(12) Ulllted States Patent
`Huang et al.
`
`([10) Patent N0.:
`(45) Date of Patent:
`
`US 6,173,059 B1
`Jan. 9, 2001
`
`US006173059B1
`
`4,658,425
`4,669,108
`4,696,043
`
`4.-703509
`
`4/1987 Julstrom ............................... .. 381/81
`5/1987 Dcinzcr
`379/61
`
`
`9/1987 Iwahara eta. ..
`381/92
`
`
`10/1987 sakamoto 6‘ a1-
`J11lSt1‘0I1'1 ............................. ..
`
`38}/92
`
`(List continued on next page.)
`
`11:”/110"Y EE"“”li’1er—_'éIa"id1dR~ZHud15PeIh
`Sslsmm xammer
`am . mte
`_
`(74) Attorney, Agent, or Fzrm—Kudirka & Jobse, LLP
`(57)
`ABSTRACT
`
`A telephone system includes two or more cardioid micro-
`Ph9If>S1V*[1?1E1‘°g€=the.TtaHd
`‘:11reC“°;d‘1>“‘WaF0t‘1Y fmmbe} Gen“?
`pom .
`ixmg circui ry an con ro circui ry com mes an
`analyzes signals from the microphones and selects the signal
`from one of the microphones or from one of one or more
`predetermined combinations of microphone signals in order
`to track a speaker as the speaker moves about a room or as
`Z3213‘iiieailiifiiciffififfl ?E§‘E2,$e0§??g?, Z‘§§{1l§,f§Z?o§§§
`(LEDS) are evenly spaced around the perimeter of a circle
`Congenmc with tbh.e H.1iCr°Ph°I1‘e EH3‘AMgdI]13g Ccirfiuiltgry
`Pm “C65 ten “Om mam“ 51%“ 5>
`+ >
`+ >
`+ >
`+ ’'
`C>A-13> 13-CaA:_C>A-_0~5(B+C} ‘B-0~5(A+C)> ahfl C_-0-5
`(B+A), with the listening beam‘ tormed by combinations,
`such as A—0.5(B+C), that involve the subtraction of signals,
`generally being more narrowly directed than beams formed
`by combinations, such as A+B, that involve only the addi-
`tion of signals. An omnidirectional combination A+B+C is
`employed when active speakers are widely scattered
`-
`-
`-
`Lhroughout the room. Wzighting factors are emgloyedl in. a
`nown manner l0.pI‘OV1 e iinity gain ontpiit.
`,ontro cir-
`cuitry selects the signal from the microphone or from one of
`the predetermined microphone combinations, based gener-
`ally on the energy level of the signal, and employs the
`selected signal as the output signal. The control circuitry
`also opera[eS [o
`dithering bewveen microphones and,
`by analyzing the beam selection pattern, may switch to a
`broader coverage pattern, rather than switching between two
`“mower beams that each Covers one of the Speakers‘
`
`19 Claims, 7 Drawing Sheets
`
`(54) TELECONFERENCING SYSTEM WITH
`VISUAL FEEDBACK
`
`(75)
`
`Inventors: Jixiong Huang, Brighton; Richard S.
`Grinne“, Brooklincg
`of
`
`(73) Assignee: Gentner Communications
`Corporation, Salt Lake City, UT (US)
`
`Under 35 U.S.C. l54(b), the term of this
`patent shall be extended for 0 days.
`
`(* ) Notice:
`.
`7
`(-1) Appl. No.. 09/066,163
`(22)
`Ffled:
`/Xpn 24,1998
`
`Int. Cl.7 ....................................................... H04R 1/40
`(51)
`(52) U.S. CI.
`............................................. .. 381/92; 379/202
`
`(58) Field of Search ............................. .. 381/92; 367/118,
`367/119, 121, 122, 124, 126; 379/202
`Referenees Cited
`U.S. PATENT DOCUMENTS
`8/ 973 Maston ..................................... 179/1
`9/ 975 Clearwaters et al.
`.
`340/6
`1/ 978 Dellar .............. ..
