(12) United States Patent
`Yoshino et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,813,577 B2
`Nov. 2, 2004
`
`US006813577B2
`
`(54)
`
`(75)
`
`Inventors: Hajilne Yoshino, Tokorozawa (JP);
`Kazuya Tsukada’ Tokorozavva (JP)
`
`(73) Assignee: Pioneer Corporation, Tokyo-to (JP)
`_
`_
`I
`p
`p
`( * ) Notice:
`SubJeet to any disclaimer, the term of H118
`patent is extended or adjusted under 35
`U.S.C. 154(1)) by 79 days.
`,
`(21) Appl No‘ 10/131364
`(22)
`Filed;
`Apt 25, 2002
`
`(65)
`
`Prior Publication Data
`
`6,570,991 B1
`20020010587 A1
`
`5/Z003 Scheirer el al.
`1/2002 l"€It1’llShil'1
`
`381/110
`.. 7U4/275
`
`~~ 381/124
`10/2002 Ric? et 111-
`2002/V015‘/_l787 A1
`....... .. 704/225
`3/Z003 Tllzjak
`2003/0055635 A1
`FOREIGN PATENT DOCUMENTS
`
`ET‘
`EP
`JP
`JP
`JP
`JP
`JP
`JP
`VVO
`W0
`
`0 575 619
`1 081 694
`10199126
`10208375
`10326454
`2000048474
`2000050565
`2001043004
`97/01168
`00/931090
`
`12/1993
`3/2001
`7/1998
`8/1998
`12/1998
`2/2000
`2/2000
`2/2001
`1/1997
`4/2000
`
`US 2002/0161543 A1 Oct. 31, 2002
`
`* cited by examiner
`
`Foreign Application Priority Data
`(30)
`Apr. 27, 2001
`(JP)
`..................................... .. 2001433573
`-
`(51)
`Int. Cl.’ .............................................. .. G06F 13/14
`(52) U.s. Cl.
`...................... ._ 702/111, 702/112, 702/116;
`702/124
`. . . .. 702/112, 116,
`(58) Field of Search . . . . .
`702/124, 18-, 183, 39, 48, 103, 111, 191,
`193, 84/477 R, 181/119, 704/251, 56,57,
`275, 600/587, 381/58
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,792,072 A *
`8/1998 Keefe ....................... .. 600/559
`5,920,840 A *
`7/1999 Satyamurti et al.
`....... .. 704/267
`6,219,645 B1 *
`4/2001 Byers ....... ..
`704/275
`6,560,350 B2 *
`5/2003 Rhoads
`.... .. 382/100
`
`& Th
`
`Ompson
`
`Priflmry ExLm”.”er_Ma[C S. Hoff
`Assistant EX[lI11i)1€r—FCllX Suarez
`74 A
`', A
`,
`' F 7
`/Y
`(
`)
`rmm"
`gem‘ 0' W"
`Oung
`(57)
`ABSTRACT
`By the speaker detecting device, the test signal is supplied
`to the output terminal to which the speaker is to be con-
`nected. If a speaker is connected to the output tenninal, the
`test sound is output Via the speaker.
`If no speaker is
`connected to the output terminal, no test sound is output. The
`test sound detecting unit detects the test sound in the
`acoustic space and compares the signal level of the test
`sound with the predetermined threshold level. thereby to
`judge Whether or not a speaker is connected to the output
`terminal.
`
`.55; 1-Hz
`,
`SPF TO
`-SE ' VARIABLE NIP
`TH
`1:1-1 STATE
`
`DETECT ENVIROHENTAL
`nurse LE‘/E.
