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Sound source separation system, sound source separation method, and acoustic signal acquisition device

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Sound source separation system, sound source separation method, and acoustic signal acquisition device


A sound source separation system separates a target sound and a disturbance sound coming from an arbitrary direction other than the direction the target sound comes from. The system includes different-directional-signal-group generators and a sensitive region formation unit. The generators each generate two or more combinations of spectra of signals each of which has a different directivity, using received sound signals of microphones. The sensitive region formation unit determines, for each frequency band, whether or not a relationship between powers of the spectra in each combination simultaneously satisfies conditions each defined for each combination, using two or more combinations of the spectra of the signals generated by the respective different-directional-signal-group generators, and performs multidimensional band selection of assigning power of a spectrum selected beforehand to a spectrum of the target sound to be separated, for a frequency band where the conditions are simultaneously satisfied.

Browse recent Waseda University patents - Tokyo, JP
Inventors: Tetsunori KOBAYASHI, Kenzo AKAGIRI, Satoshi KANBA
USPTO Applicaton #: #20120308039 - Class: 381 92 (USPTO) - 12/06/12 - Class 381 
Electrical Audio Signal Processing Systems And Devices > Directive Circuits For Microphones

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The Patent Description & Claims data below is from USPTO Patent Application 20120308039, Sound source separation system, sound source separation method, and acoustic signal acquisition device.

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TECHNICAL FIELD

The present invention relates to a sound source separation system, a sound source separation method and an acoustic signal acquisition device which separate a target sound and a disturbance sound coming from an arbitrary direction other than a direction in which the target sound comes from, and is available for a case where a desired speech is acquired through a portable device like a cellular phone, and an in-vehicle device like a car navigation system.

BACKGROUND ART

In normal voice recognition, a speech uttered from a mouth is recorded through a close-talking type microphone, and is subjected to a recognition process. On the other hand, there are lots of applications, such as interaction with a robot, operation of an in-vehicle device like a car navigation system through a speech, and creation of conference minutes, where enforcing a user to use a close-talking type microphone is unnatural. In such applications, it is desirable that a speech should be recorded through a microphone provided at a system side and should be subjected to a recognition process. In a case where speech recording and voice recognition are performed through a microphone provided away from an utterer, however, an S/N ratio is deteriorated, it is difficult to hear, and the accuracy of voice recognition is extremely reduced.

In response to such problems, there is an attempt that a desired speech is selectively recorded by controlling the directivity using a microphone array. As such devices which control the directivity using a few microphones, there are an ultra directional microphone using two single-directional microphone units (see, patent literature 1) and a recording device for multi-channel stereo using four non-directional microphones (see, patent literature 2). Further, there is a microphone device having three pairs of microphones disposed around a base microphone (see, patent literature 3).

Moreover, there is proposed a scheme called SAFIA which separates a sound by utilizing a difference between sound pressures, reaching individual microphones and caused due to differences in positional relationships between the individual microphones and a sound source (see, patent literature 4). The scheme called SAFIA is a sound separation technique which causes output signals of a plurality of fixed microphones to undergo narrow-band spectrum analysis, and for a microphone that gives the largest power for each frequency band, performs band selection of assigning a sound of that frequency band to that microphone (see FIG. 8 to be discussed later). Patent Literature 1: Japanese Unexamined Patent Publication No. H10-126876 (claim 1, FIGS. 1 and 2, and abstract) Patent Literature 2: Japanese Unexamined Patent Publication No. 2002-223493 (claim 1, FIGS. 1 and 3, and abstract) Patent Literature 3: Japanese Unexamined Patent Publication No. 2002-271885 (claim 1, FIGS. 1 and 11, and abstract) Patent Literature 4: Japanese Patent Publication No. 3355598 (paragraphs 0006, 0007, FIG. 1 and abstract)

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

It is, however, difficult to sufficiently separate a desired speech from background noises by merely controlling the directivity through a microphone array, and to miniaturize the device. According to the ultra directional microphone disclosed in patent literature 1 and the recording device for multi-channel stereo disclosed in patent literature 2, controlling of the directivity is realized by a few microphones, miniaturization of the device may be possible, but a performance of separating a desired sound is not good enough. Further, the microphone device disclosed in patent literature 3 uses a total of seven microphones, so that it has the same problems as those of the microphone array.