`179/1
`2/ 973 331,61 ,
`179/1
`5/ 978 Bauer ,,,,,,,,,,,,,, ,.
`,. 179/1
`12/ 978 Cliiistensen et al.
`179/1
`4/ 980 M6553 ~~~~~~ ~-
`357/126
`12/ 930 Bunting 6‘ a1~
`179/1
`3/ 981 speiser """ "
`343/100
`12/ 981 Massa .......... ..
`367/105
`12/ 981 Momose et al.
`179/1
`6/ 982 Wmy ............... N
`N 352/11
`8/ 983 Yamamoto et al.
`179/1
`10/ 933 Hagey ,,,,,,,,,,,,, N
`179/121
`11/ 983 Horie et al.
`.... .. 179/70
`3/ 984 Botros ................................ .. 179/121
`5/ 984 Lee el. al.
`........................... .. 381/110
`8/ 984 Gorike ----- ~-
`-- 381/29
`ilagagan
`"
`.
`n erson e a.
`..
`.
`1
`6/ 985 Miyaji et al.
`........................ .. 381/92
`12/ 985 Miyaji et al.
`........................ .. 381/92
`3/ 987 Hansen ................................. .. 381/92
`
`
`
`(59
`
`3,755,625
`3,906,431
`4,070,547
`4907215321
`4,095,353
`4,131,760
`4,198,705
`4,237,339
`‘L254-'417
`4,305,141
`4730815425
`4933415740
`4399327
`4,410,770
`4,414,433
`4,436,966
`4,449,238
`4»4°°>117
`,
`,
`4,521,908
`4,559,642
`4,653,102
`
`
`
`240°
`
`WAVES607_l0l3-0001
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`WAVES607_1013-0001
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`

`
`US 6,173,059 B1
`Page 2
`
`.............................. .. 381/92
`9/1993 Zagorski
`5,243,660
`10/1995 Bradley et al.
`...................... .. 381/92
`5,463,694
`1/1996 Zagorski
`..
`381/68.5
`5,483,599
`3/1996 Gun‘
`" 381/92
`5’5°0’903
`4/1996 B"““‘h"”°"J" ‘M1’
`" 381/92
`5506’908
`5,561,737 * 10/1996 Bowen ............................... .. 704/275
`
`............................ .. 381/92
`5,664,021
`9/1997 Chu 61.6.1.
`" 381/92
`57039957
`12/1997 M°A‘e°r.
`5,737,431
`4/1998 Brandstein et al.
`................. .. 381/92
`
`
`
`* cited by examiner
`
`US. PATENT DOCUMENTS
`.
`‘Z32; ‘*'- -------------------- 38315;‘;
`
`.......................
`6/1988 Kahn ....
`381/92
`3/1989 Minami .................................... 381/1
`8/1989 Fukushietal.
`. 381/106
`2/1990 Van Gemen etal.
`. 367/135
`10/1991 Kanamorietal.
`381/92
`
`6/1992 Baumhauer, Jr. et a.
`. 379/388
`5/1993 Ribic ................... ..
`381/68.1
`7/1993 Ono et al.