`
`sa
`
`ENVIRONMENTAL
`ms: <m1 '3
`
`AIIALYSE sescmm or
`HMROMIIENTALNOISE
`'
`'SELEC1 FREQUENCY BAND
`-DETERMINE
`2
`»séT BF
`-SET VANABLEAMP
`
`»AIJTPIH 'n:s1' sum
`-cougar souun av Mic
`'DETEDI‘ TEST SJGNAL LEVEL
`
`seamensosreux
`JUDGMENT
`
`as nzsuu: or
`A1’ CHANNEL
`
`11 Claims, 9 Drawing Sheets
`
`MS_Biscotti_0061923
`
`

`
`U.S. Patent
`
`Nov. 2, 2004
`
`9£101tee_hS
`
`US 6,813,577 B2
`
`Jmam
`
`Jam
`
`mama
`
`mum
`
`a2<
`
`omm
`
`om
`
`a2<
`
`g2<
`
`Jmmm
`
`Jam
`
`mxam
`
`mam
`
`m2<
`
`¢2<
`
`mam
`
`m2<
`
`.53'I
`
`¢2<
`
`mmmmm
`
`mmmm
`
`Jmmmm
`
`Jmmm
`
`4<zo_mHam»
`
`mo»<¢mzmo
`
`4<zo_m
`
`oz_mmmooam
`
`H_:om_o
`
`ozaom
`
`momnom
`
`MS Biscotti 0061924
`
`

`
`U.S. Patent
`
`Nov. 2,2004
`
`Sheet 2 of9
`
`US 6,813,577 B2
`
`FIG.2
`
`SIGNAL
`PROCESSING
`UNIT
`
`COEFFICIENT
`OPERATION
`UNIT
`
`MS_Biscotti_0061925
`
`

`
`U.S. Patent
`
`Nov. 2, 2004
`
`9£103teChS
`
`US 6,813,577 B2
`
`~u»<
`
`mo»<
`
`~op<
`
`m2<m4m<_z<>
`
`mu+<
`
`
`
`m2<m4m<_m<>
`
`vo»<
`
`¢E<m4m<_m<>
`
`m:<m4m<_m<>
`
`mo+<
`
`~o»<
`
`mo»<
`
`m2<m4m<_z<>
`
`mz<m4m<_m<>
`
`m2<m4m<_m<>
`
`m2<m4m<_x<>
`
`
`
`4<zo_mham»
`
`mo»<mmzmo
`
`MS_Biscotti 0061926
`
`

`
`U.S. Patent
`
`Nov. 2, 2004
`
`Sheet 4 of 9
`
`US 6,813,577 B2
`
`MEMORY
`
`TO SIGNAL PROCESSING
`UN|T20
`
`SPECTRUM
`ANALYZlNG
`
`DETECTING
`UN!T
`
`MS_Biscotti_0061927
`
`

`
`U.S. Patent
`
`Nov. 2,2004
`
`Sheet 5 of9
`
`US 6,813,577 B2
`
`FlG.5
`
`SPEAKER
`DETECTION
`
`.351 TH2
`.3ET 3pF To
`THROUGH STATE
`-SET VARIABLE AMP
`
`DETECT ENVIRO MENTAL
`NOISE LEVEL
`
`ENVIRONMENTAL
`NOISE <TH1 ‘?
`
`ANALYSE SPECTRUM OF
`ENVIRONMENTAL NOISE
`
`‘SELECT FREQUENCY BAND
`‘DETERMINE TH2
`-SET BPF
`-SET VARIABLE AMP
`
`-OUTPUT TEST SIGNAL
`'COLLECT SOUND BY MIC
`‘DETECT TEST SIGNAL LEVEL
`
`SPEAKER EXISTENCE
`JUDGMENT
`
`STORE RESULD OF
`THAT CHANNEL
`
`MS_Biscotti_0061928
`
`

`
`U.S. Patent
`
`V.0N
`
`40022:
`
`Sheet 6 of 9
`
`US 6,813,577 B2
`
`FREQUENCY
`
`MS Biscotti 0061929
`
`

`
`U.S. Patent
`
`Nov. 2, 2004
`
`Sheet 7 of 9
`
`US 6,813,577 B2
`
`F|G.7
`
`SPEAKER EXISTENCE
`
`JYDGMENT
`
`SPEAKER
`CONNECTED
`
`N0 SPEAKER
`CONNECTED
`
`RETURN
`
`MS_Biscotti_0061930
`
`

`
`U.S. Patent
`
`Nov. 2,2004
`
`Sheet 8 of9
`
`US 6,813,577 B2
`
`MS_Biscotti_0061931
`
`SPEAKER
`SFL
`)
`
`SPEAKER
`6C
`
`SPEAKER
`SFR
`
`[:]—vewF
`SUB-WVOOFER
`
`RV(8)
`
`LI STENING PCS ITION
`
`?0
`
`SPEAKER
`
`ERR
`
`SSBL
`SURROUND
`S PEAKER
`
`SURROUND
`SPEAKER
`
`

`
`U.S. Patent
`
`Nov. 2, 2004
`
`Sheet 9 of 9
`
`US 6,813,577 B2
`
`DATA SIGNAL
`
`SERVER,etc
`
`STORAGE MEDIUM
`
`MS_Biscotti_0061932
`
`

`
`US 6,813,577 B2
`
`1
`SPEAKER DETECTING DEVICE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to an audio system using a plurality
`of speakers to create a high-quality sound field space, and
`more particularly to a technique for automatically detecting
`state of speaker connection to the audio system.
