USOO8649546B2

(12) United States Patent (10) Patent No.: US 8,649,546 B2

Haapapuro et al. (45) Date of Patent: Feb. 11, 2014
(54) INSERT EARPHONE USING AMOVING COIL (58) Field of Classification Search
DRIVER USPC .................. 381/337 366,370 372, 380 .382
See application file for complete search history.
(75) Inventors: Andrew J. Haapapuro, Arlington
Heights, IL (US); Viorel Drambarean, (56) References Cited
Skokie, IL (US); Mead C. Killion, Elk
Grove Village, IL (US) U.S. PATENT DOCUMENTS

(73) Assignee: Etymotic Research, Inc., Elk Grove 5,022.486 A * 6/1991 Miura et al. .................. 381.382
Village, IL (US) 5,668,883 A * 9/1997 Abe et al. ........................ 381/72
8,055,007 B2 * 1 1/2011 Kim ................... ... 381.382
8, 107,665 B2* 1/2012 Haapapuro et al. ........... 381,380
(*) Notice: Subject to any disclaimer, the term of this
patent is extended or adjusted under 35 * cited by examiner
U.S.C. 154(b) by 77 days.
Primary Examiner — Suhan Ni
(21) Appl. No.: 13/338,970 (74) Attorney, Agent, or Firm — McAndrews, Held &
Malloy, Ltd.
(22) Filed: Dec. 28, 2011
(65) Prior Publication Data (57) ABSTRACT
US 2012/O163649 A1 Jun. 28, 2012 Certain embodiments provide an insert earphone assembly.
The insert earphone assembly may include a transducer
Related U.S. Application Data adapted to convert electrical signals into Sound energy. The
insert earphone assembly may also include a main Sound
(62) Division of application No. 1 1/699.910, filed on Jan. channel adapted for communicating the Sound energy to a
30, 2007, now Pat. No. 8,107,665. user. The insert earphone assembly may also include a plu
(60) Provisional application No. 60/763,264, filed on Jan. rality of one or more damping elements, one or more auxiliary
30, 2006, provisional application No. 60/803,440, Volumes, and one or more auxiliary ducts. The plurality of the
filed on May 30, 2006. one or more damping elements, the one or more auxiliary
Volumes, and the one or more auxiliary ducts may be adapted
(51) Int. C. to absorb sound from the main sound channel to modify at
H04R 25/00 (2006.01) least one insertion response.
(52) U.S. C.
USPC ............................ 381/380; 381/370; 381/.382 16 Claims, 20 Drawing Sheets

528A
U.S. Patent Feb. 11, 2014 Sheet 1 of 20 US 8,649,546 B2

FIG. 1
Killion, Berger, Nuss Average Ear Response

130
120
110
100
90
80
70
10 100 1000 10000
U.S. Patent Feb. 11, 2014 Sheet 2 of 20 US 8,649,546 B2

FIG. 2
Response at the Eardrum
130 0.1 Wrms Drive

25 Band ACcuracy Score

10 100 1000 10000

Frequency in HZ
- Earphone Response ....... HIFTarget - Perceived Response
Response at the Eardrum
0.1 Wrms Drive
130
120
3890- ...-acon -alue"
as NUs. w
8O 25 Band ACCuracy Score
70
60
50
10 100 1000 10000
Frequency in HZ
- Earphone Response . . . HIFTarget - Perceived Response
Response at the Eardrum
0.1 Wrms Drive

25 Band ACCuracy Score

10 100 1000 10000

Frequency in HZ
- Earphone Response ....... HIFTarget - Perceived Response
U.S. Patent Feb. 11, 2014 Sheet 3 of 20 US 8,649,546 B2

Response at the Eardrum

0.1 Wrms Drive

130 iPOdin-Ear MOcel

120

CfO
110
onO 100

2 90 25 Band ACCuracy Score 46.7%

3. 80
8Y

10 100 1000 10000

Frequency in HZ
- Earphone Response ..........HIFTarget - Perceived Response
U.S. Patent Feb. 11, 2014 Sheet 4 of 20 US 8,649,546 B2

FIG. 4
Response at the Eardrum
0.1 Wrms Drive

130
Shure E2C
120
110
100
90
80
70
60
50
10 100 1000 10000
Frequency in HZ
- EarphOne Response ......... HIFTarget - Perceived Response
U.S. Patent Feb. 11, 2014 Sheet 5 of 20 US 8,649,546 B2

s i
NY
U.S. Patent Feb. 11, 2014 Sheet 6 of 20 US 8,649,546 B2

s
U.S. Patent Feb. 11, 2014 Sheet 7 of 20 US 8,649,546 B2

s
U.S. Patent Feb. 11, 2014 Sheet 8 of 20 US 8,649,546 B2

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SUW' eS 90
U.S. Patent Feb. 11, 2014 Sheet 9 of 20 US 8,649,546 B2