`............................ .. 381/92
`
`
`
`::»;fi=§‘3‘;}
`4,752,961
`4,815,132
`4’860':366
`4:903'.247
`5,058,170
`591215426
`5,214,709
`5,226,087
`
`WAVES607_1013-0002
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`WAVES607_1013-0002
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`

`
`U.S. Patent
`
`Jan. 9, 2001
`
`Sheet 1 of 7
`
`US 6,173,059 B1
`
`1200
`
`102
`
`240°
`
`120°
`
`
`
`240.,
`
`Figure 2
`
`VVA3H3S607_1013-0003
`
`PefifionerVVaVes£uuhoI¢d.607-JEX.1013
`
`WAVES607_1013-0003
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`

`
`U.S. Patent
`
`Jan. 9, 2001
`
`Sheet 2 of 7
`
`US 6,173,059 B1
`
`
`
`Figure 3
`
`240°
`
`120°
`
`
`
`240°
`
`Figure 4
`
`VVAAH3S607_1013-0004
`
`PefifionerVVaVes£uuhoI¢d.607-JEX.1013
`
`WAVES607_1013-0004
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`

`
`U.S. Patent
`
`Jan. 9, 2001
`
`Sheet 3 of 7
`
`US 6,173,059 B1
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`240°
`
`WAVES607_1013-0005
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`WAVES607_1013-0005
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`

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`U.S. Patent
`
`Jan. 9, 2001
`
`Sheet 4 of 7
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`US 6,173,059 B1
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`WAVES607_1013-0006
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`WAVES607_1013-0006
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`

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`U.S. Patent
`
`Jan. 9, 2001
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`Sheet 5 of 7
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`US 6,173,059 B1
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`Figure 8b
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`WAVES607_1013-0007
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`WAVES607_1013-0007
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`

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`U.S. Patent
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`Jan. 9, 2001
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`Sheet 6 of 7
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`US 6,173,059 B1
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`WAVES607_1013-0008
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`WAVES607_1013-0008
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`

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`U.S. Patent
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`Jan. 9, 2001
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`Sheet 7 of 7
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`US 6,173,059 B1
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`WAVES607_1013-0009
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`WAVES607_1013-0009
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
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`

`
`US 6,173,059 B1
`
`1
`TELECONFERENCING SYSTEM WITH
`VISUAL FEEDBACK
`
`FIELD OF THE INVENTION
`
`The invention relates generally to the reception, mixing,
`analysis, and selection of acoustic signals in a noisy
`environment, particularly in the context of speakerphone
`and telephone conferencing systems.
`BACKGROUND OF THE INVENTION
`
`Although tclcphonc technology has been with us for some
`time and, through a steady flow of innovations over the past
`century, has matured into a relatively effective, reliable
`means of communication,
`the technology is not flawless.
`Great strides have been made in signal processing and
`transmission of telephone signals and in digital networks
`and data transmission. Nevertheless,
`the basic telephone
`remains largely unchanged, with a user employing a handset
`that
`includes a microphone located near and directed
`towards the user’s mouth and an acoustic transducer posi-
`tioned near and directed towards the user’s ear. This arrange-
`ment can be rather awkward and inconvenient. In spite of the
`inconvenience associated with holding a handset,
`this
`arrangement has survived for many years: for good reason.
`The now familiar, and inconvenient,
`telephone handset
`provides a means of limiting the inclusion of unwanted
`acoustic signals that might otherwise be directed toward a
`receiver at the “other end” of the telephone line. With the
`telephone’s microphone held close to and directed toward a
`speaker’s mouth other acoustic signals in the speaker’s
`immediate vicinity are overpowered by the desired speech
`signal.
`However, there are many situations in which the use of a
`telephone handset is simply impractical, whether because
`the telephone user’s hands must be free for activities other
`than holding a handset or because several speakers have
`gathered for a telephone conference. “Hands free” telephone
`sets of various designs, including various speaker-phones
`and telephone conferencing systems, have been developed
`for just such applications. Unfortunately, speaker-phones
`and telephone conferencing systems in general
`tend to
`exhibit annoying artifacts of their acoustic environments. In
`addition to the desired acoustic signal from a speaker, echos,
`reverberations, and background noise are often combined in
`a telephone transmission signal.
`In audio telephony systems it is important to accurately
`reproduce the desired sound in the local environment, i.e.,
`the space in the immediate vicinity of a speaker, while
`minimizing background noise and reverberance. This selec-
`tive reproduction of sound from the local environment and
`exclusion of sound outside the local environment is the
`function at which a handset
`is particularly adept. The
`handset’s particular facility for this function is the primary
`reason that, in spite of their inconvenience, handsets never-
`theless remain in widespread use. For
`teleconferencing
`applications handsets are impractical, yet it is particularly
`advantageous to capture the desired acoustic signals with a
`minimum of background noise and reverberation in order to
`provide clear and understandable audio at the receiving end
`of telephone line.