`2. Description of Related Art
`For an audio system to provide a high—quality sound field
`space, it is required to automatically create a sound field
`space with presence by using a plurality of speakers.
`Therefore,
`it is necessary to set the configuration of the
`speaker system used in the audio system, in advance, in the
`audio system.
`Conventionally, a user connects a plurality of speakers to
`the audio system and then manually inputs the speaker
`system configuration to the audio system.
`As a method of automatically detecting the speaker sys-
`tem configuration,
`it
`is conceivable to detect
`impedance
`variation of the audio system viewed from the side of the
`amplifier in the audio system so that the audio system can V
`automatically detect the presence or absence of the speaker.
`Namely, since the impedance of the audio system viewed
`from the amplifier side changes according to the presence or
`absence of the speaker connected, the presence or absence of
`the speaker can be detected by detecting the impedance
`variation in the case a predetermined test signal is output.
`However, the above -described method requires an exclusive
`hardware to detect the presence or absence of the speaker.
`SUMMARY OF THE INVENTION
`
`It is an object of the present invention to provide a speaker
`detecting device capable of automatically detecting speakers
`connected to the audio system, Without being a ected by
`environmental noise.
`
`According to one aspect of the present invention, there is
`provided a speaker detecting device including: an output
`terminal for outputting a signal to drive a speaker; a test
`signal supplying unit for supplying the test signal to the
`output terminal; a test sound detecting unit, installed in an
`acoustic space in Which the speaker is installed, for detecting
`a test sound corresponding to the test signal; and a speaker
`existence judging unit for judging whether or not a speaker
`is connected to the output terminal by comparing a signal
`level of the test sound, detected by the test sound detecting
`unit when the test signal supplying unit supplies the test
`signal to the output terminal, with a predetermined threshold
`level.
`According to the speaker detecting device thus
`configured, the test signal is supplied to the output terminal
`to which the speaker is to be connected. If a speaker is ,,
`connected to the output terminal, the test sound is output via
`the speaker.
`If no speaker is connected to the output
`terminal, no test sound is output. The test sound detecting
`unit detects the test sound in the acoustic space and com-
`pares the signal level of the test sound with the predeter-
`mined threshold level, thereby to judge Whether or not a
`speaker is connected to the output terminal.
`The speaker detecting device may further include: an
`environmental noise detecting unit for detecting environ-
`mental noise in the acoustic space; and an optimum fre-
`quency band determining unit for determining an optimum
`frequency band of the test signal by analyzing a level of the
`
`2
`environmental noise in terms of spectrum. In that case, tie
`speaker existence judging unit may compare the level of tie
`signal in the optimum frequency band, out of the signals
`detected by the test sound detecting unit. with the predeter-
`mined threshold level. By this, since the optimum frequency
`band is determined based on the spectrum analysis of [16
`environmental noise, the speaker existence can bejudged by
`using the frequency band with small environmental noise.
`The optimum frequency band determining unit may deter-
`mine the frequency band having a highest acoustic S/N ra io
`as the optimum frequency band. Thus, the accuracy in t1e
`speaker existence detection may be improved.
`The optimum frequency band determining unit may
`include: a 11nit for storing a predetermined signal curve da a;
`a unit for detecting the level of the environmental noise
`detected by the environmental noise detecting unit for each
`of multiple frequency bands to produce a noise curve da a;
`and a unit for determining the frequency band having tie
`highest acoustic S/N ratio as the optimum frequency band by
`comparing the curve data with the noise curve data. With
`this configuration, since the optimum frequency band is
`determined based on the signal curve data determined in
`consideration of auditory sensitivity of human being and the
`environmental noise data, it is possible to prevent a person
`in the acoustic space from feeling uncomfortable by the test
`sound.
