Court Opinion

ID: 4127096
Source: CourtListenerOpinion
Date Created: 2017-02-17 16:01:13.994537+00
Date Added: 2024-06-11T07:46:25.324006
License: Public Domain

NOTE: This disposition is nonprecedential.

  United States Court of Appeals
      for the Federal Circuit
                ______________________

     SLOT SPEAKER TECHNOLOGIES, INC.,
                 Appellant

                           v.

                     APPLE INC.,
                    Cross-Appellant
                ______________________

                 2015-2038, 2015-2039
                ______________________

   Appeals from the United States Patent and Trade-
mark Office, Patent Trial and Appeal Board in No.
IPR2014-00235.
               ______________________

              Decided: February 17, 2017
               ______________________

   KENNETH J. HALPERN, Perkins Coie, LLP, Palo Alto,
CA, argued for appellant. Also represented by ERIC L.
WESENBERG, CHRISTOPHER LEE KELLEY.

    MARK CHRISTOPHER FLEMING, Wilmer Cutler Picker-
ing Hale and Dorr LLP, Boston, MA, argued for cross-
appellant. Also represented by BRYAN S. CONLEY, KEVIN
GOLDMAN; NINA S. TALLON, DAVID LANGDON CAVANAUGH,
Washington, DC; NATALIE POUS, New York, NY.
                  ______________________
2                 SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.

    Before LOURIE, DYK, and O’MALLEY, Circuit Judges.
O’MALLEY, Circuit Judge.
    Appellee/Cross-Appellant Apple Inc. (“Apple”) filed a
petition for inter partes review of various claims of U.S.
Patent No. 7,433,483 (“the ’483 patent”), assigned to
Appellant/Cross-Appellee Slot Speaker Technologies, Inc. 1
(“Slot Speaker”). The Patent Trial and Appeal Board
(“the Board”) instituted review on claims 1–3 of the ’483
patent, and concluded that claims 1 and 2 would have
been obvious over prior art, but claim 3 would not have
been obvious. Apple Inc. v. THX Ltd., IPR2014-00235,
2015 WL 3638275 (P.T.A.B. June 9, 2015) (“Board Deci-
sion”). Slot Speaker appeals the Board’s decision on
claims 1 and 2; Apple cross-appeals the Board’s decision
on claim 3. We conclude that substantial evidence sup-
ports the Board’s finding that claims 1 and 2 of the ’483
patent would have been obvious. We conclude that the
Board erred, however, in ruling that claim 3 of the ’483
patent would not have been obvious. We therefore affirm-
in-part and reverse-in-part.
                     I. BACKGROUND
                   A. The ’483 Patent
    The ’483 patent is directed to a sound reproduction
system with a speaker configuration providing a “relative-
ly narrow sound output region in relation to the size of
the speaker face(s) utilized in the sound reproduction
system.” ’483 patent, col. 3 ll. 22–26. Figures 1 and 2B of
the ’483 patent, shown below, depict the configuration of
the speaker and sound duct walls. The speaker 107 is
mounted perpendicular to the sound duct 115, such that

    1 Slot Speaker Technologies, Inc. was formerly
known as THX, Ltd.
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.               3

sound is redirected from the speaker, through the sound
duct, and exits an output aperture 106. The duct wall
103 opposite the speaker has a sound reflecting surface,
while sound damping material is added to the sidewalls
104 and 105 and the back wall 112.

Id. figs. 1–2.
     The sound damping material reduces standing waves
inside the duct. Standing waves occur when sound is
trapped between opposite reflecting walls, at frequencies
where the distance between the walls is an integer num-
ber of half-wavelengths. These unwanted resonances
diminish the quality of the projected sound. Because the
speaker is narrow vertically, standing waves do not form
in the vertical direction and, thus, sound damping mate-
rial is not required on the top and bottom surfaces. The
’483 patent teaches the elimination of standing waves in
the horizontal direction by placing sound damping mate-
rial on the sidewalls and back wall of the sound duct. Id.
col. 8, ll. 17–28.
    The Board instituted review on claims 1–3 of the ’483
patent. Claim 1 of the ’483 patent recites:
    A narrow profile sound system, comprising:
    a drive unit disposed on a mounting surface, said
    mounting surface forming a barrier acoustically
    isolating the drive unit’s forward radiation from
    its rearward radiation;
4                     SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.