`Anumber of technologies have been developed to acquire
`sound in the local environment. Some teleconferencing
`systems employ directional microphones, i.e., microphones
`having a fixed directional pickup pattern most responsive to
`sounds along the microphone’s direct axis, in an attempt to
`reproduce the selectivity of a telephone handset. If speakers
`
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`2
`are arranged within a room at predetermined locations which
`locations are advantageously chosen based upon the respon-
`sivity of microphones situated about the room, acceptable
`speech reproduction may be achieved. The directional selec-
`tivity of the directional microphones accents speech that is
`directed toward a microphone and suppresses other acoustic
`signals such as echo, reverberations, and other off-axis room
`sounds. Of course, if these undesirable acoustic signals are
`directed on-axis toward one of the microphones, they too
`will be selected for reproduction. In order to accommodate
`various speakers within a room, such systems typically gate
`signals from the corresponding microphones on or off,
`depending upon who happens to be actively speaking. It is
`generally assumed that the microphone receiving the loudest
`acoustic signal
`is the microphone corresponding to the
`active speaker. However, this assumption can lead to unde-
`sirable results, such as acoustic interference, which is dis-
`cussed in greater detail below.
`Moreover, it is unnatural and uncomfortable to force a
`speaker to constantly “speak into the microphone” in order
`to be heard. More recently, attempts have been made to
`accommodate speakers as the change positions in their seats,
`as they move about a conference room, and as various
`participants in a conference become active speakers. One
`approach to accommodating a multiplicity of active speakers
`within a conference room involves combining signals from
`two directional microphones to develop additional sensitiv-
`ity patterns, or “virtual microphones”, associated with the
`combined microphone signals. To track an active speaker as
`the speaker moves around the conference room, the signal
`from the directional microphone or virtual directional micro-
`phone having the greatest response is chosen as the system’s
`output signal. In this manner,
`the system acts,
`to some
`extent, as directional microphone that is rotated around a
`room to follow an active speaker.
`However, such systems only provide a limited number of
`directions of peak sensitivity and the beamwidth is typically
`identical for all combinations. Some systems employ micro-
`phone arrangements which produce only dipole reception
`patterns. Although useful in some contexts, dipole patterns
`tend to pick 11p noise and unwanted reverberations. For
`example, if two speakers are scatcd across a table from one
`another, a dipole reception pattern could be employed to
`receive speech from either speaker, without switching back
`and forth between the speakers. This provides a significant
`advantage, in that the switching of microphones can some-
`times be distracting, either because the speech signal
`changes too abruptly or because the background noise level
`shifts too dramatically. On the other hand, if a speaker has
`no counterpart directly across the table, a dipole pattern will,
`unfortunately, pick up the background noise across the table
`from the speaker, as well as that in the immediate vicinity of
`the speaker. Additionally, with their relatively narrow recep-
`tion patterns, or beams, dipole arrangements are not par-
`ticularly suite for wide area reception, as may be useful
`when two speakers, although seated on the same side of a
`conference table, are separated by some distance.
`Consequently, systems which employ dipole arrangements
`tend to switch between microphones with annoying fre-
`quency in such a situation. This is also true when speakers
`are widely scattered about the microphone array.
`One particularly annoying form of acoustic interference
`that crops up in the context of a telephone conference,
`particularly in those systems which select signals from
`among a plurality of microphones, is a result of the fact that
`the energy of an acoustic signal declines rapidly with
`distance. A relatively small acoustic signal originating close
`
`WAVES607_l0l3-00010
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`US 6,173,059 B1
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`3
`to a microphone may provide a much more energetic signal
`to a microphone than a large signal that originates far away
`from a microphone. For example, rustling papers or drum-
`ming fingers on a conference table could easily dominate the
`signal from an active speaker pacing back and forth at some
`distance from the conference table. As a result, the receiving
`party may hcar thc drumbcat of “Sing, Sing, Sing” poundcd
`out by fingertips on the conference table, rather than the
`considered opinion of a chief executive officer in the throes
`of a takeover battle. Oftentimes people engage in such
`otherwise innocuous activities without even knowing they
`are doing so. Without being told by an irritated conferee that
`they are disrupting the meeting, there is no way for them to
`know that they have done so, and they continue to “drown
`out” the desired speech. At the same time, the active speaker
`has no way of knowing that their speech has been suppressed
`by this noise unless a party on the receiving end of the
`conversation asks them to repeat a statement.
