Abstract:
An information processing apparatus and method provide logic for processing information. In one implementation, an information processing apparatus may include a receiving unit configured to receive an audio signal associated with a motion of a human mandible over a time period. The information processing apparatus may also include a determination unit configured to determine whether the motion of the human mandible corresponds to mastication, based on at least a power of the received audio signal during the time period.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from Japanese Patent Application JP 2011-061694, filed on Mar. 18, 2011, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND 
       [0002]    The disclosed exemplary embodiments relate to a mastication detection device and a mastication detection method. In particular, the disclosed exemplary embodiments relate to devices and methods that identify mastication based on a detection of mastication sounds. 
         [0003]    The importance of the act of chewing when taking a meal, that is mastication, is being reconsidered due to an increase in health consciousness in recent years. Exemplary advantages obtained by sufficiently masticating are outlined below: 
         [0004]    (1) Aids digestion and reduces the burden on the intestines. 
         [0005]    (2) Secretion of saliva is promoted and there is prevention of tooth decay. 
         [0006]    (3) The jaw is developed and teeth alignment and posture are improved. 
         [0007]    (4) It is possible to obtain a sense of fullness due to stimulation of the satiety center, and obesity is suppressed. 
         [0008]    Modern food is often soft and there is a tendency for the number of mastications to fall. Accordingly, it is necessary that mastication is performed with awareness in order to obtain a sufficient number of mastications, but realization of this is difficult. Therefore, up to now, a system is proposed where the number of mastications is automatically detected and indicated to the user. For example, a mastication detection device is proposed where a mastication action is detected by attaching a sensor which detects the movement above the temporomandibular joint. However, in a case where a unique sensor such as this is used, there is a problem in that costs increase. 
         [0009]    For example, in Japanese Unexamined Patent Application Publication No. 11-123185, a technique is disclosed where a mastication action is detected without a unique sensor by using a cheap and easily obtained microphone. That is, the technique uses an earphone which is also a microphone, detects the sound of a change in shape in the vicinity of an entrance to an ear hole which is generated by mastication by inserting an earphone into an ear, and determines mastication using the detected sound. 
       SUMMARY 
       [0010]    In Japanese Unexamined Patent Application Publication No. 11-123185, for example, the detection of mastication is performed by comparing the detected sound and a sample sound recorded beforehand. In this case, an error may occur due to the sound sampled beforehand or due to the food which is eaten and the detection of mastication with high accuracy is difficult. 
         [0011]    It is desirable to detect mastication with high accuracy at a low cost. 
         [0012]    Consistent with an exemplary embodiment, an information processing apparatus includes a receiving unit configured to receive an audio signal associated with a motion of a human mandible over a time period. A determination unit is configured to whether the motion of the human mandible corresponds to mastication, based on at least a power of the received audio signal during the time period. 
         [0013]    Consistent with a further exemplary embodiment, a computer-implemented method receives an audio signal associated with a motion of a human mandible over a time period. The method includes determining, using a processor, whether the motion of the human mandible corresponds to mastication, based on at least a power of the received audio signal during the time period. 
         [0014]    Consistent with another exemplary embodiment, a tangible, non-transitory computer-readable medium stores instructions that, when executed by at least one processor, cause the processor to perform a method that includes receiving an audio signal associated with a motion of a human mandible over a time period. The method includes determining whether the motion of the human mandible corresponds to mastication, based on at least a power of the received audio signal during the time period. 
