This application claims priority to Japanese Patent Application No. 2013-025244 filed on Feb. 13, 2013. The entire disclosure of Japanese Patent Application No. 2013-025244 is hereby incorporated herein by reference.
1. Field of the Invention
This invention generally relates to a voice input device. This invention also relates to a noise suppression method applied to a voice input device.
2. Background Information
Generally, voice input devices are conventionally well known in the art. The voice input devices allow voice to be inputted and execute signal processing on the inputted voice. For example, voice input devices are applied to portable telephones, headsets, and other such voice communication devices, information processing systems that make use of technology for analyzing inputted voice (such as voice authentication systems, voice recognition systems, command generation systems, electronic dictionaries, translators, and voice input remote controls), recording devices, and so forth.
A voice input device such as this generally ends up taking in noise (e.g., background noise) generated at a distance, such as ambient noise or voices of other people, in addition to sound emitted from the intended sound source (such as a speaker's voice). If background noise is taken in, the result is that it a listener can find it difficult to hear a speaker's voice, leading to problems such as erroneous voice recognition.
Because of this, various methods for reducing noise have been disclosed in the past. For instance, Patent Literature 1 (Japanese Unexamined Patent Application Publication H7-193548) discloses a configuration in which control signals are formed and the details of the noise reduction processing are changed according to the detected noise level. With a configuration such as this, the amount of noise reduction can be appropriately adjusted, so a more natural reproduced sound is obtained.
With the noise reduction processing method disclosed in Patent Literature 1, information that has been stored ahead of time (e.g., information related to noise) is used to execute noise reduction processing. Therefore, it has been discovered that the noise reduction processing will not be carried out properly if, for example, some unexpected noise should be taken in. Also, it has been discovered that there is the risk that the job will be made more difficult because a large quantity of information has to be stored in advance.
One object is to provide a voice input device with which background noise generated at a distance can be accurately suppressed. Also, another object is to provide a noise suppression method applied to the voice input device.
In view of the state of the known technology, a voice input device is provided that includes a first microphone, a second microphone, and a processor. The second microphone has a lower distance decay rate than the first microphone. The processor is configured to acquire noise information of noise by comparing a first signal obtained from the first microphone with a second signal obtained from the second microphone. The processor is further configured to perform noise suppression processing based on the noise information.
Also other objects, features, aspects and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses one embodiment of the voice input device and the noise suppression method.
Referring now to the attached drawings which form a part of this original disclosure:
Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Referring to
Referring now to
The speaker component 12 outputs sound by converting electrical signals into physical vibrations. The microphone unit 13 converts inputted sound into electrical signals, and outputs the result. The detailed configuration of the microphone unit 13 will be discussed below. The interface component 14 is provided so that the user can operate the headset 1, and includes, for example, a power switch 14a (see
Referring now to
Also, a first opening 131b is formed in the approximate center of the upper face of the substrate component 131 (the face on the side where the cover component 132 is installed). The first opening 131b is substantially circular in plan view. A second opening 131c is formed on the other end (the opposite side from the side where the through-hole 131a is formed) in the lengthwise direction of the lower face of the substrate component 131 (see
The substrate component 131 with this configuration can be formed by superposing a plurality of (such as three) substrates, although this is not intended to be particularly limiting.
As shown in
As shown in
The two MEMS chips 21 and 23 and the two ASICs 22 and 24 are joined with a die bonding material (such as an epoxy or silicone resin-based adhesive) on the substrate component 131. The two MEMS chips 21 and 23 are joined on the substrate component 131 so that there will be no gap between their bottom faces and the upper face of the substrate component 131, in order to prevent acoustic leakage. The first MEMS chip 21 is electrically connected by a wire 25 (preferably a gold wire) to the first ASIC 22. Also, the second MEMS chip 23 is electrically connected by a wire 25 (preferably a gold wire) to the second ASIC 24.