`SUMMARY OF THE INVENTION
`
`A telephone system in accordance with the principles of
`the present invention includes two or more cardioid micro-
`phones held together and directed outwardly from a central
`point. Mixing circuitry and control circuitry combines and
`analyzes signals from the microphones and selects the signal
`from one of the microphones or from one of one or more
`predetermined combinations of microphone signals in order
`to track a speaker as the speaker moves about a room or as
`various speakers situated about the room speak then fall
`silent.
`
`In an illustrative embodiment, an array of three cardioid
`directional microphones, A, B, and C, are held together
`directed outward from a central point and separated by 120
`degrees. Visual indicators,
`in the form of light emitting
`diodes (LEDs) are evenly spaced around the perimeter of a
`circle concentric with the microphone array. Mixing cir-
`cuitry produces ten combination signals, A+B, A+C, B+C,
`A+B+C, A—B, B—C, A—C, A—0.5(B+C), B—0.5(A+C), and
`C—0.5(B+A), with the “listening beam” formed by
`combinations, such as A—0.5(B+C), that involve the sub-
`traction of signals, generally being more narrowly directed
`than bcams formcd by combinations, such as A+B, that
`involve only the addition of signals. An omnidirectional
`combination A+B+C is employed when active speakers are
`widely scattered throughout the room. Weighting factors are
`employed in a known manner to provide unity gain output.
`That is, the combination signals are weighted so that they
`produce a response that is normalized to that of a single
`microphone, with the maximum output signal from a com-
`bination equal to the maximum output signal from a single
`microphone.
`Control circuitry selects the signal from the microphone
`from one of these predetermined microphone
`or
`combinations, based generally on the energy level of the
`signal, and employs the selected signal as the output signal.
`The control circuitry also operates to limit dithering between
`microphones and, by analyzing the beam selection pattern
`may switch to the omnidirectional reception pattern afforded
`by the A+B+C combination. Similarly, the control system
`analyzes the beam selection pattern to select a broader beam
`that encompasses two active speakers, rather than switching
`between two narrower beams that each covers one of the
`speakers. Through the addition and subtraction of the basic
`cardioid reception patterns,
`the control circuitry may be
`employed to form a wide variety of combination reception
`patterns. In the illustrative embodiment, the output micro-
`phone signal is chosen from one of a plurality of predeter-
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`is, although a plurality of
`mined patterns though. That
`combinations are employed, reception patterns typically are
`not eliminated, although patterns may be added,
`in the
`process of selecting and adjusting reception patterns.
`The control circuitry also operates the visual feedback
`indicator, i.e., a concentric ring of LEDs in the illustrative
`embodiment,
`to indicate the direction and width of the
`listening beam, thereby providing visual feedback to users
`of the system and allowing speakers to know when the
`microphone system is directed at them.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above and further advantages of the invention may be
`better understood by referring to the following description in
`conjunction with the accompanying drawings in which:
`FIG. 1 is a top plan view of the possible pickup response
`for a 3-microphone system.
`FIG. 2 is a top plan view of the pickup response provided
`when only one of the three microphone elements is used.
`FIG. 3 is a top plan view of the pickup response provided
`when two of the microphone elements responses are
`summed together equally.
`FIG. 4 is a top plan view of the possible pickup response
`provided when one microphone signal is subtracted from the
`signal of another.
`FIG. 5 is a top plan view of the possible pickup response
`provided when all
`three microphone signals are added
`equally.
`FIG. 6 is a top plan view of the possible pickup response
`when the signals of two microphones are added, scaled and
`subtracted from the signal of a third microphone.
`FIG. 7 is a top plan view of a LED microphone layout and
`LED pattern in accordance with the principles of the inven-
`tion.
`
`FIGS. 8a through 8d are top plan views, respectively, of
`the LED illumination patterns when one microphone signal
`is being used, the signals of two microphones are summed
`equally,
`the signals of all
`three microphones are added
`equally, and the signals of two microphones are added,
`scaled and subtracted from the signal of a third microphone.