According to the foregoing SAFIA disclosed in patent literature 4, band selection is performed by utilizing a difference between sound pressure levels of signals between microphones originating from positional relationships of a plurality of fixed microphones, but in performing band selection, unlike the present invention to be discussed later, directivity control appropriate for separation of a desired speech and noises is not performed, so that the separation performance thereof is not good enough. Note that only a separation process (see FIG. 8 to be discussed later) through band selection not including a generation process of a spectrum of a target subject to a separation process through band selection in the scheme called SAFIA will be hereinafter described as maximum level band selection (BS-MAX). According to the maximum level band selection (BS-MAX) performed in the SAFIA, powers of the same frequency band are compared for each frequency band between spectra subject to comparison, and band selection of assigning the largest power at individual frequency bands to a spectrum obtained by separation is performed, but according to the invention, in addition to performing such a maximum level band selection (BS-MAX), powers at the same frequency band are compared for each frequency band between spectra subject to comparison, and band selection of assigning the smallest powers at individual frequency bands to a spectrum obtained by separation is also performed, and this will be described as minimum level band selection (BS-MIN). Further, according to the present invention, not only it is determined whether or not one condition such as selecting the maximum or the minimum power is satisfied, but also it is determined whether or not a plurality of conditions are satisfied simultaneously, and this will be described as a multidimensional band selection (BS-multiD), and the case of two conditions will be described as a two-dimensional band selection (BS-2D), and the case of three conditions will be described as a three-dimensional band selection (BS-3D).

It is an object of the invention to provide a sound source separation system, a sound source separation method and an acoustic signal acquisition device which can accurately separate a target sound and a disturbance sound coming from an arbitrary direction, and enables miniaturization of a device.

Means for Solving the Problems

<<Invention of a Sound Source Separation System>>

<Two Microphones Type Invention> Invention of a Type that Two Microphones Are Used

According to the invention, a sound source separation system that separates a target sound and a disturbance sound coming from an arbitrary direction other than a direction in which the target sound comes from and comprises: two microphones disposed in such a manner as to be spaced away from each other; a target sound superior signal generator which performs a linear combination process for emphasizing the target sound using received sound signals of the two microphones on a time domain or a frequency domain to generate at least one target sound superior signal; a target sound inferior signal generator which performs a linear combination process for suppressing the target sound using the received sound signals of the two microphones on a time domain or a frequency domain to generate at least one target sound inferior signal to be paired with the target sound superior signal; and a separator which separates the target sound and the disturbance sound from each other using a spectrum of the target sound superior signal generated by the target sound superior signal generator or obtained by a subsequent frequency analysis and a spectrum of the target sound inferior signal generated by the target sound inferior signal generator or obtained by a subsequent frequency analysis.

“A sound source separation system that separates a target sound and a disturbance sound coming from an arbitrary direction other than a direction in which the target sound comes from” means a system that can perform sound source separation in a case where a direction in which the disturbance sound comes from is not specified, other than a case where both directions in which the target sound and the disturbance sound come from are already known, like a case where sound source separation is performed through independent component analysis (ICA). Moreover, “a disturbance sound coming from an arbitrary direction other than a direction in which the target sound comes from” does not always mean all directions in 360 degrees other than the direction in which the target sound comes from, but may be an arbitrary direction in a range other than the direction in which the target sound comes from and the adjacent directions, and for example, when θ=0 degree is the direction in which the target sound comes from, only a range of θ=−90 to 90 degrees may be a separation target range, and in short, the disturbance sound comes from an unspecified direction. The same is true on other inventions.