`
`The speaker detecting device may further include a
`threshold level setting unit for setting a level between the
`signal curve data and the noise curve data in the optimum
`frequency band to the predetermined threshold level. Thus,
`an appropriate threshold value may be set based on the
`actual S/N ratio in the optimum frequency band.
`The speaker existence _judging unit may judge the exist-
`ence of the speaker based on the signal level in the optimum
`frequency band when the level of the environmental noise is
`larger than a predetermined reference level, and may judge
`the existence of the speaker based on the signal level of all
`frequency bands when the level of the environmental noise
`is smaller than the predetermined reference level. By this,
`when the environmental noise is large, the test signal of the
`optimum frequency band is used to accurately judge the
`speaker existence. When the environmental noise is small,
`not only the optimum frequency band, the test signal of all
`frequency bands is used to quickly detect
`the speaker
`existence.
`
`The test signal supplying unit may supply only a com-
`301‘l€11t of the test signal in the optimum frequency ba11d to
`he output terminal. By this, it is possible to avoid that a
`aerson in the acoustic space feels uncomfortable due to the
`unnecessarily large sound by reproducing the component
`hat does not contribute to the speaker existence judgment.
`The test sound detecting unit and the environmental noise
`detecting unit may be integrally configured as a single
`acoustic detecting unit. Thus, the configuration needed for
`he speaker detection may be simplified.
`According to another aspect of the present invention,
`here is provided a program storage device readable by a
`computer having an output terminal for outputting a signal
`o drive a speaker and tangibly embodying a program of
`instructions executable by the computer to control the com-
`auter to function as a speaker detecting device including: a
`est signal supplying unit for supplying the test signal to the
`output terminal; a test sound detecting u11it, installed in an
`acoustic space in which the speaker is installed, for detecting
`a test sound corresponding to the test signal; and a speaker
`existence judging unit for judging whether or not a speaker
`
`MS_Biscotti_0061933
`
`

`
`US 6,813,577 B2
`
`3
`is connected to the output terminal by comparing a signal
`level of the test sound, detected by the test sound detecting
`unit when the test signal supplying unit supplies the test
`signal to the output terminal, with a predetermined threshold
`level.
`
`According to still another aspect of the present invention,
`there is provided a computer data signal embodied in a
`carrier wave and representing a series of instructions which
`causes a computer, having an output terminal for outputting
`a signal to drive a speaker, to function as a speaker detecting
`device including: a test signal supplying unit for supplying
`the test signal to the output terminal; a test sound detecting
`unit, installed in an acoustic space in which the speaker is
`installed, for detecting a test sound corresponding to the test
`signal; and a speaker existence judging unit for judging
`whether or not a speaker is connected to the output terminal
`by comparing a signal level of the test sound, detected by the
`test sound detecting unit when the test signal supplying unit
`supplies the test signal
`to the output
`terminal, with a
`predetermined threshold level.
`By reading the program into computer and executing it,
`the computer may function as the above-described speaker
`detecting device.
`The nature, utility, and further features of this invention ,
`will be more clearly apparent from the following detailed
`description with respect
`to preferred embodiment of the
`invention when read in conjunction with the accompanying
`drawings briefly described below.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram showing a configuration of an
`audio system employing a speaker detecting device accord-
`ing to an embodiment of the present invention;
`FIG. 2 is a block diagram showing an internal configu-
`ration of a signal processing circuit shown in FIG. 1;
`FIG. 3 is a block diagram showing a configuration of a
`signal processing unit shown in FIG. 2;
`FIG. 4 is a block diagram showing a configuration of a
`coefiicient operation unit shown in FIG. 2;
`FIG. 5 is a flowchart showing a speaker detection process;
`FIG. 6 is a graph showing examples of a signal curve and
`a noise curve;
`FIG. 7 is a flowchart showing a speaker existence judg-
`ment step shown in FIG. 5;
`FIG. 8 is a diagram showing an example of speaker
`arrangemetit in a certain sound field environment; and
`FIG. 9 shows a concept of application of the present
`invention to computer program.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`[1] System Configuration
`A preferred embodiment of a speaker detecting device ..