–1 |
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U.S. Patent Feb. 11, 2014 sheet 10 of20 US 8,649.546 B2
U.S. Patent Feb. 11, 2014 Sheet 11 of 20 US 8,649,546 B2
U.S. Patent Feb. 11, 2014 Sheet 12 of 20 US 8,649,546 B2
U.S. Patent Feb. 11, 2014 Sheet 14 of 20 US 8,649,546 B2

FIG. 5

10 100 1000 10000 100000

Frequency (Hz)
U.S. Patent Feb. 11, 2014 Sheet 15 of 20 US 8,649,546 B2

FIG. 6

10 100 1000 10000 100000

Frequency Hz
U.S. Patent Feb. 11, 2014 Sheet 16 of 20 US 8,649,546 B2

FIG. 7

10 100 1000 10000 100000

Frequency Hz
U.S. Patent Feb. 11, 2014 Sheet 17 of 20 US 8,649,546 B2

FIG. 8A

0.024 0.1 1.0 10.0 20.0

Frequency (kHz)
U.S. Patent Feb. 11, 2014 Sheet 18 of 20 US 8,649,546 B2

FIG. 8B

AH-13C

AH-13D

10 100 1000 10000 100000

Frequency Hz
U.S. Patent Feb. 11, 2014 Sheet 19 of 20 US 8,649,546 B2

FIG. 9A
Response at the Eardrum
0.1 WrmS DRIVE

11O

90
25Band ACCuracy Score 75% NA W"

10 100 1000 10000

Frequency in HZ
- Earphone Response .......... HIFTarget - Perceived Response
U.S. Patent Feb. 11, 2014 Sheet 20 of 20 US 8,649,546 B2