    a sound reflecting surface facing the drive unit
    and substantially parallel with the mounting sur-
    face; and
    sound damping material disposed between said
    sound reflecting surface and the mounting sur-
    face, the sound reflecting surface and the mount-
    ing surface defining a bottom and top of a narrow
    sound duct terminating in an elongate output slot,
    with the sound damping material forming the
    sides of the sound duct, whereby forward radia-
    tion from the drive unit is turned at a substantial-
    ly right angle and channeled along a straight path
    towards the output slot;
    wherein the sound damping material forms an
    outer shape of the sound duct which reduces
    sound reflections at the end of the sound duct op-
    posite the output slot and thereby mitigates
    standing waves.
Id. col. 29, l. 62–col. 30, l. 13.
    Claim 2 depends from claim 1, adding the limitation
that “sound emanating from the output slot is character-
ized by a wide horizontal dispersion angle and a narrow
vertical dispersion angle, as a result of the elongate shape
of the output slot.” Id. col. 30, ll. 14–19.
     Claim 3 depends from claim 1 and includes the addi-
tional limitation that the “sound damping material forms
a back wall of the sound duct, said back wall substantially
following a curved contour of a portion of a drive unit cone
farthest opposite from the output slot.” Id. col. 30, ll. 20–
33.
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.                  5

                       B. Prior Art
    The Board instituted based on three prior art refer-
ences; two are relevant to this appeal. 2
                       1. Tomonori
    Tomonori et al., EP 0744880 A1 (“Tomonori”), disclos-
es a speaker mounted perpendicular to a sound duct, such
that sound from the speaker is directed through the duct
and exits a narrow aperture positioned along the side of
the television screen, as shown below.

    2    The Board instituted based in part on U.S. Patent
No. 3,687,220 (“Virva” or “the ’220 patent”), which de-
scribes a speaker system that augments the bass-range
response of two small speakers by using a serpentine
enclosure behind the drive units to create a tuned air
column. Virva teaches that “all inside surfaces of the
enclosure should be treated with acoustically absorbing
material to prevent spurious resonances or standing
waves from developing within in the enclosure.” ’220
patent, col. 3, ll. 42–46. In its Final Written Decision, the
Board found that a person of ordinary skill in the art
would not have utilized the disclosure of Virva in modify-
ing Tomonori. No party appeals that aspect of the deci-
sion, so we do not address this reference further.
6                  SLOT SPEAKER TECHNOLOGIES     v. APPLE INC.

Tomonori, figs. 1, 7. Tomonori recognizes that one of the
problems of directing sound through a duct is the pres-
ence of “standing waves.” Id. col. 2, ll. 12–18. Tomonori
describes that standing waves are produced when “some
of the sound waves are reflected owing to a marked
change in the acoustic impedance at the tube open end
and return toward the speaker 12 to produce standing
waves.” Id. col. 2, ll. 46–49. Standing waves create
resonant frequencies that interfere with other sound-
waves and degrade the quality of sound leaving the sound
duct.
    To eliminate the formation of standing waves,
Tomonori provides two solutions. First, Tomonori locates
the speaker at an “anti-node,” one-third to one-fifth of the
distance of the total length of the sound tube from its
closed back end. Id. col. 2, ll. 45–50. Figure 16 illustrates
this configuration.

Id. fig. 16. Second, Tomonori teaches that the duct should
be “internally provided with a sound absorbing materi-
al . . . adapted to absorb standing waves.” Id. col. 1, l. 57–
col. 2, l. 5. To this end, Tomonori discloses adding sound
absorbing material to the back wall of the sound duct. By
absorbing and eliminating the standing waves, Tomonori
teaches that the sound quality is improved. Id. col. 8, ll.
19–25.
                         2. Sadaie
    Sadaie et al., WO Pub. No. 00/52958 (“Sadaie”), dis-
closes a small-sized speaker system with a narrow-profile
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.              7