`according to the present invention will now be described
`below with reference to the attached drawings. FIG. 1 is a
`block diagram showing an audio system employing the
`speaker detecting device according the embodiment of the
`invention.
`In FIG. 1, the audio system 100 includes a sound source
`1 such as a CD (Compact Disc) player or a DVD (Digital
`Video Disc or Digital Versatile Disc) player, a signal pro-
`cessing circuit 2 to which the sound source 1 supplies digital
`audio signals SFL, SFR, SC, SRL, SRR, SWF, SSBL and
`SSBR via the iiiulti-chaiinel signal transmission path, and a
`test signal generator 3.
`
`4
`While the audio system 100 includes the multi—channel
`signal
`transmission paths,
`the respective channels are
`referred to as “lst-channel” to “8th-channel” in the order
`from the top to the bottom in FIG. 1, according to need. In
`addition, the subscripts of the reference number are omitted
`to refer to all of the multiple channels when the signals or
`components are expressed. On the other hand, the subscript
`is put to the reference number when a particular channel or
`component
`is referred to. For example,
`the description
`“digital audio signals S” means the digital audio signals SFL
`to SSBR, and the description “digital audio signal SFL”
`means the digital audio signal of only the FL—channel.
`Further,
`the audio system 100 includes D/A converters
`4FL to 4SBR for converting the digital output signals DFL
`to DSBR of the respective channels processed by the signal
`processing by the signal processing circuit 2 into analog
`signals, and amplifiers SFI.
`to SSBR for amplifying the
`respective analog audio signals output by the D/A converters
`4FL to 4SBR. In this system, the analog audio signals SPFI_
`to SPSBR after the amplification by the amplifiers SFL to
`SSBR are supplied to the multi—channel speakers 6FL to
`6SBR positioned in a listening room 7, shown in FIG. 8 as
`an example, to output sounds.
`The audio system 100 also includes a microphone 8 for
`collecting reproduced sounds at the listening position RV in
`the listening room 7, an amplifier 9 for amplifying a col-
`lected sound signal SM output from the microphone 8, and
`an A/D converter 10 for converting the output of the
`amplifier 9 into a digital collected sound data DM to supply
`it to the signal processing circuit 2.
`As shown in FIG. 8,
`the audio system 100 activates
`full-band type speakers 6FL, GFR, 6C, 6RL, 6RR having
`frequency characteristics capable of reproducing sound for
`substantially all audible frequency bands, a speaker 6VVF
`having a frequency characteristic capable of reproducing
`only low-frequency sounds and surround speakers 6SFlI. and
`6SBR positioned behind the listener, thereby creating sound
`field with presence around the listener at
`the listening
`position RV.
`With respect to the position of the speakers, as shown in
`FIG. 8, for example, the listener places the two-channel, left
`and right speakers (a front-left speaker and a front-right
`speaker) 6FL, 6FR and a center speaker 6C, in front of the
`listening position RV, according to the listener’s taste. Also
`the listener places the two-channel, left and right speakers (a
`re ar-left speaker and a rear-right speaker) 6RI., SRR as well
`as two-channel,
`left and right surround speakers 6SBL,
`GSBR behind the listening position RV, and further places
`the sub-woofer 6VVF exclusively used for the reproduction
`of low—frequency sound at any position.
`The signal processing circuit 2 may have a digital signal
`processor (DSP), and roughly includes a signal processing
`unit 20 and a coe icient operating unit 30 as shown in FIG.
`2.
`
`The audio system shown in FIG. I operates in two modes.
`One is a sound source reproduction mode in which the audio
`signal output by the sound source shown in FIG. 1 is
`reproduced from a plurality of speakers. The other mode is
`a speaker detection mode, which is executed prior to the
`sound source reproduction mode. In the speaker detection
`mode, the existence, ie, the presence or the absence of the
`speaker connected to the audio system 100 is automatically
`judged.
`In the sound source reproduction mode, the signal pro-
`cessing unit 20 receives the multi—channel digital audio
`signals from the sound source 1 reproducing sound from
`various sound sources such as CD, DVD or else, perfonris
`
`MS_Biscotti_0061934
`
`

`
`;-
`D
`
`US 6,813,577 B2
`
`necessary processing and outputs the digital output signals
`DFL to DSBR. In the speaker detection mode, the signal
`processing unit 20 outputs the test signal from the test signal
`generator 3 via the transmission paths of the respective
`channels. Further, the signal processing unit 20 collects the
`test signal thus output by the microphone 8, and returns the
`test signal to the signal processing circuit 2. The signal
`processing circuit 2 processes the returned test signal to
`detect the existence of the speaker.