FIG. 9B
Response at the Eardrum
0.1 WrmS DRIVE
130
120 BassBOOst
1 1O
100
90
25 Band ACCuracy Score 56.0%
80
70
60
50
10 100 1000 10000
Frequency in HZ
- Earphone Response ........ HIFTarget - Perceived Response
 US 8,649,546 B2
1. 2
INSERT EARPHONE USING AMOVING COIL FIG. 5A is a diagram illustrating exemplary acoustic con
DRIVER struction of a high accuracy moving coil design for an insert
earphone assembly with a complete form factor designed to
CROSS-REFERENCE TO RELATED fit deeply into the ear canal of a user, in accordance with an
APPLICATIONS/INCORPORATION BY embodiment of the invention.
REFERENCE FIG. 5B is a diagram illustrating exemplary acoustic con
struction of a high accuracy moving coil design for an insert
The present application is a divisional and claims priority earphone assembly with a complete form factor designed to
under 35 U.S.C. S 121 to copending U.S. patent application 10
fit deeply into the ear canal of a user, in accordance with an
Ser. No. 1 1/699,910, filed on Jan. 30, 2007, which claims embodiment of the invention.
priority under 35 U.S.C. S 119(e) to provisional application FIG. 5C is a diagram illustrating a portion of an insert
Ser. Nos. 60/763,264, filed on Jan. 30, 2006, and 60/803,440, earphone assembly using one or more acoustic resonant
filed on May 30, 2006. The entire contents of each above ducts, in accordance with an embodiment of the invention.
mentioned prior-filed application is hereby expressly incor 15 FIG. 5D illustrates exemplary graphs of frequency
porated herein by reference. responses of an insert earphone assembly using one or more
FIELD OF THE INVENTION resonant ducts, in accordance with an embodiment of the
invention.
Certain embodiments of the invention relate to sound pro FIG. 5E is a diagram illustrating a portion of an insert
cessing devices. More specifically, certain embodiments of earphone assembly using one or more resonant ducts, in
accordance with an embodiment of the invention.
the invention relate to a method and system for insert ear FIG. 5F is a diagram illustrating a portion of an insert
phone using a moving coil driver.
earphone assembly using one or more resonant ducts, in
BACKGROUND OF THE INVENTION accordance with an embodiment of the invention.
25 FIG. 5G is a schematic diagram of an exemplary passive
Use of insert earphones has risen considerably with the electrical filter, which may be utilized in connection with an
success of products like the Apple iPod. For the most part, the embodiment of the present invention.
consumer's purchasing decision may be motivated by price FIG.5H is a schematic diagram of an exemplary electrical
point more than by Sound quality. The electro-acoustic trans filter/bypass circuit for modifying bass response, which may
duction element traditionally used to create high-fidelity 30
be used in accordance with an embodiment of the invention.
insert earphones is the device based upon the balanced-arma FIG.5I is a graph illustrating the effect of an exemplary
ture design. The complexity and Subsequent high-manufac high pass filter for shaping the response of an insert earphone,
turing cost of this component is responsible for the high in accordance with an embodiment of the invention.
price-point of high-fidelity insert earphones. FIG. 5J is a graph illustrating the effect of an exemplary
Further limitations and disadvantages of conventional and 35
traditional approaches will become apparent to one of skill in high pass filter for shaping the response of an insert earphone,
in accordance with an embodiment of the invention.
the art, through comparison of Such systems with some FIG. 6 is a graph that illustrates an exemplary response of
aspects of the present invention as set forth in the remainder of an insert earphone with various levels of acoustic damping, in
the present application with reference to the drawings. accordance with an embodiment of the invention.
40
BRIEF SUMMARY OF THE INVENTION FIG. 7 is a graph that illustrates the effect on the frequency
response when the sealed rear Volume is varied, in accordance
An insert earphone assembly, Substantially as shown in with an embodiment of the invention.
and/or described in connection with at least one of the figures, FIG. 8A is a graph that illustrates a varied acoustic notch
as set forth more completely in the claims. 45 filter and its effect on frequency response, inaccordance with
Various advantages, aspects and novel features of the an embodiment of the invention.
present invention, as well as details of an illustrated embodi FIG. 8B is a graph that illustrates changes in frequency
ment thereof, will be more fully understood from the follow response of an insert earphone utilizing an auxiliary dia
ing description and drawings. phragm, in accordance with an embodiment of the invention.
50 FIG. 9A is a graph illustrating acoustic bass boost, in
BRIEF DESCRIPTION OF SEVERAL VIEWS OF accordance with an embodiment of the invention.
THE DRAWINGS FIG.9B is a graph illustrating bass boost, in accordance
with an embodiment of the invention.
FIG. 1 is an exemplary graph for estimating the average
human ear response, which may be used in accordance with 55 DETAILED DESCRIPTION OF THE INVENTION
an embodiment of the invention.
FIG. 2 illustrates exemplary graphs of responses at the Certain embodiments of the invention may be found in a
eardrum of moving coil designs using methods described method and system for insert earphone using a moving coil
herein to achieve high accuracy frequency responses. driver. Driver designs based on the moving-coil structure are