The first ASIC 22 is electrically connected by wires 25 to a plurality of electrode terminals 26a, 26b, and 26c formed on the upper face of the substrate component 131. The electrode terminal 26a is a power supply terminal for inputting power supply voltage (VDD). The electrode terminal 26b is a first output terminal for outputting electrical signals that have been amplified by the first ASIC 22. The electrode terminal 26c is a ground terminal for making a ground connection.
Similarly, the second ASIC 24 is electrically connected by wires 25 to a plurality of electrode terminals 27a, 27b, and 27c formed on the upper face of the substrate component 131. The electrode terminal 27a is a power supply terminal for inputting power supply voltage (VDD). The electrode terminal 27b is a second output terminal for outputting electrical signals that have been amplified by the second ASIC 24. The electrode terminal 27c is a ground terminal for making a ground connection.
The electrode terminals 26a and 27a are electrically connected via wiring (not shown; includes through-wiring) to an external connection-use power supply pad 28a (see
A sealing-use pad 28e (see
Returning to
As shown in
A plurality of through-holes are formed in the fixed electrode 21b of the first MEMS chip 21, allowing sound waves to pass through the fixed electrode 21b. In the following description, the through-hole 131a will be referred to as a first sound hole, and the second opening 131c as a second sound hole, focusing on their functions.
Similarly, the second ASIC 24 includes a charge pump circuit 241 and an amplifier circuit 242. The charge pump circuit 241 applies bias voltage to the second MEMS chip 23. The amplifier circuit 242 detects changes in the electrostatic capacity and outputs (OUT2) the amplified electrical signal. The amplification gain of the two amplifier circuits 222 and 242 can be set as needed, and the gain settings can be different.
When sound is generated outside the microphone unit 13, the sound waves inputted from the first sound hole 131a go through a first sound channel 29 and arrive at the upper face of the diaphragm 21a of the first MEMS chip 21. The sound waves inputted from the second sound hole 131c go through a second sound channel 30 and arrive at the lower face of the diaphragm 21a of the first MEMS chip 21 (see
Also, when sound is generated outside the microphone unit 13, the sound waves inputted from the first sound hole 131a go through the first sound channel 29 and arrive at the upper face of the diaphragm 23a of the second MEMS chip 23 (see
As can be understood from the above, with the microphone unit 13, signals obtained using the first MEMS chip 21 and signals obtained using the second MEMS chip 23 are outputted separately to the outside. In other words, the microphone unit 13 is configured to include two microphones in a single package. The first microphone utilizing the first MEMS chip 21 (corresponds to the first microphone of the present invention), and the second microphone utilizing the second MEMS chip 23 (corresponds to the second microphone of the present invention) have the following different characteristics.
Before describing the differences in the characteristics of the two microphones, the properties of sound waves will be described in simple terms.
P=k/R (1)
As is clear from
In contrast, the sound pressure exerted on the diaphragm 21a will be lowest (0) when the sound source is at 90° or 270°. This is because the difference between the distance from the first sound hole 131a until the sound waves reach the upper face of the diaphragm 21a and the distance from the second sound hole 131c until the sound waves reach the lower face of the diaphragm 21a is substantially zero. Specifically, the first microphone is bidirectional, with high sensitivity to sound waves incident from a direction of 0° or 180°, and low sensitivity to sound waves incident from a direction of 90° or 270°.
With the first MEMS chip 21, the diaphragm 21a vibrates due to the difference in the sound pressure exerted on its two sides (upper and lower faces). With the second MEMS chip 23, on the other hand, the diaphragm 23a vibrates due to the sound pressure exerted on one side (the upper face). With the second MEMS chip 23, the sound pressure level decays in inverse proportion to the distance (1/R, where R is the distance). With the first MEMS chip 21, on the other hand, the sound pressure level decays at 1/R2. Accordingly, as shown in
Because it has the distance decay characteristics discussed above, the first microphone (differential microphone) utilizing the first MEMS chip 21 efficiently picks up sound generated near this microphone, but tends not to pick up background noise. That is, the first microphone functions as what is known as a close microphone. On the other hand, the second microphone utilizing the second MEMS chip 23 has the property of broadly picking up sound, even sound whose source is located farther away from this microphone.