`FIG. 9 is a functional block diagram showing the steps
`involved in beam selection and visual feedback for the
`
`microphone system.
`FIG. 10 is a conceptual block diagram of cascaded
`microphone arrays in accordance with the principles of the
`present invention.
`
`DETAILED DESCRIPTION
`
`A telephone system in accordance with the principles of
`the present invention includes two or more cardioid micro-
`phones held together and directed outwardly from a central
`point. Mixing circuitry and control circuitry combines and
`analyzes signals from the microphones and selects the signal
`from one of the microphones or from one of one or more
`predetermined combinations of microphones in order to
`track a speaker as the speaker moves about a room or as
`various speakers situated about the room talk then fall silent.
`The system may include, for example, an array of three
`cardioid directional microphones, A, B, and C, held together,
`directed outwardly from a central point, and separated by
`120 degrees. Directional indicators,
`in the form of light
`emitting diodes (LEDs) are evenly spaced around the perim-
`eter of a circle concentric with the microphone array each
`microphone generates an output signal designated as A, B,
`
`WAVES607_l0l3-00011
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`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`WAVES607_1013-00011
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`

`
`US 6,173,059 B1
`
`5
`respecitvely. Mixing circuitry produces combination
`C,
`signals, such as A+B, A+C, B+C, A+B+C, A—B, B—C,A—C,
`A—0.5(B+C), B—0.5(A+C), and C—.05(A+B), with the “lis-
`tening beam” formed by higher order combinations that
`include subtraction of signals, such as the A—0.5(B+C)
`combination, being more narrowly directed than that do not
`involve the subtraction of signals. Control circuitry selects
`the signal from the microphone or from one of the prede-
`termined microphone combinations, based generally on the
`energy level of the signal, and employs the selected signal as
`the output signal. Additionally, the control circuitry lights
`selected LEDs to indicate the direction and width of the
`listening beam. This automatic visual feedback mechanism
`thereby provides a speaker with a near-end indication of
`whether he is being heard and also provides others within the
`room an indication that they may be interrupting the con-
`versation.
`
`Referring to the illustrative embodiment of FIG. 1, a
`microphone system 100 assembled in accordance with the
`principles of the invention includes three cardioid
`microphones, A, B, and C, mounted 120 degrees apart, as
`close to each other and a central origin as possible. Each of
`the microphones has associated with it a cardioid response
`lobe, La, Lb, and Le, respectively. Microphones having
`cardioid response lobes are known. Various directional
`microphone response patterns are discussed in U.S. Pat. No.
`5,121,426, to Baumhauer, Jr. et al., which is hereby incor-
`porated by reference. The microphones, A, B, and C, are
`oriented outwardly from an origin 102 so that the null of
`each microphone’s response lobe is directed at the origin. By
`combining the microphones’ electrical response signals in
`various proportions, different system response lobes may be
`produced, as discussed in greater detail in the discussion
`related to FIG. 14.
`
`As seen is FIG. 1, each cardioid microphone has a
`response that varies with the off-axis angle fq according to
`the following equation:
`1/2+1/2 cos (I)
`
`(1)
`
`The response pattern described by this equation is the
`pear-shaped response shown by lobes La, Lb, and Lc for the
`microphones A, B, and C. Response lobe La is centered
`about 0 degrees, Lb about 120 degrees, and Le 240 degrees.
`As illustrated by equation (1), each microphone has a
`nomialized pickup value of unity along its main axis of
`orientation pointing outwardly from the origin 102, and a
`value of zero pointing in the opposite direction, i.e., towards
`the origin 102.
`The pear-shaped response pattern of a single microphone,
`microphone A, is more clearly illustrated the response chart
`of FIG. 2, where like components to those shown in FIG. 1
`are assigned like descriptors. Note that the response pattern
`of microphone A falls off dramatically outside the range of
`+—60 degrees. Consequently noise and reverberance outside
`that range, particularly to the rear of the microphone would
`have little effect on the signal produced by microphone A.