FIG. 3 illustrates an exemplary graph of responses at the 60 significantly less complicated and, therefore, less expensive.
eardrum of concha mounted or partially/full sealing units In accordance with an embodiment of the invention, an insert
currently on the market compared to the average human ear earphone may use a moving-coil driver to realize an insert
response as seen in FIG. 1. earphone device with optimal Sound quality and high isola
FIG. 4 illustrates an exemplary graph of responses at the tion of external noise at a very affordable price-point.
eardrum of concha mounted or partially/full sealing units 65 FIG. 1 is an exemplary graph for estimating the average
currently on the market compared to the average human ear human ear response, which may be used in accordance with
response as seen in FIG. 1. an embodiment of the invention.
 US 8,649,546 B2
3 4
Mead Killion, Elliott Berger and Robert Nuss have devel Depending on the natural acoustic behavior of a the mov
oped a composite curve to estimate the average human ear ing coil design of the insert earphone 500A, the combination
response, as illustrated in FIG. 1. of response shaping, resonant peak shifting and/or smoothing
Accuracy Score Defined. Accuracy score may be defined may require any combination of damping values, Sound chan
as a 25-band extension of a response accuracy rating system 5 nels, auxiliary Volumes, auxiliary compliances and/or elec
based upon the 1979 Consumers Union procedure applied to tronic filtering to shape the frequency response of the ear
loudspeaker assessment. It employs Stevens Mark VI loud phone 500A. In this regard, the frequency response of the
ness values to weight the importance of defects or “compro insert earphone 500A may be varied by utilizing a different
mises in the frequency response. The Accuracy Score has 10
number of damping elements, Sound channels, auxiliary
been shown to correlate strongly to subjective (e.g. jury) ducts, resonant ducts, and/or auxiliary Volumes. Furthermore,
assessments of signal (e.g. music) fidelity. frequency response of the insert earphone 500A may be var
In accordance with an embodiment of the invention, an ied by using one or more additional electronic components
insert earphone using a moving coil driver may be adapted to within the insert earphone, such as, for example, the compo
achieve a highest Accuracy Score of any moving coil design 15 nents disclosed herein below with regard to FIGS. 5C and 5D.
of 80% or higher. The highest accuracy score of moving coil In one embodiment of the invention, there may be two
designs in industry has been less than 70% accurate. This natural peaks close to the target peak frequency. In Such
applies to either concha mounted “earbuds' or partial/canal instances, damping elements 524A and/or 530A may be used
sealing models. to reduce both peaks to a desired shape. If the peak closest to
FIG. 2 illustrates exemplary graphs of responses at the the target "damps out before another un-desired peak, a
eardrum of moving coil designs using methods described change in one or more insert earphone components may be
herein to achieve high accuracy frequency responses. necessary. If an undesired peak is moved from 4 kHZ down to
FIG. 3 illustrates an exemplary graph of a response at the 3 kHz, for example, the diameter of the front sound channel
eardrum of a concha mounted or partially/full sealing unit 522A and/or the diameter of the sound channel 526A may be
currently on the market compared to the average human ear 25 reduced. In this regard, damping elements 524A and/or 530A
response as seen in FIG. 1. may be used to Smooth out the frequency response of the
FIG. 4 illustrates an exemplary graph of a response at the insert earphone 500A.
eardrum of a concha mounted or partially/full sealing unit In another embodiment of the invention, the damping ele
currently on the market compared to the average human ear ment 524A may be mounted to a removable plug 520A as a
response as seen in FIG. 1. FIGS. 3 and 4 demonstrate the 30 means of replacement in instances when the damping element
current state-of-the-art for earphone products that employ 524A becomes clogged with earwax or other contaminants.
moving coil drivers. Damping element 530A may also be attached to the insert
In accordance with an embodiment of the invention, meth element 514A.
ods of modifying insertion responses while obtaining exter In yet another embodiment of the invention, low-frequency
nal noise reduction may include, for example, the use of 35 bass response of the insert earphone 500A may be increased
damping elements, auxiliary Volumes, Sound channels, and/ by the use of a “modified Thuras tube' with regard to the
or electronic components. sealed back auxiliary volume 540A. In this regard, the size of
FIG. 5A is a diagram illustrating exemplary acoustic con the bass boost may be determined, for example, by the relative
struction of a high accuracy moving coil design for an insert values of the diaphragm compliance and the Volume of the
earphone assembly with a complete form factor designed to 40 auxiliary back volume 540A. The frequency at which the bass
fit deeply into the ear canal of a user, in accordance with an boost begins may be determined by the resistance and iner
embodiment of the invention. Referring to FIG.5A, the insert tance, or acoustic mass, of the connecting tube 542A and/or
earphone 500A may comprise a cap 502A, a body 503A, a 536A, or the resistance of the damper538A and/or 544A. The
moving coil driver 510A, a diaphragm 512A, an insert ele rate of rise of the low-frequency bass response may increase
ment 514A, a plug 520A, and an eartip. 518A. In addition, the 45 with the use of inertance. Such "modified Thuras tube'