         [0015]    According to exemplary embodiments of the present disclosure, it is possible to detect mastication with high accuracy at a low cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a block diagram illustrating a configuration example of a mastication detection device according to a first exemplary embodiment of the present disclosure; 
           [0017]      FIGS. 2A to 2C  are diagrams for describing a process of a mastication sound form calculation section which configures the mastication detection device, in accordance with the first exemplary embodiment; 
           [0018]      FIG. 3  is a flowchart illustrating an example of a process sequence of a process for calculating a frame power which is performed by a frame power calculation section of the mastication sound form calculation section, in accordance with the first exemplary embodiment; 
           [0019]      FIGS. 4A and 4B  are diagrams for describing a process for correcting a power threshold in a power threshold calculation section which configures the mastication detection device, in accordance with the first exemplary embodiment; 
           [0020]      FIG. 5  is a flowchart illustrating an example of a process sequence of a process for correcting a power threshold which is performed by the power threshold calculation section, in accordance with the first exemplary embodiment; 
           [0021]      FIG. 6  is a diagram for describing a process for determining mastication in a mastication determination section which configures the mastication detection device, in accordance with the first exemplary embodiment; 
           [0022]      FIG. 7  is a flowchart illustrating an example of a process sequence of a process for determining mastication which is performed by the mastication determination section, in accordance with the first exemplary embodiment; 
           [0023]      FIG. 8  is a block diagram illustrating a configuration example of a system which uses a mastication determination result (detection pulse) of the mastication detection device, in accordance with the first exemplary embodiment; 
           [0024]      FIG. 9  is a diagram illustrating an example of a detection pulse which is the mastication determination result output from the mastication determination section of the mastication detection device, in accordance with the first exemplary embodiment; 
           [0025]      FIG. 10  is a block diagram illustrating a configuration example of a mastication detection device according to a second exemplary embodiment of the present disclosure; 
           [0026]      FIG. 11  is a flowchart illustrating an example of a process sequence of a process for suppressing ambient noise which is performed by an ambient noise suppression section, in accordance with the second exemplary embodiment; and 
           [0027]      FIG. 12  is a diagram of an exemplary computer system, consistent with disclosed exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Below, exemplary embodiments of the present disclosure will be described. Here, the description will be performed in the order below. 
         [0029]    1. First Exemplary Embodiment 
         [0030]    2. Second Exemplary Embodiment 
         [0031]    3. Modified Example 
         [0032]    4. Exemplary Computer Systems 
       1. First Embodiment 
     a. Configuration of Mastication Detection Device 
       [0033]      FIG. 1  illustrates a configuration example of a mastication detection device  100  according to a first exemplary embodiment. The mastication detection device  100  has a mastication sound measurement section  110 , a band pass filter  120 , a mastication sound form calculation section  130 , a power threshold holding section  140 , a power threshold calculation section  150 , a time threshold holding section  160 , and a mastication determination section  170 . 
         [0034]    The mastication sound measurement section  110  measures mastication sound. The mastication sound measurement section  110  is configured by, for example, a microphone, an earphone-type microphone, or the like, and is disposed in an ear of a user or a place which is able to measure mastication sound at a sufficient volume. An output signal of the mastication sound measurement section  110  is, for example, a digital signal with a sampling frequency of approximately 8 kHz. 
         [0035]    The band pass filter  120  is a filter for suppressing a component out of the output signal of the mastication sound measurement section  110  which is surplus and is not a mastication sound component and is a filter which only allows a frequency band which includes many mastication sound components to pass. The band pass filter  120  allows, for example, a frequency band of 50 Hz to 200 Hz where there is a sound component generated due to movement of the temporomandibular joint or a frequency band of 900 Hz to 2000 Hz where there is a sound component of teeth hitting against each other, to pass. 
         [0036]    The mastication sound form calculation section  130  determines a form Pas of a power transition in the time direction of the output signal of the mastication sound measurement section  110  where surplus signal is suppressed by the band pass filter  120 . The mastication sound form calculation section  130  is configured from a frame partition section  131  and a frame power calculation section  132 . The frame partition section  131  divides the output signal of the mastication sound measurement section  110  into frames of a predetermined length. 
         [0037]    For example,  FIG. 2A  illustrates an example of the output signal of the mastication sound measurement section  110  over a time period, as a function of time and amplitude. In  FIG. 2A , an example is shown where background noise is included.  FIG. 2B  illustrates an example of a state where the output signal of the mastication sound measurement section  110  over the time period is divided into frames having, for example, an equal frame length. Here, in the example shown in  FIG. 2B , an example is shown where there is no overlap between frame sections, but there may be overlapping. 
         [0038]    The frame power calculation section  132  determines frame power by calculating an average of the square of each of the sample signals in the time period for each frame. Due to this, the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  is determined.  FIG. 2C  illustrates the form Pas of the power transition in the time direction which is determined to correspond to the output signal of the mastication sound measurement section  110  in  FIG. 2A . 
         [0039]    The flowchart of  FIG. 3  illustrates an example of a process sequence of a process for calculating the frame power, which is performed by the frame power calculation section  132 , in accordance with a disclosed embodiment. The frame power calculation section  132  starts the process in step ST 1 , and moves to the process of step ST 2  after that. In step ST 2 , the frame power calculation section  132  stores signals of a target frame in a buffer with a frame size. 