configuration and a speaker driver positioned perpendicu-
lar to a sound duct. Sadaie’s speaker system is designed
to enhance speaker response at the low end of the fre-
quency spectrum. Sadaie teaches that the sidewalls and
back wall of the sound duct may be lined with two differ-
ent layers, “pressure absorbing material” and “acoustic
material,” which both shapes the path through which
sound travels and regulates pressure and unwanted noise
inside the duct. J.A. 581–82.
    As depicted in Figure 17 (side view, below left), the
speaker driver 11 is mounted inside an enclosure 10. As
shown in the overhead view in Figure 18 (below right),
sound travels from the speaker driver through a sound
duct referred to as a “sound guiding part 40.” The sound
duct, or sound guiding part, has two sections: a “sound
source space 41” that encompasses the area beneath the
speaker driver, and a “sound path 42” that extends from
the sound source space to the output aperture 45.

Sadaie, figs. 17–18; J.A. 609–10. The top wall of the
Sadaie sound duct is formed by the speaker enclosure, the
bottom wall is referred to as the “wall body 50”, and an
“intermediate member 30” forms the sidewalls and back
wall. Sadaie teaches that some or all of the wall surface
may be covered with a “pressure absorbing material 31”
to define the shape of the sound duct. As seen in Figure
18, pressure absorbing material may be added to the
surface of the intermediate member to create a sound
path with curved walls.
8                  SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.

    This pressure absorbing material is added to “enable[]
control of the bass reproduction capability, output charac-
teristics, noise, wind noise, and the like of the obtained
speaker system.” J.A. 582. The pressure absorbing
material “does not require sound absorbency but may
have sound absorbency.” J.A. 582. Sadaie teaches that
sound absorbency is particularly beneficial to “improve
sound quality” when it is used to reduce high frequency
sounds like wind noise. J.A. 582.
    Sadaie teaches that the pressure absorbing material
may be further padded with an “acoustic material 32.”
Like the pressure absorbing material, the acoustic mate-
rial “does not require sound absorbency but may have
sound absorbency.” J.A. 583. In the preferred embodi-
ment, the acoustic material is a sound damping material
such as a felt or soft film. J.A. 583. Sadaie explains that
the acoustic material “may be provided on an entire
surface of the wall surface of the sound guiding part” or it
“may be disposed on any appropriate position on the wall
surface according to the purpose.” J.A. 582.
                  C. Procedural History
    Slot Speaker sued Apple in the Northern District of
California, alleging infringement of U.S. Patent No.
8,457,340 (“the ’340 patent”), which shares a common
specification with the ’483 patent. Thereafter, Apple filed
(1) a petition for inter partes review of claims 1–6, 8, 10,
and 18–20 of the ’483 patent, and (2) a petition requesting
inter partes review of claims 1–7 and 29–34 of the ’340
patent. The Board instituted inter partes review on
claims 1–3 of the ’483 patent, but declined to institute
inter partes review on any claim of the ’340 patent. The
parties stipulated to a stay of the civil proceedings.
    The Board issued its Final Written Decision on the
patentability of the ’483 patent on June 9, 2015, deter-
mining that claims 1 and 2 would have been obvious over
Tomonori in view of Sadaie, but that claim 3 would not
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.                  9

have been obvious. Board Decision, 2015 WL 3638275, at
*2. Both parties appealed from those respective aspects of
the Board’s decision which were adverse to them. We
have jurisdiction over Slot Speaker’s appeal and Apple’s
cross-appeal under 35 U.S.C. §§ 141(c), 319 and 28 U.S.C.
§ 1295(a)(4)(A).
                 II. STANDARD OF REVIEW
    Obviousness is a question of law based on underlying
factual findings, including the scope and content of prior
art references and the existence of a reason to combine
those references. In re Hyon, 679 F.3d 1363, 1365–66
(Fed. Cir. 2012). We uphold the Board’s factual findings
unless they are not supported by substantial evidence,
while we review the Board’s legal conclusions de novo.
Dynamic Drinkware, LLC v. Nat’l Graphics, Inc., 800 F.3d
1375, 1378 (Fed. Cir. 2015). A finding is supported by
substantial evidence if a reasonable mind might accept
the evidence to support the finding. In re Jolley, 308 F.3d
1317, 1320 (Fed. Cir. 2002).
                      III. DISCUSSION
            A. Obviousness of Claims 1 and 2
     Slot Speaker appeals the Board’s determination that
claims 1 and 2 of the ’483 patent would have been obvious
over Tomonori in light of Sadaie. Neither party challeng-
es the Board’s claim construction of the term “sound
reflecting surface”: “a surface that redirects sound waves
output from a speaker, not made of sound damping mate-
rial.” Board Decision, 2015 WL 3638275, at *4–7. Under
this construction, the Board found that Tomonori disclos-
es every limitation of claim 1 of the ’483 patent, except for
“sound damping material forming sides of the sound
duct.” Id. at *8–10.
    Sound damping material is used in the ’483 patent on
the sidewalls and optionally the back wall of the sound
duct, but not on the top or bottom surfaces. This configu-
10                 SLOT SPEAKER TECHNOLOGIES    v. APPLE INC.