insert earphone 500A may comprise damping elements method of using a filter?bypass circuit within the insert ear
506A, 524A, 530A, 534A, 535A, 538A, and 544A which phone 500A may be used to increase the low frequency sen
may be used with sound channels 504A, 522A, 526A, 532A, sitivity without changing the high-frequency sensitivity. In
513A, 536A, and 542A, respectively. The damping elements this regard, the insert earphone 500A may be used as a means
506A, 524A, 530A, 534A, 535A, 538A, and 544A may also 50 of bass compensation for devices such as MP3 players, for
be used in connection with auxiliary volumes 508A, 528A, example, with output impedance that may be higher for low
537A, and 540A, as well as with diaphragm 512A. These frequencies, thereby delivering less bass energy to the ear
acoustic combinations may also be aided by use of electronic phone as compared to devices with constant output imped
components, such as the electronic filter illustrated in FIG.5C ance through the audio frequency band.
and/or the electronic filter?bypass circuit illustrated in FIG. 55 FIG. 5B is a diagram illustrating exemplary acoustic con
SD. struction of a high accuracy moving coil design for an insert
The insert earphone 500A, whose natural resonance may earphone assembly with a complete form factor designed to
be at 4 kHZ, may be tuned by these means so that a resonant fit deeply into the ear canal of a user, in accordance with an
peak may occurator around 2.7 kHz, for example, which may embodiment of the invention. Referring to FIG. 5B, the insert
be approximately 12 dB higher in level than measured at 500 60 earphone 500B is similar to the insert earphone 500A of FIG.
HZ. The frequency response may then roll off at approxi 5A. However, the insert earphone 500B comprises an integral
mately 3 dB/octave. The insert earphone 500A may be body 502B. In this regard, the insert element 514A of insert
adapted for deep insertion in the ear canal of a user to achieve earphone 500A may be integrated with the body 503A. Aux
high levels of external noise reduction. Deep insertion of the iliary volume 508B and auxiliary damping element 510B of
earphone 500A may be enabled by a slender form factor so 65 insert earphone 500B may correspond to auxiliary volume
that 20 dB or more of external noise isolation may beachieved 528A and auxiliary damping element 534A, respectively, of
by the earphone 500A. insert earphone 500A. Additionally, the auxiliary duct 506B
 US 8,649,546 B2
5 6
may be disposed within a removable plug 504B, thereby embodiment of the present invention. Referring to FIG.5G,
making optional the use of the auxiliary duct 506B and the the passive electrical filter may comprise resistors 502c,508c,
auxiliary volume 508B. and 510c, capacitors 504c and 512c. Inductor 506c may be
FIG.5C is a diagram illustrating an insert earphone assem functionally equivalent and may indicate a moving coil
bly using one or more acoustic resonant ducts, in accordance driver. The passive electrical filter may be used in connection
with an embodiment of the invention. Referring to FIGS. 5A with an insert earphone, such as the insert earphone 500A of
and 5C, in one embodiment of the invention, a resonant duct FIG. 5A, to vary the frequency response of the insert ear
502C may be utilized by the insert earphone 500A. In this phone. In one embodiment of the invention, the electrical
regard, by utilizing the resonant duct 502C, a deficiency in the filter may be implemented within the insert earphone 500A
response may be increased and excess energy in another 10 and filtering may be triggered automatically or upon an input
frequency band may be simultaneously reduced. Therefore, from a user of the insert earphone 500A. Even though one
by adding the resonant duct 502C to the main sound channel implementation of a passive electrical filter is disclosed in
526A, the frequency response of the insert earphone may be FIG.5G, the present invention may not be so limited and other
improved. filter implementations may also be used in connection with an
The resonant duct 502C may extend from the main sound 15 insert earphone such as the insert earphone 500A in FIG. 5A.
channel 526A and may be tuned to have, for example, a /4 FIG.5H is a schematic diagram of an exemplary electrical
wave anti-resonance at 10 kHz. In this regard, the acoustic filter?bypass circuit 606 for modifying bass response, which
tube and the resulting anti-resonance effect may be utilized to may be used in accordance with an embodiment of the inven
decrease and/or prevent excess energy which may be present tion. Referring to FIG.5H, the filter circuit 606 may comprise
within the insert earphone 500A. Furthermore, by utilizing a resistor R1, a capacitor C1 and a switch SW1. In one
the resonant duct 502C in connection with the side cavity embodiment of the invention, the filter circuit 606 may com
528A and the auxiliary damper 535A may result in reduction prise a high-pass filter. Furthermore, the filter circuit 606 may
of excessive energy at 10 kHZ, as well as an increase of a be coupled to a moving coil driver, Such as the moving coil
deficiency in the frequency response from 4 kHz to 8 kHz. driver 510A in FIG. 5A. The electrical filter circuit 606 may
Consequently, the use of the resonant duct 502C within the 25 be used within an insert earphone, such as the insert earphone
insert earphone 500A may result in a smoother and accurate 500A in FIG. 5A, to select between a flat bass response,
frequency response. represented by graph 604, and a boosted bass response, rep
FIG. 5D illustrates exemplary graphs of frequency resented by graph 602.