         [0040]    Next, in step ST 3 , the frame power calculation section  132  determines whether or not all of the sample signals of the target frame have accumulated in the buffer. When all of the signals have not accumulated, the frame power calculation section  132  returns to the process of step ST 2 . On the other hand, when all of the signals have accumulated, the frame power calculation section  132  moves to the process of step ST 4 . 
         [0041]    In step ST 4 , the frame power calculation section  132  squares all of the sample signals in the buffer. Then, in step ST 5 , the frame power calculation section  132  determines the average of the signals which have been squared and the average is the frame power of the target frame. After the process of step ST 5 , the frame power calculation section  132  returns to the process of step ST 2  and repeats the same process described above with the target frame as the next frame. 
         [0042]    Returning to  FIG. 1 , the power threshold holding section  140  holds a power threshold Pth set in advance which is a parameter which is used by the mastication determination section  170 . The power threshold Pth is used in the mastication determination section  170  in order to determine a mastication portion from the form which is determined by the mastication sound form calculation section  130 . The power threshold Pth is determined so as to be able to effectively perform determination of the mastication portion by referencing the form which corresponds to the output signal of the mastication sound measurement section  110  of a plurality of people. 
         [0043]    The power threshold calculation section  150  estimates a background noise level Lbn and corrects the power threshold Pth which is held in the power threshold holding section  140  based on the background noise level Lbn. The power threshold calculation section  150  is configured from a background noise level estimation section  151  and a power threshold correction section  152 . The background noise level estimation section  151  has a buffer which accumulates a sample signal for a previous certain period. The length of the buffer is comparatively longer so as to be able to be stably estimated without being influenced by mastication sound and the like. The background noise level estimation section  151  determines a power average over buffer sections by the same process as the frame power calculation section  132  of the mastication sound form calculation section  130  described above and the power average is set as the background sound level Lbn. 
         [0044]    The power threshold correction section  152  corrects the power threshold Pth which is held by the power threshold holding section  140  using the background sound level Lbn estimated by the background noise level estimation section  151  and a corrected power threshold Pth′ is determined. Specifically, the power threshold correction section  152  acquires the corrected power threshold Pth′ by adding the background sound level Lbn to the power threshold Pth. 
         [0045]      FIG. 4A  illustrates an example of a level relationship between the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  and the power thresholds Pth and Pth′ in a case where there is no background noise, consistent with disclosed embodiments. In this case, the background sound level Lbn is zero and Pth and Pth′ are equal since there is no background noise.  FIG. 4B  illustrates an example of a level relationship between the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  and the power thresholds Pth and Pth′ in a case where there is background noise. In this case, the background sound level Lbn is not zero and Pth′=Pth+Lbn since there is background noise. Due to this, the relationship between the power threshold Pth′ and the form Pas is the same as the case where there is no background noise even in the case where there is background noise. 
         [0046]    The flowchart of  FIG. 5  illustrates an example of a process sequence of a process for correcting the power threshold Pth which is performed by the power threshold calculation section  150 , in accordance with a disclosed embodiment. The power threshold calculation section  150  starts the process in step ST 11 , and moves to the process of step ST 12  after that. In step ST 12 , the power threshold calculation section  150  stores the sample signal in the background noise estimation buffer. In this case, for example, the old sample signals are discarded for each new sample signal which is input. 
         [0047]    Next, in step ST 13 , the power threshold calculation section  150  squares all of the sample signals in the buffer. Then, in step ST 14 , the power threshold calculation section  150  determines the average of the sample signals which have been squared and the average is the background sound level Lbn. Next, in step ST 15 , the power threshold calculation section  150  reads out the power threshold Pth from the power threshold holding section  140 . Then, in step ST 16 , the power threshold calculation section  150  acquires the corrected power threshold Pth′ by adding the background sound level Lbn to the power threshold Pth. After the process of step ST 16 , the power threshold calculation section  150  returns to step ST 12  and repeats the same process described above. 
         [0048]    Here, in the description above, it has been described that the correction of the power threshold Pth is performed by estimating the background noise level Lbn in the power threshold calculation section  150  even at a time when the mastication sound is measured by the mastication sound measurement section  110 . However, the power threshold calculation section  150  may acquire the power threshold Pth′ by performing a correction process described above at a time when the mastication sound is not being measured by the mastication sound measurement section  110 . Due to this, it is possible to perform the estimation of the background noise level Lbn without being influenced by the mastication sound and it is possible to increase the accuracy of the process for correcting the power threshold Pth. In this case, the using of the mastication determination result of the mastication determination section  170  in the operational control of the power threshold calculation section  150  is considered. 