ration prevents “expansion of the sound waves in a rear-
ward direction, [] thereby reducing potential interference
or other undesirable acoustic effects.” ’483 patent, col. 22,
l. 64–col. 23, l. 3. Claim 1 further specifies that “sound
damping material forms an outer shape of the sound duct
which reduces sound reflections at the end of the sound
duct opposite the output slot and thereby mitigates stand-
ing waves.” Id. col. 30 ll. 10–13. The Board determined
that the sound damping material Tomonori discloses at
the closed end of its sound tube “fulfills the same function
disclosed in the ’483 patent even though it does not form
the sides of the sound duct.” Board Decision, 2015 WL
3638275, at *12.
     The Board then analyzed whether one of ordinary
skill in the art would have been motivated to combine
Sadaie with Tomonori to use sound damping material to
form the sides of Tomonori’s sound duct. The Board
concluded that Sadaie shows that the use of sound damp-
ing material along the sides of a sound duct is “a known
configuration to suppress standing waves inside a duct.”
Id. Apple’s expert Dr. Vipperman explained that Sadaie
used a sidewall sound damping method to enable “the
sharpness of a fundamental wave resonance of a standing
wave determined by the length of the sound path . . . to be
suppressed because a substantial length of the sound path
cannot be primarily determined.” J.A. 530. The Board
found that “[e]xtending the damping material of Tomonori
along the sidewalls of the duct, as taught by Sadaie,
would have been one of a limited number of known solu-
tions further minimizing the presence of spurious reso-
nances and standing waves inside the duct.” Board
Decision, 2015 WL 3638275, at *12 (quotation omitted).
In light of Sadaie’s teachings, the Board found that a
person of ordinary skill in the art would have been moti-
vated to modify Tomonori by using sound damping mate-
rial along the sides of the narrow sound duct.
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.                11

    Slot Speaker disputes the Board’s use of Sadaie to
disclose the extension of sound damping material along
the sidewalls of the duct. We conclude, however, that
substantial evidence supports the Board’s findings that
(1) Sadaie discloses the extension of sound damping
material along the sidewalls of the duct, and (2) there is a
sufficient teaching or motivation to combine Sadaie and
Tomonori.
    The plain language of Sadaie discloses the extension
of sound damping material along the sidewalls of the
duct. Sadaie teaches that the wall surface (the surface of
the intermediate member) may be “pressure absorbing
material” and an “acoustic material,” and that “[t]he
pressure absorbing material does not require sound
absorbency but may have sound absorbency,” and in the
preferred embodiment, the pressure absorbing material is
a sound damping material such as foam. J.A. 582. The
acoustic material “does not require sound absorbency but
may have sound absorbency,” and, in the preferred em-
bodiment, the acoustic material is a sound damping
material such as felt. J.A. 583. Sadaie teaches that the
pressure absorbing material and acoustic material may
extend along the sidewalls from the area near the speaker
to the output aperture.
     Sadaie further teaches that pressure absorbing mate-
rial can be used to mitigate standing waves:
   [T]he pressure absorbing material in the defined
   section 31 enables the sharpness of a fundamental
   wave resonance of a standing wave determined by
   the length of the sound path 42 to be suppressed
   because a substantial length of the sound path
   cannot be primarily determined.
J.A. 584. The pressure absorbing material of Sadaie may
absorb both pressure and sound from the standing wave.
Sadaie explains that “the pressure absorbing material in
combination with the acoustic material allows the slight
12                  SLOT SPEAKER TECHNOLOGIES     v. APPLE INC.