`Consequently,
`this arrangement could be used advanta-
`geously to reproduce sound from a speaker in that +—60
`degree range.
`By combining signals from various microphones a num-
`ber of response patterns may be obtained. The response lobe
`L(a+b) of FIG. 3 illustrates that a much broader response
`pattern may be obtained from a combination of cardioid
`microphones arranged as illustrated. With the inputs from
`microphones A and B each given equal weight then added,
`the response pattern L(a+b) is described by the following
`equation:
`
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`(%+% cos q2)+(%+% cos(q2—120))=1+%(cos q)+cos((])—120))
`
`(2)
`
`A multiplicative gain would be applied to this signal to
`normalize to unity gain. That is, the response of each of the
`microphones combined in a simple addition would be mul-
`tiplied by 2/3. This response pattern provides a wider accep-
`tance angle than that of a single cardioid microphone, yet,
`unlike a combination of dipole, or polar, microphones, still
`significantly reduces the contribution of noise and rever-
`beration from the “rear” of the response pattern, i.e., from
`the direction of the axis of microphone C. This response
`pattern would be particularly useful in accepting sounds
`within the range of -60 and 180. A broader acceptance angle
`such as this is particularly advantageous for a situation
`where two speakers are located somewhere between the axes
`of microphones A and B. A wider acceptance angle such as
`this permits a system to select a signal corresponding to this
`broader acceptance angle, rather than dithering between
`signals from microphonesA and B as a system might, should
`dipole response patterns be all that were available to it. Such
`dithering is known in the art to be a distraction and an
`annoyance to a listener at
`the far end of a telephone
`conference. Being able to avoid dithering in this fashion
`provides a significant performance advantage to the inven-
`tive system.
`That is not to say that a dipole response pattern is never
`desirable. As illustrated in the response pattern of FIG. 4, a
`dipole response pattern may be obtained, for example, by
`subtracting the response of microphone B from that of
`microphone A. In FIG. 4 a dipole response lobe L(a—b) is
`produced by subtracting the response of microphone B from
`that of microphone A according to the following equation:
`
`(1/2+1/2 cos (|):)—(1/2+1/2 cos(q)—12(l))=1/2 cos (])—(1/2 cos((])—120))=1/2(cos
`¢—cos(¢—120))=0.866(cos((]>+-30)
`(3)
`
`A multiplicative gain would be applied to this signal to
`normalize to unity gain. By subtracting the signal of B from
`that of A, a narrower double sided pickup pattern is pro-
`duced.
`In this example,
`the pattern effectively picks up
`sound between -75 and 15 degrees, and 105 and 195
`degrees. This is especially well-suited for scenarios where
`audio sources are located to either side of the microphone,
`especially along broken line 104, and noise must be reduced
`from other directions.
`
`Additional response patterns may be produced by using
`all three microphones. For example, FIG. 5 illustrates a
`response pattern that results from the addition of equally
`weighted signals from microphones A, B and C, which
`produces an omni-directional response pattern according to
`the following equation:
`
`(1/2+1/2 cos ¢)+(1/2+1/2 cos(q)—120))+(1/é+1/2 cos(q)+12O))=1.5+1/2(cos
`q)+cos(q)—120)+cos ((I)+120))=1.5
`
`(4)
`
`A multiplicative gain would be applied to this signal to
`normalize to unity gain. This angle-independent response
`allows for sounds from sources anywhere about the micro-
`phone array to be picked up. However, no noise or rever-
`berance reduction is achieved.
`
`As illustrated by the response pattern of FIG. 6, signals
`from all three microphones may be combined in other ways
`to produce, for example, the narrow dipole response pattern
`L(a—0.5(b+c)). The resulting narrow dipole pattern is
`directed toward 0 and 180 as described by the following
`equation:
`
`(1/2+1/2 cos c|))—0.5((1/é+1/2 cos(c|)—120))+(1/2+1/2 cos(<|)+120)))=
`
`(1/2+1/2 cos q))—0.25(1+cos q)—120)+cos(q)+120))=
`
`WAVES607_l0l3-00012
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`WAVES607_1013-00012
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1013
`
`

`
`US 6,173,059 B1
`
`7
`1/; cos ¢—O.25(cos(¢—120)+cos(¢+120))=
`
`0.75 cos (pf
`
`A multiplicative gain would be applied to this signal to
`normalize to unity gain. With this combination, the pattern
`effectively picks up sound between -45 and 45 degrees, and
`between 135 and 225 degrees. This response pattern is
`especially well-suited for scenarios where audio sources are
`located to either side of the microphone, and noise must be
`reduced from other directions.