“Performing a linear combination process for emphasizing the target sound using received sound signals of the two microphones on a time domain or a frequency domain” and “performing a linear combination process for suppressing the target sound using the received sound signals of the two microphones on a time domain or a frequency domain” include (1) performing linear combination processes for emphasizing and suppressing the target sound using the received sound signals of the two microphones as signals on a time domain, and generating a target sound superior signal and a target sound inferior signal as signals on a time domain, and (2) performing frequency analysis on the received sound signals (signals on a time domain) of the two microphones to make signals on a frequency domain (spectra), performing linear combination processes for emphasizing and suppressing the target sound, and generating a target sound superior signal and a target sound inferior signal as signals (spectra) on a frequency domain. The same is true on other inventions.

Further, when the target sound superior signal generated by the target sound superior signal generator is a signal on a frequency domain, “a spectrum of the target sound superior signal generated by the target sound superior signal generator or obtained by a subsequent frequency analysis” is that signal itself and is a signal on a frequency domain obtained by frequency analysis of that signal when the target sound superior signal obtained by the target sound superior signal generator is a signal on a frequency domain. The same is true on “a spectrum of the target sound inferior signal generated by the target sound inferior signal generator or obtained by a subsequent frequency analysis”. The same is true on other inventions.

The “linear combination process” includes a process of acquiring a sum or a difference, and a process of multiplying a coefficient. The same is true on other inventions.

“Separating the target sound and the disturbance sound” using “the spectrum of the target sound superior signal” and “the spectrum of the target sound inferior signal” includes, for example, a process for each frequency band, i.e., a process of using both powers of the spectrum of the target sound superior signal and the spectrum of the target sound inferior signal at the same frequency band. The same is true on other inventions. The same process can be performed when amplitude values at the same frequency band are used, so that a process using powers represents both processes in the specification.

“The target sound” and “the disturbance sound” are mainly speeches of a human, but include, for example, a music, an animal call, natural sounds, such as a thunder, a ripping wave, and a murmur, various sound effects, such as a buzzer, an alarm sound, a honker, and an alarm whistle, and various mechanical sounds, such as a sound from a road, running sound of a vehicle, a takeoff sound of an airplane, and an operational sound of a machine. The same is true on other inventions.

According to the sound source separation system of such an invention, linear combination processes of emphasizing the target sound and suppressing the target sound are performed on a time domain or a frequency domain using the received sound signals of the two microphones to generate the target sound superior signal and the target sound inferior signal, so that controlling of the directivity appropriate for separation of the target sound and the disturbance sound becomes possible.

Because a separation process is performed using the spectrum of the target sound superior signal and the spectrum of the target sound inferior signal both generated by controlling the directivity, the target sound and the disturbance sound are precisely separated from each other. Accordingly, in comparison with the case of patent literature 4 where band selection is performed utilizing a sound-pressure difference of signals between the microphones originating from the positional relationships of the plurality of microphones, the separation performance can be improved.

The directivity is controlled by performing linear combination processes of emphasizing and suppressing the target sound, so that a sound coming from an unspecific direction can be separated unlike the case of a separation process utilizing independent component analysis (ICA) which separates only a sound coming from a specific direction.

The number of microphones to be used is two, and sound source separation can be realized by a few microphones, so that miniaturization of a device becomes possible, thereby achieving the foregoing object.

<Invention of a Type that Two Microphones are Disposed in Parallel with a Direction in which the Target Sound Comes from> Invention of a Type that Two Microphones are Disposed in the Direction in which the Target Sound Comes from or in an Approximately Same Direction as that Direction

To be more precise, it is possible to employ the following structure. That is, in the foregoing sound source separation system, the two microphones may be disposed side by side in the direction in which the target sound comes from or an approximately same direction as that direction, the target sound superior signal generator may acquire a difference between a received sound signal of one microphone disposed near a sound source of the target sound in the two microphones and a received sound signal of an other microphone disposed away from the sound source of the target sound on a time domain or a frequency domain, and the target sound inferior signal generator may acquire a difference between the received sound signal of the one microphone undergone a delayed process and the received sound signal of the other microphone on a time domain or a frequency domain (e.g., the case shown in FIG. 1 to be discussed later).