responses of an insert earphone assembly using one or more A boosted bass response 602 may be obtained when the
resonant ducts, in accordance with an embodiment of the 30 R1-C1 filter circuit is bypassed when the switch SW1 is
invention. Referring to FIG. 5D, graph. 504D may represent switched to the Low Frequency Boost (LFB) position. The
exemplary frequency response of the insert earphone 500A flat bass response 604 may be obtained within the insert
using side cavity 528A with the auxiliary damper 535A and earphone 500A when the switch SW1 is switched to the “flat”
without additional acoustic Volume. Such as resonant duct position. Resistance and capacitance R1 and C1 may be
502C. Graph. 502D may represent exemplary frequency 35 selected to correspond to the impedance of the moving coil
response of the insert earphone 500A using side cavity 528A, driver 510A, for example.
auxiliary damper 535A and the additional resonant duct 502C In one embodiment of the invention, the electrical filter/
for achieving an anti-resonance effect. In this regard, it may bypass circuit 606 may be implemented within the insert
be noted from graphs 502D and 504D that a smoother down earphone 500A and filtering may be triggered automatically
ward slope of the frequency response may begin at about 2 40 or upon an input from a user of the insert earphone 500A and
kHz up to about 16 kHz, for example. a corresponding change in the position of switch SW1. Even
FIG.5E is a diagram illustrating an insert earphone assem though one implementation of the electrical filter circuit 606
bly using one or more resonant ducts, in accordance with an is disclosed in FIG. 5H, the present invention may not be so
embodiment of the invention. Referring to FIG. 5E, there is limited and other filter implementations may also be used in
illustrated the insert element 514A which is a part of the insert 45 connection with an insert earphone such as the insert ear
earphone assembly 500A of FIG. 5A. In one embodiment of phone 500A in FIG. 5A. By using the electrical filter?bypass
the invention, the insert element 514A may comprise a reso circuit 606 within the insert earphone 500A, a bass boost may
nant duct (RD) 502E. The RD 502E may comprise the reso be provided with fixed high-frequency gain without using a
nant duct 502C of FIG. 5C, and may comprise one or more shunt capacitor. Bass boost may be achieved by, for example,
interconnected Volume portions of varying lengths. Further 50 utilizing a “modified Thuras tube” method, as described
more, the RD 502E may extend from the main sound channel herein.
526A and may be tuned to have, for example, a /4 wave FIG. 5I is a graph illustrating the effect of an exemplary
anti-resonance at about 10 kHz, as explained herein above high pass filter for shaping the response of an insert earphone,
with regard to the resonant duct 502C. in accordance with an embodiment of the invention. Refer
FIG. 5F is a diagram illustrating a portion of an insert 55 ring to FIGS.5G and 5I, the graph of FIG.5I demonstrates the
earphone assembly using one or more resonant ducts, in effect of a high pass filter where a source may be connected
accordance with an embodiment of the invention. Referring through a resistor 510c parallel with a capacitor 504c. in
to FIG.5F, there is illustrated a diagram of the RD 502E. In series with a driver 506c to ground. The value of the resistance
one embodiment of the invention, the RD502E may comprise 510c may determine the sensitivity of the insert earphone
four interconnected volume portions 502F, ..., 508F. Each of 60 500A for low frequencies. The low frequency impedance, Xc,
the interconnecting volume portions 502F, ..., 508F may be of capacitor 504c may be high and thus resistor 510c may
of varying length, diameter and/or shape. In addition, the dominate and the current flow may remain low to the driver.
volume portions pairs 508F-506F, 506F-504F, and 504F At high frequencies, however, Xc of capacitor 504c may
502F may be connected at varying angles, resulting in the RD become low and may pass more current to the driver 506c.
SO2E. 65 thereby resulting in higher output.
FIG. 5G is a schematic diagram of an exemplary passive FIG. 5J is a graph illustrating the effect of an exemplary
electrical filter, which may be utilized in connection with an high pass filter for shaping the response of an insert earphone,
 US 8,649,546 B2
7 8
in accordance with an embodiment of the invention. Refer embodiment of the invention. An alternate path or additional
ring to FIGS. 5G and 5J, the graph of FIG. 5J illustrates path to auxiliary volume 528A from 532A, 534A is via aux
another example of a high pass filter where capacitor 504c iliary duct 513A and auxiliary damping element 535A. Refer
may remain and resistance 510c may be varied. In this regard, ring to FIGS.5A and 8A, a notch filter effect may beachieved
the low-pass filter in FIG. 5G may be tuned to apply a first with acoustic components in combination to reduce the level
order high frequency response roll-off where desired. in a specific frequency band. For example, the main Sound
FIG. 6 is a graph that illustrates an exemplary response of channel 526A and/or front speaker volume 535A may be
an insert earphone with various levels of damping, in accor varied. In addition, the auxiliary duct 513A and/or 532A
dance with an embodiment of the invention. leading to auxiliary volume 528A, may also be varied. Sound
Depending on the natural behavior of a given moving coil 10 channel 526A and auxiliary duct 513A may comprise any
design, the combination of resonant peak shifting and/or geometric shape that results in the desired frequency