`FIG. 3 shows the configuration of the signal processing
`unit 20. In FIG. 3, the 1st to 8th channels FL to FBR include
`band-pass filters BPF1 to BPF8, and variable amplifiers
`ATG1 to ATG8 at the following stage of the band-pass filters
`BPF1 to BPF8. The signal processing unit 20 also includes
`the test signal generator 3 for outputting a test signal for the
`speaker detection, switches SW11 to SW81 and SW12 to
`SW82 provided for the respective channels, and a switch
`SWN for selectively supplying the output signal DN from
`the test signal generator 3 to the band-pass filters of the
`respective channels.
`the switches
`In the sound source reproduction mode,
`SWN and SW11 to SW81 are turned OFF and the switches
`SW12 to SW82 are turned ON. By this, the signals SFL to
`SSB are supplied to the corresponding band-pass filters
`BPF1 to BPF8, respectively. Each of the band-pass filters is '
`set to the through-state, and supplies the input signal to the
`variable amplifiers ATG1 to ATG8 for all frequency bands.
`The variable amplifiers ATG1 to ATG8 amplify the signals
`of the respective channels by appropriate amplitudes for the
`respective channels in accordance with the control signal SG
`supplied by the coeflicient operation unit 30, and supplies
`the amplified signals to the D/A converters 4FL to 4SBR in
`FIG. 1 as the digital signals DFL to DSBR. It is noted that,
`while the setting of the respective variable amplifiers ATG1
`to ATG8 in the sound source reproduction mode is deter-
`mined by an appropriate sound field correction process, the
`process is not directly related to the present invention, and
`hence the detailed description thereof will be omitted. Thus,
`in the sound source reproduction mode, the audio signals
`from the sound source 1 are reproduced by the channel unit.
`On the other hand, in the speaker detection mode,
`the
`switches SWN and SW11 to SW81 are turned ON and the
`switches SW12 to SW82 are turned OFF. Therefore, the test
`signal DN is supplied from the test signal generator 3 to the
`respective band-pass filters BPF1 to BPF8, and the speaker
`detection process described later in detail is executed.
`FIG. 4 shows a configuration of the coe icient operation
`unit 30. As shown, the coeflieient operation unit 30 includes
`a spectrum analyzing unit 11, a level detecting unit 12, a
`system controller MPU, a band-pass filter 17, and a memory
`15. it is noted that the spectrum analyzing unit 11, the level
`detecting unit 12 and the band-pass filter 17 constitute DSP
`(Digital Sound Processor).
`In the speaker detection mode, the coefficient operation
`unit 30 generates the control signal SF1 for controlling the ..
`pass bands of the band-pass filters BPF1 to BPF8 in the
`signal processing unit 20, and also generates the control
`signal SG for controlling the amplitudes of the variable
`amplifiers ATG1 to ATG8 in the signal processing unit 20.
`The coe ieient operation unit 30 supplies the control signals
`SF1 an SG to the signal processing unit 20.
`Specifically, the spectrum analyzing unit 11 first receives
`the collected sound data DM obtained by collecting ambient
`sound by the microphone 8 iii the state the speakers 6FL to
`6SBR output no signal, and analyzes the spectrum of the
`collected sound data DM. Namely, the spectrum analyzing
`unit 11 divides the collected sound data DM into 9 frequency
`
`6
`bands (eg, 9 frequency bands from low-frequency band to
`high-frequency band), and detects the levels of the signals in
`the respective frequency bands to analyze the spectrum of
`the collected sound data DM of the environmental noise.
`Then, the spectrum analyzing unit 11 supplies the level data
`21 indicating the levels of the respective frequency bands to
`the system controller MPU.
`The band-pass filter 17 extracts the component of a
`certain frequency band and supplies it to the level detecting
`unit 12. The level detecting unit 12 detects the signal level
`ofthe frequency band that the band-pass filter 17 passed, and
`supplies the detection level data 22 to the system controller
`MPU.