“Acquiring a difference between the received sound signal of the one microphone undergone a delayed process and the received sound signal of the other microphone on a time domain or a frequency domain” includes (1) after performing a delayed process on the received sound signal (signal on a time domain) of the one microphone on a time domain, acquiring a difference between the signal (signal on a time domain) undergone a delayed process and the received sound signal (signal on time domain) of the other microphone, and generating a signal on a time domain, (2) performing frequency analysis on both received sound signals (signals on a time domain) of the one and other microphones to generate signals (spectra) on a frequency domain, after performing a delayed process on the spectrum of the received sound signal of the one microphone on a frequency domain, acquiring a difference between the spectrum undergone the delayed process and the spectrum of the received sound signal of the other microphone, and generating a signal on a frequency domain, and (3) performing a delayed process on a received sound signal (signal on a time domain) of the one microphone on a time domain, performing frequency analysis on the signal undergone a delayed process (signal on a time domain) to generate a signal on a frequency domain (spectrum), and after performing frequency analysis on the received sound signal (signal on a time domain) of the other microphone to generate a signal on a frequency domain (spectrum), acquiring a difference between the spectrum of the received sound signal of the one microphone undergone a delayed process and the spectrum of the received sound signal of the other microphone, and generating a signal on a frequency domain. The same is true on other inventions.

In a case where the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction as that direction, the separator may compare powers at a same frequency band between the spectrum of the target sound superior signal and the spectrum of the target sound inferior signal for each frequency band, and perform band selection (maximum level band selection: BS-MAX) of assigning larger powers at the individual frequency bands to a spectrum obtained by separation.

“Assigning power to a spectrum obtained by separation” means that when the power of the spectrum of the target sound superior signal is large, for the frequency band thereof, the larger power is assigned to the spectrum of the target sound, and when the power of the spectrum of the target sound inferior signal is large, for the frequency band thereof, the larger power is assigned to the spectrum of the disturbance sound (see FIG. 8 to be discussed later). The same is true on other inventions.

In a case where the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction as that direction, the separator may perform spectral subtraction of subtracting a value, obtained by multiplying power of the spectrum of the target sound inferior signal by a coefficient, from power of the spectrum of the target sound superior signal at a same frequency band.

The “coefficient” is a coefficient depending on, for example, the largeness of a difference between the power of the target sound superior signal and the power of the target sound inferior signal. The same is true on other inventions when spectral subtraction is performed.

In a case where the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction as that direction, it is preferable that a target sound to be separated should be changed over to a target sound in a normal mode and a target sound in a changeover mode coming from a direction opposite to the normal mode target sound, the one microphone should be disposed near a sound source of the normal mode target sound and the other microphone should be disposed away from the sound source of the normal mode target sound in the normal mode, the other microphone should be disposed near a sound source of the changeover mode target sound and the one microphone should be disposed away from the sound source of the changeover mode target sound in the changeover mode, and the target sound inferior signal generator should comprise: a first target sound inferior signal generation unit which acquires a difference between the received sound signal of the one microphone undergone a delayed process and the received sound signal of the other microphone on a time domain or a frequency domain; a second target sound inferior signal generation unit which acquires a difference between the received sound signal of the other microphone undergone a delayed process and the received sound signal of the one microphone on a time domain or a frequency domain; and a changeover unit which changes over a first target sound inferior signal for the normal mode generated by the first target sound inferior signal generation unit and a second target sound inferior signal for the changeover mode generated by the second target sound inferior signal generation unit as the target sound inferior signal to be processed by the separator.

In a case where changeover of a mode between the normal mode and the changeover mode is possible, it is possible to change over the direction of the target sound to be acquired without changing the position of the two microphones, thereby improving the usability of the system.

In a case where the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction as that direction, the target sound inferior signal generator may apply a time delay which is a same as or an approximately same as a sound wave propagation time between the two microphones to the received sound of the microphone subject to the delayed process on a time domain or a frequency domain (see, FIGS. 4 and 7).