Smoothing may require any range of damping values. If, for response. The depth or “O'” of the notch filter may be limited
example, there are two natural peaks close to the target peak by adding auxiliary damping elements 534A and/or 535A.
frequency, damping may be used to reduce both peaks to the Such notch filter combinations may be duplicated with dif
correct shape. However, if the peak closest to the target hap 15 ferent values and sizes to reduce energy in multiple spectral
pens to "damp out before another un-desired peak, a change ranges.
in front plumbing may be necessary. If an undesired peak is FIG. 8B is a graph that illustrates changes in frequency
moved from 4 kHz, for example, down to 3 kHz, for example, response of an insert earphone utilizing an auxiliary dia
a reduction in front plumbing diameter may be necessary. In phragm, in accordance with an embodiment of the invention.
this regard, peak movement and/or damping may smooth out Undesired peaks in the response may also be reduced by
the response. use of one or more auxiliary diaphragms (512A). In order to
Many moving coil drivers can produce extremely high realize cancellation, the diaphragm(s) must have characteris
sound pressure levels relative to their placement in the ear. In tic impedances that are tuned to change phase relative to the
reference to the insert earphone 500A, a reduced amount of driver diaphragm, within the frequency band of interest. The
power may be required to develop acceptable level of sound 25 unchanged response (AH-13C) may be compared to a
pressure at the eardrum while maintaining desired Sound response incorporating an auxiliary diaphragm (AH-13D).
quality. In one embodiment of the invention, the low fre With one or more auxiliary diaphragms in place, an addi
quency of a moving coil driver may be tuned by changing tional advantage may be realized within the insert earphone
internal capacitance or rear volume (540A and/or 508A). The 500A. Resonant peaks may be directly shifted closer to a
size of the rear Volume may depend on sensitivity and/or 30 target range that may not have been otherwise attainable.
accuracy requirements. A Smaller Volume may reduce the Notch filters as described herein above may also be used to
low-mid frequency response sensitivity. However, the fre enhance the effect of auxiliary diaphragms.
quency response sensitivity of the earphone 500A may be FIG. 9A is a graph illustrating acoustic bass boost, in
regained by electro-acoustic transfer efficiency realized with accordance with an embodiment of the invention.
sealed insert earphone designs of the earphone 500A. 35 FIG.9B is a graph illustrating bass boost, in accordance
FIG. 7 is a graph that illustrates the effect on the frequency with an embodiment of the invention.
response when the sealed rear Volume, Such as the sealed rear In accordance with an embodiment of the invention, Small
volume 540A and/or 508A in FIG. 5A, is varied, in accor scale speakers may be tuned to have an optional Sub-fre
dance with an embodiment of the invention. Referring to quency resonance by venting the rear Volume through a
FIGS. 5A and 7, auxiliary volume 540A may be varied in 40 highly inductive and resistive vent. In this regard, the correct
connection with the auxiliary duct 542A, auxiliary damping band of Sub frequencies may be increased.
element 544A, and auxiliary volume 508A. For example, a boost in a speaker may be tuned to create a
In accordance with an embodiment of the invention, the mild boost (FIG.9A) to correct a shortage of low frequencies
speakers internal capacitance may be reduced by encapsu typically occurring in a “bass adjusted system’ so as to
lating the volume of air around the back of the speaker similar 45 improve overall response accuracy. An additional increase in
to standard enclosed loudspeakers, which may be required for low frequency sensitivity above the reference may serve an
achieving external noise reduction. The size of this rear vol application that requires/desires more bass response (refer to
ume may depend on sensitivity and accuracy requirements. In FIG.9B). Such response adjustments may lower the accuracy
this regard, FIG. 7 demonstrates the effect on the frequency score. A boost in a speaker may be tuned and a mild boost,
response when the sealed rear volume(s) 540A, 508A are 50 such as illustrated in FIG. 9A, may not adversely effect the
varied. In some instances, auxiliary volume 540A may be the overall accuracy.
only volume required in which case auxiliary duct 542A may A method to tune these Small scale speakers to have an
be blocked and auxiliary damping element 544A may not be optional Sub-frequency resonance can be accomplished when
used. rear speaker auxiliary duct 536A, vents either through auxil
In some instances, resonant peaks may be present, result 55 iary damping element 538A or directly into auxiliary volume
ing in detraction from the listening experience. In one 540A, which may be blocked at auxiliary duct 542A. If a
embodiment of the invention, the resonant peaks may be larger rear Volume is required, any combination of auxiliary
smoothed out by tuning of the front port 522A, 526A and/or damping elements 538A, 544A, and/or 506A may be used in
by application of acoustic resistance 524A, 530A. In some conjunction with auxiliary ducts 536A, 542A, and/or 504A
instances it may be necessary to augment Such remedial 60 that vent into either or both auxiliary volumes 540A and
methods by incorporation of one or more series of inertance SO8A.
532A resistance 534A tanks terminated by an acoustic In this regard, the correct band of Sub frequencies may be