`The memory 15 stores threshold levels TH1 and TH2
`described later, a signal curve determined in consideration of
`auditory characteristics of human being, and the speaker
`existence judgment result for the respective channels
`obtained by the speaker existence judgment process.
`The system controller MPU receives the level data 21 of
`the respective frequency bands from the spectrum analyzing
`unit 11. The system controller MPU also receives the level
`data 22 indicating the level of the frequency band extracted
`by the band-pass filter 17, compares it with the threshold
`levels TII1 to TII2 stored in the memory 15 to generate the
`control signals SF1 and SG, and supplies the control signals
`SF1 and SG to the signal processing unit 20.
`[2] Process in Speaker Detection Mode
`Next, the description will be given of the speaker detec-
`tion process executed in the speaker detection mode with
`reference to the flowchart shown in FIG. 5. When a user
`connects multiple speakers to the audio system 100 and then
`inputs an instruction by manipulating an input unit (not
`shown), the speaker detection mode is executed. It is noted
`that the speaker detection mode described below is executed
`by the system controller MPU controlling the respective
`components in the signal processing u11it 2. The speaker
`detection process roughly includes a process to measure the
`environmental noise in the sound field such as a listening
`room and another process to determine the existence of the
`speakers thereafter. In the example shown in FIG. 5, these
`processes are executed for each channel.
`When the user instructs the start of the speaker detection
`process, first a variable X indicating the channel number is
`set to “1"’ (step S1). By this, out of the first to eighth speakers
`SPFL to SPSBR shown in FIG. 1, the first speaker SPFL is
`selected.
`Then, the signal processing circuit 2 detects the environ-
`mental noise level of the sound field space such as the
`listening room 7 in which the audio system 100 is installed
`(step S2). Specifically, the microphone 8 collects the ambi-
`ent sounds, and the amplifier 9 and the A/D converter 10
`generate the digital collected sound data DM and supply it
`to the spectnim analyzing unit 11 and the level detecting unit
`12. At this time, the BPF 17 in the eoeflicient operating unit
`30 is set to the through state by which the input signal is
`output as it
`is. The level detecting unit 12 detects the
`environmental noise level from the collected sound data DM
`thus input, and supplies it to the system controller MPU as
`the level data 22. Since the BPF 17 is set to the through state,
`the level data 22 indicates the environmental noise of the
`sound field in all frequency bands.
`The system controller MPU judges whether or not the
`environmental noise level received as the level data 22 is
`smaller than a predetermined first threshold value TH1 (step
`S3). Here, the first threshold value TH1 is a noise level value
`used as a reference to determine whether or not the acoustic
`S/N ratio necessary for executing the speaker detection
`process is maintained.
`
`MS_Biscotti_0061935
`
`

`
`US 6,813,577 B2
`
`'
`
`7
`If the environmental noise level is larger than the first
`threshold level Tl-ll, the system controller MPU judges that
`the sound field is noisy and does not satisfy necessary S/N
`ratio, and executes the spectrum analysis of the environ-
`mental noise (step S4). Namely, the spectrum analyzing unit
`11 divides the collected sound data DM into multiple
`frequency bands, detects sound level of each frequency
`bands, and supplies the level data 21 of each frequency band
`to the system controller MPU (step S4).
`Then,
`the system controller MPU selects an optimum
`frequency band for the speaker detection based on the level
`data 21. The “optimum frequency band” is a frequency band
`silent enough to perform the speaker detection, and specifi-
`cally a frequency band that has an acoustic S/N ratio larger
`than a predetermined reference value. Then,
`the system
`controller MPU determines a second threshold value TH2
`based on the S/N ratio of the selected frequency band, and
`stores the second threshold value TH2 in the memory 15.
`The method of determining the optimum frequency band
`and the second threshold value will be described later in
`detail.
`Further, the system controller MPU generates the control
`signal SF1 to control the characteristics of the band-pass
`filters BPF1 to BPF8 such that the signal of the optimum
`frequency band is passed, and supplies the control signal
`SFl to the respective band-pass filters BPI-'1 to BPFS. The
`system controller MPU also generates the control signal SF2
`to set the pass-band of the band-pass filter 17 to the optimum
`frequency band and supplies the second control signal SF2
`to the band-pass filter 17. The system controller MPU also
`generates the control signal SG to set the gain corresponding
`to the optimum frequency band to the respective variable
`amplifiers ATG1 to ATG8, and supplies them to the variable
`amplifiers ATG1 to ATG8 (step S5). Thus, the band-pass
`filters BPF1 to BPF8 are set to the characteristics to pass the
`signal in the optimum frequency band.