The characteristics of the first microphone will now be described further. The sound pressure of the targeted sound generated near the first microphone (the microphone unit 13) decays more between the first sound hole 131a and the second sound hole 131c. Therefore, in the sound pressure of the targeted sound generated near the first microphone, a large difference occurs between the sound pressure at the upper face of the diaphragm 21a and the sound pressure at the lower face. Background noise, meanwhile, has a sound source that is located farther away than the target sound, so there is less decay between the first sound hole 131a and the second sound hole 131c. Accordingly, for background noise, there is a smaller difference between the sound pressure at the upper face of the diaphragm 21a and the sound pressure at the lower face. Here, we are assuming a case in which the distance from the sound source to the first sound hole 131a is different from the distance from the sound source to the second sound hole 131c.
Since there is little difference in the sound pressure of background noise received at the diaphragm 21a, the sound pressure of background noise is substantially cancelled out at the diaphragm 21a. By contrast, the sound pressure of the above-mentioned target sound is not cancelled out at the diaphragm 21a because there is the above-mentioned large difference in sound pressure of the target sound received at the diaphragm 21a. Therefore, the first microphone utilizing the first MEMS chip 21 has excellent performance in reducing the amount of background noise that is picked up, for target sound generated nearby.
Taking into account the above microphone characteristics, with the headset 1 (a close-talking voice input device), the signal outputted from the first microphone (close microphone) utilizing the first MEMS chip 21 is basically utilized as a voice signal of the speaker's voice. This does not mean, however, that background noise is completely eliminated by the first microphone. In view of this, the configuration is such that the second microphone utilizing the second MEMS chip 23 is utilized to further suppress the background noise component included in the signal outputted from the first microphone. The noise suppression function with which the headset 1 is equipped will now be described.
Referring now to
Background noise generated separately from the speaker's voice occurs relatively far away (such as at least 250 mm from the microphone location). As discussed above, the sensitivity to background noise generated at a distance is different between the first microphone and second microphone. Specifically, the second microphone has considerably better sensitivity to background noise than the first microphone. Accordingly, when background noise occurs, the gain differential (Δg) between the first microphone and second microphone is greater than the above-mentioned ΔG.
Actually, however, it is conceivable, for example, that the distance from the sound source (the mouth of the speaker) to the position of the microphone unit 13 will include a certain amount of error. Therefore, in the illustrated embodiment a threshold is determined that includes an allowance α determined by taking into account this error, etc., and the distance decay characteristics (an example of which is shown in
Δg≧ΔG+α (2)
The allowance α can also be selected by the user. There are users who are not expected to need background noise to be suppressed, because they want to hear speech in as natural a sound as possible, or for some other such reason, as well as users who want all of the background noise to be eliminated. The various needs of different users can be easily accommodated by readying a plurality of stages for the allowance α.
As can be seen from
If the frequency band in which background noise is being generated has been identified, noise suppression can be carried out by performing processing to remove signals of that frequency band, or reduce the signal strength. Therefore, in this embodiment, the controller 11 (see
The signal outputted by the first microphone and the signal outputted by the second microphone are both outputted to the controller 11 (see
In this embodiment, the configuration is such that FFT processing is executed on the signal outputted from the first microphone and on the signal outputted from the second microphone. However, this processing can instead be discrete Fourier transform (DFT). The first signal obtained by subjecting the signal outputted from the first microphone to FFT (or DFT) processing corresponds to the first signal of the present invention. The second signal obtained by subjecting the signal outputted from the second microphone to FFT (or DFT) processing corresponds to the second signal of the present invention.
