound pressure levels

for pure tones and insert earphones.

6. International Electrotechnical Commission. IEC 60318-4 Ed. 1.0b: 2010. Electroacoustics – Simulators

of human head and ear – Part 4: Occluded-ear simulator for the measurement of earphones coupled to

the ear by means of ear inserts.

7. International Electrotechnical Commission. IEC 60318-5 Ed. 1.0b: 2006. Electroacoustics – Simulators

of the human head and ear – Part 5: 2cm3 coupler for the measurement of hearing aids and earphones

coupled to the ear by means of ear inserts.

8. Killion MC (1978). Revised estimate of minimum audible pressure: Where is the missing 6 dB? J.

Acoust. Soc. Am., 63(5), 1501-1508.

9. Wilbur LA, Kruger B, Killion MC (1988). Reference thresholds for the ER-3A insert earphone. J. Acoust.

Soc. Am., 83(2), 669-675.

10. Sachs RM, Burkhard M (1972). Pressure response in ears and couplers. IRPI Rep. 20021 to Knowles

Electronics, Franklin Park IL.

Octave

Band

Intervals

Supra-aural Earphone ER-3 Series Full Insertion

125

250

500

1000

2000

4000

8000

125 -

8,000 Hz

250 -

8,000 Hz

500 -

8,000 Hz

125 -

8,000 Hz

250 -

8,000 Hz

500 -

8,000 Hz

35.0

25.0

21.0

26.0

34.0

37.0

39.0

25.0

21.0

26.0

34.0

37.0

49.0

35.0

21.0

26.0

34.0

37.0

59.0

53.0

50.0

47.0

49.0

50.0

56.0

67.0

53.0

50.0

47.0

49.0

50.0

56.0

78.0

64.0

50.0

47.0

49.0

50.0

56.0

6 7

APPENDIX

The graphs at right show the

RETSPLs from ANSI S3.6-1989

and ANSI S3.6-1996. The 1996

values were based on three studies

(two European and one U.S.). They

were adopted in the U.S. in the

interest of international harmony.

The 1996 values are the ones used

for normal audiometer calibration

in the U.S. to comply with legal

requirements for proper calibration.

Those values are presently equal

to the relevant values in international

IEC and ISO 389-2 standards.

For purposes of hearing research,

the ANSI S3.6-1989 values should

be considered: The values were

originally based on a compilation

of 35 studies from 1928 to 1977

(Killion, 1978), and validated by ﬁve

threshold studies using the ER-3A

insert earphones (Wilber et al., 1988).

The RETSPL numbers in the

ANSI 1989 Occluded Ear Simulator

are the same

as the Minimum

Audible Pressure at the Eardrum

(MAPD) numbers. (Killion,1978).