`On the other hand, if the environmental noise level is
`smaller
`than the first
`threshold value TH1,
`the system
`controller Ml-‘U judges that
`the sound field satisfies the
`necessary acoustic S/N ratio for the speaker detection. Then,
`the system controller MPU determines the filter coefficients
`such that all of the band-pass filters BPF1 to BPF8 are set to
`the through state, and supplies the coeffieients to the respec-
`tive band-pass filters BPF1 to BPF8 as the control signal
`SF1. Further,
`the system controller MPU generates the
`control signal SG to set the amplification factors of the
`respective variable amplifies ATG1 to ATG8 to predeter-
`mined gains corresponding to the through state, and supplies
`the control signal SG to the variable amplifiers ATG1 to
`ATG8. The system controller MPU further sets the second
`threshold value TH2 to a predetermined value (step S6).
`In this way, the measurement of the environmental noise
`in the sound field is completed, and then the speaker
`existence judgment is executed.
`The system controller MPU turns the switches SWN and ..
`SW11 ON and turns the other switches OFF. The test signal
`generator 3 generates the test signal DN, and the test signal
`DN is output by the speaker 6FL after passing through the
`band-pass filter BPF1 of the first channel and the variable
`amplifier ATG1. The microphone collects the test sound and
`supplies the collected sound data DM to the level detecting
`unit 12 via the band-pass filter 17 shown in FIG. 4.
`If the judgment in step S3 indicates that the environmental
`noise is smaller than the first
`threshold TH1 (ie, the
`environmental noise is small), the band-pass filter 17 is set
`to the through state in step S6, and the level detecting unit
`12 receives the level data 22 indicating the level of the test
`
`8
`signal in all frequency bands. On the other hand, if the
`judgment in step S3 indicates that the environmental noise
`is larger than the first threshold TH1 (i.e., the environmental
`noise is large), the band-pass filter 17 is set to the optimum
`frequency band in step S4, and hence the level detecting unit
`12 receives only the optimum frequency band component of
`the collected data DM, and supplies the level data 22
`indicating that level to the system controller MPU.
`Then, the system controller MPU compares the received
`level data 22 with the second threshold value TH2 deter-
`mined in step S5 or S6 to judge the existence of the speaker
`(step S8). The detail of the speaker existence judgment
`process is shown in FIG. 7. In FIG. 7, the level data 22 is
`compared with the second threshold value TH2 (step S20).
`If the level data 22 is larger than the second threshold value
`TH2, it is judged that a speaker is connected to the channel
`(step S21). On the contrary, if the level data 22 is smaller
`than the second threshold value TH2, it is judged that no
`speaker is connected to the channel (step S22). Then, the
`process returns to the main routine shown in FIG. 5.
`When the speaker existence for the first channel is thus
`judged, then the system controller MPU stores the judgment
`result in the memory 15 (step S9). Then, the system con-
`troller MPU increments the variable x of the channel number
`by 1 (step S10), and then judges whether or not the variable
`x is larger than the number of the channels (step S11). If the
`variable x is not larger than the channel number, the process
`goes back to step S2 to execute the speaker judgment for the
`next channel (steps S2 to S10). On the other hand, if the
`variable x is larger than the channel number (step S11; Yes),
`the process ends because the speaker existence has already
`been judged for all channels.
`By the speaker detection process described above, if the
`environmental noise is small (more precisely, the S/N ratio
`is large), the test signal of all frequency bands is output, and
`the microphone 8 collects the test sound to judge the
`existence of the speaker. On the other hand, if the environ-
`mental noise is large (more precisely, the S/N ratio is small),
`the speaker existence is judged by using the test signal of the
`optimum frequency band in which the S/N ratio is large
`enough. Therefore, since the speaker judgment is executed
`by using the test signal in the optimum frequency band in
`which the S/N ratio higher than a reference value is
`maintained, the speaker existence may be correctly detected
`automatically even in the sound field having relatively large
`environmental noise.
`In the process shown in FIG. 5, the respective band-pass
`filters BPF1