When FFT (or DFT) processing is executed, the controller 11 compares the first signal and the second signal at each frequency. More precisely, the controller 11 calculates the difference (Δg; absolute value) in signal strength between the first signal and the second signal for each frequency (step S3). The controller 11 then checks whether or not there is a frequency that satisfies the above-mentioned formula (2) (i.e., Δg≧ΔG+α), from the obtained difference (Δg) in signal strength (step S4).
If there is a frequency that satisfies the formula (2) (Yes in step S4), then the controller 11 concludes (identifies) that noise is included in that frequency. In the example shown in
When filtering is executed, the controller 11 controls the communication component 17 to send the filtered signal to the transmission destination (the partner communicating with the headset 1 (step S6). If there is no frequency that satisfies the formula (2) (No in step S4), the controller 11 concludes that the sound signal inputted to the first microphone does not include any noise. Therefore, the signal (first signal) is sent to the transmission destination without undergoing the filtering of step S5.
This filtering will now be described in a bit more detail.
A plurality of types of configuration can be readied for the waveform of the filtering, and the user can select the appropriate one. This makes it possible to use the headset 1 in a way that suits the preferences of the user.
The headset 1 in this embodiment includes a noise suppression function as described above (a function of suppressing noise included in speech picked up by the microphones). Accordingly, with the headset 1 in this embodiment, background noise can be accurately eliminated without storing numerous noise patterns ahead of time.
The embodiment given above is an example of the present invention, and the applicable scope of the present invention is not limited to or by the configuration of the embodiment given above. Naturally, the above embodiment can be suitably modified without exceeding the technological concept of the present invention.
For example, the configuration of the microphone unit 13 given above is just one example, and various modifications are possible. For instance, in the above configuration, the sound holes 131a and 131c of the microphone unit 13 are provided on the substrate component 131 side. However, the configuration can instead be such that the sound holes of the microphone unit 13 are provided on the cover component 132 side, for example.
Also, in the illustrated embodiment, the microphone unit 13 includes the first microphone (close microphone) and the second microphone (non-directional microphone) in a single package. However, the first microphone and second microphone do not need to be configured within a single package, and can be configured separately.
Also, in the illustrated embodiment, the first microphone is configured as a differential microphone converting input sound into electrical signals by vibrating the single diaphragm based on the differential in sound pressure exerted on the two sides of the single diaphragm. However, the first microphone can be configured as a differential microphone having a plurality of diaphragms.
Also, in the illustrated embodiment, the signal filtered when background noise occurred is the signal obtained from the first microphone (close microphone). The present invention, however, is not limited to this configuration. The signal filtered when background noise occurs can be the signal obtained from the second microphone (non-directional microphone).
Also, in the illustrated embodiment, the present invention is applied to the headset, but the present invention is not limited to the headset. The present invention can instead be applied to a portable telephone or another such speech communication device, an information processing system (such as a voice recognition system or a translator), a recording device, or the like.
In the illustrated embodiment, the controller 11 preferably includes a microcomputer with a control program that controls the various components as discussed above. The controller 11 can include other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The microcomputer of the controller 11 is programmed to control the various components. The internal RAM of the controller 11 can stores statuses of operational flags and various control data. The internal ROM of the controller 11 can stores programs for various operations. The controller 11 is capable of selectively controlling any of the components of the headset 1. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the controller 11 can be any combination of hardware and software that will carry out the functions.
In the illustrated embodiment, a voice input device includes a first microphone, a second microphone, and a processor. The second microphone has a lower distance decay rate than the first microphone. The processor is configured or programmed to acquire noise information of noise by comparing a first signal obtained from the first microphone with a second signal obtained from the second microphone. The processor is further configured or programmed to perform noise suppression processing based on the noise information.
With this configuration, the noise is suppressed by acquiring the noise information by comparing signals obtained from two microphones with different distance decay rates. Therefore, less data needs to be readied in advance in order to suppress the noise, and the noise suppression can be carried out more accurately.