sound absorption that exists in the pressure absorbing
material (for example, urethane foam) in the bass range
to be nearly zero, thereby further suppressing the energy
loss in the bass range.” J.A. 583. Given these teachings,
we conclude that the Board did not commit error when it
referred to Sadaie’s mitigation of standing waves with
sound damping material, rather than pressure absorbing
material.
    We also conclude that substantial evidence supports
the Board’s determination that Sadaie teaches sidewall-
only placement of the sound damping material. In fact,
Slot Speaker’s counsel conceded during the oral hearing
before the Board that Sadaie does not only teach the
placement of sound absorbing material on all sides of the
duct:
     JUDGE MURPHY: I mean, if we only focus on
     the structure, Sadaie -- even in the paragraph
     that you have reproduced for us on slide 28, bot-
     tom of page 12 of Sadaie, it indicates that the
     sound absorbing material, which is in that pres-
     sure adjustment section 32, which is described as
     felt or a thin film of some sort, or soft film in Sa-
     daie, it may be only on the wall surface of one side
     of the sound path, so that's one side of a sound
     duct. It could be one side. It could be two sides.
     It could be all sides. It's not only all sides, right?
     MR. KELLEY: It is not only all sides, you're cor-
     rect.
J.A. 373 ll. 2–13 (emphasis added). Slot Speaker implicit-
ly concedes that Sadaie teaches sidewall-only placement,
because Slot Speaker reads Sadaie as allowing the
“placement of pressure absorbing material with a sound
absorbing surface ‘on any appropriate position on the wall
surface according to the purpose.’” Slot Speaker Opening
Br. at 57 (quoting J.A. 582).
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.                13

    Despite this concession, Slot Speaker argues that
sidewall-only placement is a species within the genus of
placement of sound absorbing material on any appropri-
ate position of the wall surface. We disagree with Slot
Speaker’s interpretation of the surfaces on which sound
damping material can be placed. Sadaie distinguishes
between the intermediate member surface (sidewalls and
back wall), the “wall body” surface (the bottom wall
opposite the speaker), and the speaker enclosure (the top
wall that holds the speaker driver). Sadaie teaches that
pressure absorbing material and acoustic material are
placed on the intermediate member.         J.A. 581–83;
J.A. 808–11 (¶¶ 22–26). Sadaie further discloses particu-
lar embodiments, claims 9 and 19, where sound absorbing
material is placed only along the intermediate member.
J.A. 594; J.A. 596. We therefore conclude that Sadaie
teaches the placement of two different types of sound
damping material on its sidewalls and back wall, not its
top wall or bottom wall. 3
    Having concluded that Tomonori and Sadaie teach all
of the elements of claim 1, we turn to whether substantial
evidence supports the Board’s finding of a teaching or
motivation to combine these references. “An invention is
not obvious just ‘because all of the elements that comprise
the invention were known in the prior art;’ rather a
finding of obviousness at the time of invention requires a
‘plausible rational [sic] as to why the prior art references

   3    Slot Speaker failed to raise the argument below
that placing the pressure absorbing material of Sadaie in
Tomonori’s duct would eliminate the “straight path”
limitation recited in claim 1 of the ’483 patent. Even if
raised, moreover, we would reject its implications because
Tomonori discloses a straight duct; Sadaie, accordingly,
need not disclose a straight duct in order to reach the
conclusion that claims 1 and 2 were obvious.
14                SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.