capacitance 528A in the front acoustic path of the earphone increased. For example, a speaker may be tuned to create a
500A. Such structure may create a notch filter aimed at reduc mild boost to correct a shortage of low frequencies typically
ing the intensity of the undesired spectral energy. 65 occurring in a “bass adjusted system'. An additional increase
FIG. 8A is a graph that illustrates a varied notch filter and in low frequency sensitivity may serve an application that
its effect on frequency response, in accordance with an requires/desires more bass response (refer to FIG.9A). FIG.
 US 8,649,546 B2
10
9B demonstrates an extreme adjustment to the bass frequen absorb sound from said main Sound channel to reduce a
cies. The resulting Sound quality may be characterized as level in a specific frequency band of said insert earphone
“tubby” or undesirable. assembly.
Accordingly, aspects of the invention may be realized in 2. The assembly of claim 1 further comprising a main
hardware, software, firmware or a combination thereof. The 5 damping element in connection with said main sound channel
invention may be realized in a centralized fashion in at least adapted to reduce at least one natural peak that is close to a
one computer system or in a distributed fashion where differ target peak frequency.
ent elements are spread across several interconnected com 3. The assembly of claim 2 wherein a diameter of said main
puter systems. Any kind of computer system or other appa Sound channel may be reduced if the at least one natural peak
ratus adapted for carrying out the methods described herein is 10
damps out.
Suited. A typical combination of hardware, Software and firm 4. The assembly of claim 2 wherein the main damping
ware may be a general-purpose computer system with a com element is mounted to at least one of
puter program that, when being loaded and executed, controls
the computer system such that it carries out the methods a removable plug, and
described herein. 15 an insert element,
The present invention may also be embedded in a computer to enable replacement of the main damping element if the
program product, which comprises all the features enabling main damping element becomes clogged.
the implementation of the methods described herein, and 5. The assembly of claim 1 wherein said transducer com
which when loaded in a computer system is able to carry out prises a moving coil driver.
these methods. Computer program in the present context may 6. The assembly of claim 5 wherein said insert earphone
mean, for example, any expression, in any language, code or using a moving coil driver results in an accuracy score of at
notation, of a set of instructions intended to cause a system least 80 percent.
having an information processing capability to perform a 7. The assembly of claim 1 further comprising a removable
particular function either directly or after either or both of the auxiliary duct plug for disposing one of the at least one
following: a) conversion to another language, code or nota 25 auxiliary duct and one of the at least one auxiliary volume.
tion; b) reproduction in a different material form. However, 8. The assembly of claim 1 further comprising at least one
other meanings of computer program within the understand electronic componentadapted to modify at least one insertion
ing of those skilled in the art are also contemplated by the response.
present invention. 9. The assembly of claim 8 wherein the at least one elec
While the invention has been described with reference to 30 tronic component is a passive electrical filter for varying a
certain embodiments, it will be understood by those skilled in frequency response of the insert earphone.
the art that various changes may be made and equivalents may 10. The assembly of claim 8 wherein the at least one elec
be substituted without departing from the scope of the present tronic component is an electrical filter/bypass circuit for
invention. In addition, many modifications may be made to modifying a bass response.
adapt a particular situation or material to the teachings of the 35 11. The assembly of claim 10 wherein the electrical filter/
present invention without departing from its scope. There bypass circuit selects one of:
fore, it is intended that the present invention not be limited to a flat bass response, and
the particular embodiments disclosed, but that the present a boosted bass response.
invention will include all embodiments falling within the 12. The assembly of claim 10 wherein the electrical filter/
Scope of the appended claims. 40 bypass circuit uses a modified Thuras tube.
What is claimed is: 13. The assembly of claim 1 wherein said transducer is a
1. An insert earphone assembly, comprising: balanced armature driver.
a transducer adapted to convert electrical signals into 14. The assembly of claim 1 wherein the insert earphone is
Sound energy: a sealed insert earphone design for reducing an external noise.
a main Sound channel adapted to communicate said Sound 45 15. The assembly of claim 1 further comprising at least one
energy to a user, and auxiliary diaphragm for reducing at least one peak in at least
at least one auxiliary Volume connected to said main Sound one insertion response.
channel via at least one auxiliary damping element and 16. The assembly of claim 15 wherein at least one notch
at least one auxiliary duct, wherein the at least one filter is used with the at least one auxiliary diaphragm to
auxiliary Volume, the at least one auxiliary damping 50 further reduce the at least one peak.
element, and the at least one auxiliary duct are adapted to k k k k k