With the voice input device, the noise information can be information related to frequencies of the noise (e.g., frequencies included in the noise). The noise suppression processing can include performing filtering to suppress signal strength of the frequencies of the noise. With this configuration, for example, the noise information can be simply acquired by utilizing fast Fourier transform processing or the like, and the noise can be suppressed by utilizing digital processing.
With the voice input device, the processor can be further configured or programmed to identify the frequencies of the noise by comparing the magnitude relation between a specific threshold and an error amount between signal strength of the first signal and signal strength of the second signal. With this configuration, the specific threshold can be obtained, for example, by taking into account the distance decay characteristics of the two different microphones, the distance from the sound sources of these microphones, etc. (error, for example, can also be taken into account), and the specific threshold can be suitably determined in the design of the device.
With the voice input device, the filtering can be performed on the first signal. With this configuration, the signal from the first microphone having greater distance decay characteristics (i.e., better performance of suppressing remote noise than the second microphone) is utilized as the signal that indicates input sound that is inputted to the voice input device. This configuration is favorable for close-talking voice input devices.
With the voice input device, the first microphone can include a differential microphone, and the second microphone can include a non-directional microphone. With this configuration, the difference in sensitivity to background noise generated at a distance is increased, which makes it easier to suppress noise.
With the voice input device, the first microphone is configured to convert input sound into an electrical signal by vibrating a diaphragm based on the difference between sound pressure applied to one side of the diaphragm and sound pressure applied to the other side. With this configuration, less space is needed for the first microphone. Thus, the voice input device can easily be made more compact.
With the voice input device, the first microphone and the second microphone can be disposed in a single package. With this configuration, the voice input device can easily be made more compact.
With the voice input device, the first microphone and the second microphone can be disposed on a single substrate component.
With the voice input device, the first microphone and the second microphone can be arranged relative to first and second sound channels at least partially defined by the substrate component. The first microphone has a diaphragm that communicates with the first and second sound channels on both sides of the diaphragm of the first microphone. The second microphone has a diaphragm that only communicates with the first sound channel on one side of the diaphragm of the second microphone.
In the illustrated embodiment, the noise suppression method is executed by a voice input device. The noise suppression method includes identifying frequencies of noise by comparing a first signal obtained from a first microphone with a second signal obtained from a second microphone. The second microphone has a lower distance decay rate than the first microphone. The noise suppression method further includes performing filtering to suppress signal strength of the frequencies of the noise that has been identified.
With this configuration, the frequencies of the noise are identified by comparing signals obtained from two types of microphone with different distance decay rates. The noise is suppressed by suppressing the signal strength of frequencies identified as including noise. Therefore, less data needs to be readied in advance in order to suppress noise, and noise suppression can be carried out more accurately.
The present invention provides a voice input device and a noise suppression method with which background noise generated at a distance can be accurately suppressed.
In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts unless otherwise stated.
Also it will be understood that although the terms “first” and “second” may be used herein to describe various components these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, for example, a first component discussed above could be termed a second component and vice-a-versa without departing from the teachings of the present invention. The term “attached” or “attaching”, as used herein, encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to the intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e. one element is essentially part of the other element. This definition also applies to words of similar meaning, for example, “joined”, “connected”, “coupled”, “mounted”, “bonded”, “fixed” and their derivatives. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean an amount of deviation of the modified term such that the end result is not significantly changed.
While only a selected embodiment has been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, unless specifically stated otherwise, the size, shape, location or orientation of the various components can be changed as needed and/or desired so long as the changes do not substantially affect their intended function. Unless specifically stated otherwise, components that are shown directly connected or contacting each other can have intermediate structures disposed between them so long as the changes do not substantially affect their intended function. The functions of one element can be performed by two, and vice versa unless specifically stated otherwise. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiment according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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2013-025244 | Feb 2013 | JP | national |