would have worked together.’” Broadcom Corp. v. Emulex
Corp., 732 F.3d 1325, 1335 (Fed. Cir. 2013) (quoting
Power-One, Inc. v. Artesyn Techs., Inc. 599 F.3d 1343,
1351 (Fed. Cir. 2010)). “An obviousness determination
requires that a skilled artisan would have perceived a
reasonable expectation of success in making the invention
in light of the prior art.” Amgen Inc. v. F. Hoffman-La
Roche Ltd., 580 F.3d 1340, 1362 (Fed. Cir. 2009) (citation
omitted).
    The Board did not conclude that a person of ordinary
skill in the art simply would have substituted Sadaie into
Tomonori. Instead, the Board found that such a person
would have recognized, based on the teachings of Sadaie,
that the sound damping material along Tomonori’s back
wall could be extended along Tomonori’s sidewalls to
suppress unwanted soundwaves. Board Decision, 2015
WL 3638275, at *12–13.
    Slot Speaker attempts to reframe “success” in this in-
quiry as the production of full-range sound, which Slot
Speaker contends would be impossible through the com-
bination of Tomonori and Sadaie, given that Sadaie
focuses on the production of low frequency bass sounds.
We agree with the Board, however, that the ’483 patent
claims do not require absorption of specific resonances at
specific frequencies, nor any specific threshold with
respect to signal loss. They merely require sound damp-
ing material on the sidewalls, and material that absorbs
any type of sound satisfies the “sound damping material”
element. Id.
    The relevant inquiry is whether a person of ordinary
skill in the art would have had a reasonable expectation
of success in modifying Tomonori in light of Sadaie to
absorb unwanted soundwaves. It is irrelevant whether
Tomonori and Sadaie together would be less effective than
Sadaie alone at avoiding the absorption of certain low
frequencies. See, e.g., In re Kahn, 441 F.3d 977, 990 (Fed.
SLOT SPEAKER TECHNOLOGIES     v. APPLE INC.                  15

Cir. 2006). And Slot Speaker’s argument that Tomonori
and Sadaie are incompatible because they are directed to
different goals fails because a person of ordinary skill
would not have ignored Sadaie’s teachings on the use of
sound damping materials on its sidewalls to absorb un-
wanted soundwaves just because Sadaie discloses that its
material also absorbs pressure. KSR Int’l Co. v. Teleflex
Inc., 550 U.S. 398, 420 (2007) (“[A]ny need or problem
known in the field of endeavor at the time of invention
and addressed by the patent can provide a reason for
combining the elements in the manner claimed.”).
     To this effect, Tomonori and Sadaie both disclose mul-
tiple configurations for sound ducts. Tomonori also dis-
cusses that the use of sound absorbing material was a
known solution to suppress standing waves. Tomonori,
col. 1, l. 57–col. 2 l. 3. Sadaie also discloses that the use of
sound absorbing material along the sides of a sound duct
was a known configuration to suppress unwanted sound-
waves. J.A. 582. Finally, Apple’s expert Dr. Vipperman
explained that the addition of Sadaie’s sidewall-only
sound damping material would be a routine design choice,
as “one of a limited number of known solutions to mini-
mize the presence of standing waves and other unwanted
soundwaves inside the duct.” J.A. 531. Based on this
showing, we conclude that substantial evidence supports
the Board’s finding that a person of ordinary skill in the
art would have recognized that Sadaie’s sidewall-only
placement of sound damping material suppresses stand-
ing waves.
    On dependent claim 2, the Board found that Tomonori
disclosed “an elongate output slot and emit[ted] sound
characterized by a wide horizontal dispersion angle and a
narrow vertical dispersion angle as a result of the elon-
gate output slot.” Board Decision, 2015 WL 3638275, at
*14. Given that claim 2 adds the additional limitation
“wherein sound emanating from the output slot is charac-
terized by a wide horizontal dispersion angle and a nar-
16                 SLOT SPEAKER TECHNOLOGIES    v. APPLE INC.