In a case where it is structured in such a way that a time delay which is the same as or an approximately same as the sound wave propagation time between the two microphones is applied, a directivity such that the amplitude value of the target sound inferior signal becomes zero can be created in the direction in which the target sound comes from (in the case of FIG. 7, for example, θ=0 degree for the target sound in the normal mode, and θ=180 degree (−180 degree) for the target sound in the changeover mode), a difference of an amplitude value with the directivity (directivity originating from the target sound superior signal) directed toward the target sound can be large.

In a case where the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction as that direction, the target sound inferior signal generator may apply a time delay which is shorter than a sound wave propagation time between the two microphones to the received sound of the microphone subject to the delayed process on a time domain or a frequency domain (see, FIG. 30).

In a case where it is structured in such a way that a time delay which is shorter than the sound wave propagation time between the two microphones is applied, a directivity that expands a range where the amplitude value of the target sound inferior signal is suppressed can be created in the vicinity of the direction in which the target sound comes from (in the case of FIG. 30, for example, θ=0 degree for the target sound in the normal mode, and θ=180 degree (−180 degree) for the target sound in the changeover mode), so that it becomes possible to expand a range where a difference of an amplitude value with the directivity (directivity of the target sound superior signal) directed toward the target sound.

In a case where the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction as that direction, it is possible to employ a structure such that the two microphones are respectively provided at a corresponding portion of a front face of a portable device at which an operation unit and/or a screen display unit is provided and a corresponding portion of a rear face opposite thereto.

The “portable device” includes, for example, a cellular phone (including a PHS), or a portable information terminal (PDA).

A “corresponding portion” means a directly opposite portion as viewed from each other.

In a case where the two microphones are respectively provided at the front and rear face of the portable device, the portable device may be a foldable cellular phone which is folded and closed when not in use and opened when in use, and it is possible to employ a structure such that a clearance between the two disposed microphones changes in accordance with an opening/closing operation of the cellular phone, and a clearance when the cellular phone is opened is larger than a clearance when the cellular phone is closed.

“Changing in accordance with an opening/closing operation” includes, for example, causing the microphone provided at the front face side to be retained when the portable device is closed, and causing the microphone to automatically protrude outwardly when opened, or causing the microphone provided at the rear face side to be retained when closed, and causing that microphone to automatically protrude outwardly when opened, and the combination thereof. For example, the microphone provided at the front face side of a cellular phone is urged outwardly by an elastic member, such as a spring or a rubber, and when the cellular phone is folded and closed, the microphone is pressed by an opposing surface (a surface constituting a face and becoming an opposing surface when folded) of the cellular phone, the elastic member is compressed and the microphone is retained, and when the cellular phone is opened, the microphone is caused to protrude outwardly by force of the elastic member returning to an original state, and such an operation may be realized by various mechanisms using a gear, cam, a belt, and a linkage, a mechanism using an air pressure or an oil pressure, and an electrical mechanism using a motor or the like. The same is true on other inventions that the microphones are disposed on both front and rear faces.

In a case where the two microphones are respectively provided at the front and rear face of the portable device, it is possible to employ a structure such that the two microphones are provided at end portions of both sides of a rotation support member attached in such a manner as to be rotatable around an axis parallel to the front/rear face of the cellular phone, and the rotation support member is retained in a state parallel to or approximately parallel to the front/rear surface of the cellular phone when not in use, and becomes orthogonal or approximately orthogonal to the front/rear face of the cellular phone when in use (e.g., the case shown in FIG. 29 to be discussed later).

As mentioned above, a mode can be changed over to the normal mode and the changeover mode when the target sound inferior signal generator is structured in such a manner as to include the first target sound inferior signal generator and the second target sound inferior signal generator and a changeover unit (e.g., the case shown in FIG. 1 to be discussed later), a process corresponding to a process executed by the first target sound inferior signal generator may be a process executed by the target sound inferior signal generator, and a process corresponding to a process executed by the second target sound inferior signal generator may be a process executed by the target sound superior signal generator. In this case, however, it is preferable that adjustment of multiplying the value of a signal obtained by at least one process by a coefficient should be performed. That is, the target sound superior signal generator may acquire a difference between the received sound signal of the other microphone undergone a delayed process and the received sound signal of the one microphone on a time domain or a frequency domain, (executing a process corresponding to a process executed by the second target sound inferior signal generator), and the target sound inferior signal generator may acquire a difference between the received sound signal of the one microphone undergone a delayed process and the received sound signal of the other microphone on a time domain or a frequency domain (executing a process corresponding to a process executed by the first target sound superior signal generator), and in this case, it is preferable that at least one difference in the difference obtained by the target sound superior signal generator and the difference obtained by the target sound inferior signal generator should be multiplied by a coefficient, and the difference obtained by the target sound superior signal generator should be set relatively smaller than the difference obtained by the target sound inferior signal generator (e.g., the case shown in FIG. 27).