`
`In the illustrative embodiment, responses from predeter-
`mined microphones and microphone combinations, such as
`that provided by microphones A, B, and C, and by micro-
`phone combinations A+C, A+B, B+C, A+B+C, A—B, B—C,
`A—C, A—0.5(B+C), B—0.5(A+C), and C—0.5(A+B) are ana-
`lyzed and one of the predetermined combinations is
`employed as the output signal, as described in greater detail
`in the discussion related to FIG. 14.
`In the illustrative embodiment, the microphone system
`includes six LEDs arranged in a concentric circle around the
`perimeter of the microphone array 100, with LEDs 106, 108,
`110, 112, 114, and 116 situated at 0, 60, 120, 180, 240, and
`300 degrees, respectively. As the LEDs are used for visual
`feedback, more or fewer LEDs could be employed, and any
`of a number of other visual indicators, such as an LCD
`display that displays a pivoting virtual microphone, could be
`substituted for the LEDs. The number and direction of LEDs
`lit indicates the width and direction of the reception pattern
`that has been selected to produce the telephone output
`signal. FIGS. 8a through 8b illustrate the LED lighting
`patterns corresponding to various reception pattern selec-
`tions. In FIG. 8a, for example, LED 106 is lit to indicate that
`reception pattern La has been selected. Similarly, in FIG. 8b,
`LEDs 106, 108, and 110 are lit to indicate that the lobe, or
`reception pattern, L(a+b). In FIG. 8c all the LEDs are lit to
`indicate that the omnidirectional pattern L(a+b+c) has been
`selected. And,
`in FIG. 8d, LEDs 106 and 112 are lit to
`indicate that the L(a—0.5(b+c)) pattern has been selected.
`The LED lighting pattern will typically be updated at the
`same time the response pattern selection decision is made.
`Signal mixing, selection of reception patterns, control of
`the audio output signal and control of the visual indicators
`may be accomplished by an apparatus 900 which, in the
`illustrative embodiment, is implemented by a digital signal
`processor according to the functional block diagram of FIG.
`9. Each microphone A, B, C, produces an electrical signal
`MA, MB, MC, respectively, in response to an acoustic input
`signal. The analog response signals, MA, MB, and MC for
`each microphone are sampled at 8,000 samples per second.
`Digitized signals from each of the three microphones A,B,
`and C are combined with one another to produce a total of
`thirteen microphone signals MA, MB, MC, M(A+B), etc.,
`which provide maximum signal response for each of six
`radial directions spaced 60° apart and other combinations as
`discussed above. Response signals M(A+B), M(A+C), M(B+C),
`etc., are formed by weighting, adding and subtracting the
`individual sampled response signals, thereby producing a
`total of thirteen response signals as previously described.
`For example, wMA+(1—w)M3=M(A+B), where W is a weigh-
`ing factor less than one, chosen to produce a response
`corresponding to a microphone situated between micro-
`phones A and B.
`Because each of the thirteen signals is operated upon in
`the following manner before being operated upon in the
`beam selection functional block 910, only the operation
`upon signal MA, will be described in detail, the same process
`applies to all thirteen signals. The digital signals are deci-
`
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`mated by four in the decinrator 902 to reduce signal pro-
`cessing requirements. Signal energies P,.(_k) are continuously
`computed in functional block 904 for 16 ms signal blocks
`(32 samples) related to each of the thirteen response signals,
`by summing the absolute values of the thirty-two signal
`samples within each 16 ms block; i.e., totaling the thirty-two
`absolute values of signa