row vertical dispersion angle as a result of the elongate
output slot,” ’483 patent, col. 30, ll. 14–19, the Board
concluded that Apple had established by a preponderance
of the evidence that the combination of Tomonori and
Sadaie would have rendered claim 2 obvious to a person of
ordinary skill in the art. Because Slot Speaker has not
disputed the Board’s findings with respect to claim 2
specifically, we also affirm the Board’s determination of
obviousness on claim 2.
    For these reasons, we affirm the Board’s determina-
tion that claims 1 and 2 would have been obvious over
Tomonori in view of Sadaie.
                B. Obviousness of Claim 3
    Apple cross-appeals from the Board’s determination
that claim 3 of the ’483 patent would not be rendered
obvious by Tomonori in view of Sadaie. As noted above,
claim 3 adds the additional limitation to claim 1, “wherein
said sound damping material forms a back wall of the
sound duct, said back wall substantially following a
curved contour of a portion of a drive unit cone farthest
opposite from the output slot.” ’483 patent, col. 30, ll. 20–
23. The Board concluded that Tomonori failed to disclose
sound damping material that followed a curved contour of
a portion of the speaker cone farthest opposite the output
slot, as required by claim 3. Board Decision, 2015 WL
3638275, at *15. The Board then concluded that Sadaie’s
pressure/sound damping material (labeled as 31 and 32)
does not follow the curved portion of the speaker cone 21
“farthest opposite from the output slot [45]” to form a
back wall to the sound duct. Id.
    The Board also found that Apple’s expert failed to ex-
plain why a person of ordinary skill in the art would have
relied on Sadaie’s disclosure of a preferred embodiment
where the “sound guiding part [40] has a sound source
space [41] defined according to a peripheral edge portion
of the above speaker unit,” to modify the shape of the
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.               17

sound damping material by following the curved contour
of a speaker cone, as required by claim 3. Id. at *16.
     We first assess whether all of the elements of claim 3
can be found in either Tomonori or Sadaie. We disagree
with the Board’s conclusion that Apple and its expert
failed to identify “any examples in the prior art of sound
damping material forming a back wall of a sound duct
that follows a curved contour of a speaker cone.” Id. at
*15 (emphasis in original). The Board focused its analysis
on Figure 18 of Sadaie to find that the sound damping
material did not follow the curved portion of the speaker
cone farthest opposite from the output slot to form the
back wall. But the claim 3 limitation requires a “back
wall substantially following a curved contour of a portion
of a drive unit cone farthest opposite from the output
slot.” ’483 patent, col. 30, ll. 19–23 (emphasis added).
There is no requirement that the back wall follow the
entire contour of the speaker cone. Sadaie expressly
discloses embodiments where the back wall substantially
follows the curve of the speaker cone farthest opposite the
output slot (in Figures 3 and 4 below). Indeed, the Board
acknowledged that Figure 4 of Sadaie, shown below,
“shows a circular peripheral outer edge of Sadaie’s sound
guide.” Board Decision, 2015 WL 3638275, at *15 n.12.

Sadaie, figs. 3–4; J.A. 599–600.
18                 SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.

    In addition, Sadaie teaches a back wall covered with
sound damping material. Sadaie teaches that the sound
guiding part 40 has two sections: the sound source space
41 encompassing the area beneath the speaker driver;
and a sound path 42 extending from the sound source
space to the output duct 45. These surfaces form the side
and back walls of the duct. Sadaie teaches that:
     [T]he pressure adjustment section 32 may be [1]
     equipped on the entire wall surface of the sound
     path 42, or [2] it may be equipped only on the wall
     surface of one side of the sound path 42, or [3] it
     may be equipped on the wall surface from the
     sound source space 41 to the sound path 42.
J.A. 582–83 (bracketed characters added). As discussed
above, we agree with Apple that Sadaie refers to “pres-
sure adjustment section 32” as containing acoustic mate-
rial. Sadaie further teaches that the acoustic material
may be placed anywhere on the sound guiding part 40:
     The pressure adjustment section 32 may be pro-
     vided on an entire surface of the wall surface of
     the sound guiding part 40. The pressure adjust-
     ment section 32 may be disposed on any appropri-
     ate position on the wall surface according to the
     purpose.
J.A. 582. Thus, Sadaie discloses that the acoustic materi-
al may be placed on the back wall of the sound duct.
    Figure 18, supra, shows Example [1], where the pres-
sure adjustment section is equipped along the entire wall
of the sound path 42. Figure 18 also shows Example [1]
because the acoustic material extends along the surface
walls of the sound path, but does not cover the surface
walls of the sound source space. Example [3] teaches an
embodiment where the pressure absorbing material and
acoustic material extend along both the sound path 42
and the sound source space 41. In this embodiment, both
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.                 19