When the foregoing structure is taken as the normal mode, the changeover mode can be structured as follows. That is, the target sound superior signal generator may acquire a difference between the received sound signal of the one microphone undergone a delayed process and the received sound signal of the other microphone on a time domain or a frequency domain (executing a process corresponding to a process executed by the first target sound inferior signal generator), and the target sound inferior signal generator may acquire a difference between the received sound signal of the other microphone undergone a delayed process and the received sound signal of the one microphone on a time domain or a frequency domain (executing a process corresponding to a process executed by the second target sound inferior signal generator), and in this case, it is preferable that at least one difference in the difference obtained by the target sound superior signal generator and the difference obtained by the target sound inferior signal generator should be multiplied by a coefficient, and the difference obtained by the target sound superior signal generator should be set relatively smaller than the difference obtained by the target sound inferior signal generator (e.g., the case shown in FIG. 28).

<Invention of a Type that the Two Microphones are Disposed in a Direction Orthogonal to the Direction in which the Target Sound Comes from and Sum/Difference are Both Acquired> Invention of a Type that the Two Microphones are Disposed Side by Side in a Direction Orthogonal to or Approximately Orthogonal to the Direction in which the Target Sound Comes from, and a Sum and Difference of Received Sound Signals are Used

In addition to the structure that the two microphones are disposed side by side in the direction in which the target sound comes from or in an approximately same direction, the following structure can be employed. That is, in the foregoing sound source separation system, the two microphones are disposed side by side in a direction orthogonal to or approximately orthogonal to the direction in which the target sound comes from, the target sound superior signal generator acquires a sum of the received sound signals of the two microphones on a time domain or a frequency domain, and the target sound inferior signal generator acquires a difference between the received sound signals of the two microphones on a time domain or a frequency domain (e.g., the case shown in FIG. 9 to be discussed later).

In a case where the two microphones are disposed side by side in a direction orthogonal to or approximately orthogonal to the direction in which the target sound comes from, and a sum of the received sound signals of the two microphones are acquired to generate the target sound superior signal, the separator may multiply at least one spectrum in the spectrum of the target sound superior signal and the spectrum of the target sound inferior signal by a coefficient depending on a frequency, compare powers of the spectra at a same frequency band, and perform band selection of assigning larger powers at the individual frequency bands to a spectrum obtained by separation (maximum level band selection: BS-MAX).

In a case where the two microphones are disposed side by side in a direction orthogonal to or approximately orthogonal to the direction in which the target sound comes from, and a sum of the received sound signals of the two microphones are acquired to generate the target sound superior signal, the separator may perform spectral subtraction of subtracting a value, obtained by multiplying power of the spectrum of the target sound inferior signal by a coefficient, from power of the spectrum of the target sound superior signal at a same frequency band.

<Invention of a Type that Two Microphones are Disposed in a Direction Orthogonal to the Direction in which the Target Sound Comes from and a Difference is Acquired> Invention of a Type that the Two Microphones are Disposed Side by Side in a Direction Orthogonal to or Approximately Orthogonal to the Direction in which the Target Sound Comes from and a Difference Between the Received Sound Signals is Used but a Sum Thereof is Not Used



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stats Patent Info
Application #
US 20120308039 A1
Publish Date
12/06/2012
Document #
13486798
File Date
06/01/2012
USPTO Class
381 92
Other USPTO Classes
International Class
04R3/00
Drawings
50



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