of these materials would extend along the back wall of the
sound duct (the wall furthest from the output duct 45).
The parties do not dispute that acoustic material can be
sound absorbing material. Thus, Example [3] teaches a
back wall substantially following a curved contour of a
portion of a drive unit cone farthest opposite from the
output slot, made of sound absorbing material.
     We further conclude that claim 3 does not require “di-
rect proximity” between the speaker driver and the back
wall, and, thus, that the presence of a gap between Sa-
daie’s back wall and speaker cone is not inconsistent with
the teachings of the ’483 patent. Indeed, specific embodi-
ments in the ’483 patent include gaps between the back
wall of the duct and the speaker driver. ’483 patent, col.
9, ll. 20–32 (the edge of the speaker cone is not required to
“match[]the contours of the edge of the cylindrical hous-
ing” but may vary such that “the cone may be smaller
than the diameter of the cylindrical housing 405, or else
the speaker 407 may be positioned with an offset from
(above or below) the top edge of the cylindrical housing
405.”).
     We now consider whether a person of ordinary skill in
the art would have found a sufficient teaching or motiva-
tion to modify Tomonori’s straight back wall to the curved
shape described in Sadaie, even though there is no explic-
it teaching to that effect in Sadaie. There need not be an
explicit teaching to combine references in the prior art.
Depending on the nature of the technology and the
knowledge of those skilled in the art, a motivation to
make a particular modification may be a matter of com-
mon sense. KSR, 550 U.S. at 418, 420–21. While we do
not rely on common sense lightly, where, as here, the only
evidence of record supports the conclusion that the modi-
fication at issue is readily within the ken of those skilled
in the art, it is appropriate to do so.
20                  SLOT SPEAKER TECHNOLOGIES    v. APPLE INC.

     In addition to the evidence offered to support the find-
ing of a motivation to combine Sadaie with Tomonori to
practice claims 1 and 2, Apple proffered expert testimony
that it would not have been challenging to modify Tomon-
ori’s back wall to a curved one:
     Limitation 3(b) recites ‘said back wall substantial-
     ly following a curved contour of a portion of a
     drive unit cone farthest opposite from the output
     slot.’ . . [I]t would have been obvious to combine
     Tomonori with the teachings of Virva and Sadaie.
     It would have been obvious to one of ordinary skill
     in the art to use a back wall that substantially fol-
     lows a curved contour of a portion of a drive unit
     cone farthest opposite from the output slot. For
     example, Sadaie discloses that ‘[i]n a preferred
     embodiment, the above sound guiding part has a
     sound source space defined according to a periph-
     eral edge portion of the above speaker unit’. . .
     Straight and curved backwalls opposite a sound
     duct aperture are two among a limited number of
     options for shaping the back wall of a sound duct,
     and have both been commonly used in loudspeak-
     er design with predictable results. Given the
     ubiquity of curved and straight back walls, one of
     skill in the art would recognize the functions asso-
     ciated with each structure and the attendant ben-
     efits, and would select one for its known
     properties. Thus, it would have been obvious to
     shape the back wall of Tomonori to follow a con-
     toured edge of a drive unit, as taught by Sadaie
     and doing so would have been a matter of routine
     design choice.
J.A. 533, at ¶¶ 116-17 (internal citations omitted). Apple
supports its expert testimony by citing to a textbook
offered by Dr. Elliott, Slot Speaker’s expert, explaining
the different effects of loudspeaker cabinet shapes on
SLOT SPEAKER TECHNOLOGIES   v. APPLE INC.               21

sound diffraction. The textbook explains that the relative
effects of straight and curved walls in loudspeakers were
well known in the art. There is, moreover, no evidence to
suggest that a person of ordinary skill in the art would
not have been familiar with the costs and benefits of these
well-known design choices.
   For these reasons, we conclude that the Board erred
when it found that the combination of Tomonori and
Sadaie did not render claim 3 obvious.
                     IV. CONCLUSION
    For the foregoing reasons, we affirm in part and re-
verse in part the Board’s judgment.
   AFFIRMED IN PART, REVERSED IN PART
                          COSTS
   Costs to Apple.