         [0049]    Returning to  FIG. 1 , the time threshold holding section  160  holds a time threshold set in advance which is a parameter used by the mastication determination section  170 . The time threshold holding section  160  holds an upper limit time threshold Tthh and a lower limit time threshold Tthl where a power larger than the power threshold Pth′ described above is held as a time threshold so as to determine the mastication portion in the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110 . 
         [0050]    The mastication determination section  170  determines mastication based on the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  which is determined by the mastication sound form calculation section  130  and outputs the mastication determination result. In this case, the mastication determination section  170  determines the mastication portion based on the form Pas by applying the power threshold Pth′ obtained by the power threshold calculation section  150  and the upper limit time threshold Tthh and the lower limit time threshold Tthl held by the time threshold holding section  160  with regard to the form Pas. Then, the mastication determination section  170  outputs, for example, a detection pulse at a timing when the mastication portion is determined. 
         [0051]    In this case, as shown in  FIG. 6 , the mastication determination section  170  determines a portion in the form Pas where a power which is larger than the power threshold Pth′ is held for a period between the lower limit time threshold Tthl and the upper limit time threshold Tthh as the mastication portion. 
         [0052]    The flowchart of  FIG. 7  illustrates an example of a process sequence of a process for determining mastication, which is performed by the mastication determination section  170 , in accordance with a disclosed embodiment. The mastication determination section  170  starts the process in step ST 21 , and moves to the process of step ST 22  after that. In step ST 22 , the mastication determination section  170  reads out a mastication sound form signal obtained from the mastication sound form calculation section  130 , that is, a frame power signal which configures the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110 . 
         [0053]    Next, in step ST 23 , the mastication determination section  170  determines whether or not the mastication sound form signal (frame power signal) read-out in step ST 22  is larger than the power threshold Pth′. When the mastication sound form signal is not larger than the power threshold Pth′, the mastication determination section  170  returns to step ST 22 , reads out the next mastication sound form signal, and repeats the same process as described above. On the other hand, when the mastication sound form signal is larger than the power threshold Pth′, the mastication determination section  170  moves to the process of step ST 24 . 
         [0054]    In step ST 24 , the mastication determination section  170  reads out the next mastication sound form signal. Then, in step ST 25 , the mastication determination section  170  counts the number of read-out mastication sound form signals. That is, the mastication determination section  170  increase the count value by one for each reading out of the mastication sound form signal in step ST 24 . The count value indicates a power holding period where a state, where the mastication sound form signal (frame power signal) is larger than the power threshold Pth′, is held. 
         [0055]    Next, in step ST 26 , the mastication determination section  170  determines whether or not the mastication sound form signal read-out in step ST 24  is larger than the power threshold Pth′. When the mastication sound form signal is larger than the power threshold Pth′, the mastication determination section  170  returns to step ST 24 , reads out the next mastication sound form signal, and repeats the same process as described above. On the other hand, when the mastication sound form signal is not larger than the power threshold Pth′, the mastication determination section  170  moves to the process of step ST 27 . 
         [0056]    In step ST 27 , the mastication determination section  170  determines whether the power holding period is accommodated between an upper limit (the upper limit time threshold Tthh) and a lower limit (the lower limit time threshold Tthl) of the time threshold. When the power holding period is not accommodated between the limits, in step ST 29 , the mastication determination section  170  resets the power holding period, that is, the count value, and after that, returns to the process of step ST 22  and repeats the same process described above. On the other hand, when the power holding period is accommodated between the limits, the mastication determination section  170  determines that the power holding period is the mastication portion and outputs the detection pulse in step ST 28 . After the process of step ST 28 , in step ST 29 , the mastication determination section  170  resets the power holding period, that is, the count value, and after that, returns to the process of step ST 22  and repeats the same process described above. 
         [0057]    The operation of the mastication detection device  100  shown in  FIG. 1  will be described. The mastication sound is measured in the mastication sound measurement section  110 . The output signal of the mastication sound measurement section  110  is supplied to the mastication sound form calculation section  130  and the power threshold calculation section  150  via the band pass filter  120 . In the band pass filter  120 , a component out of the output signal of the mastication sound measurement section  110 , which is surplus and is not a mastication sound component, is suppressed. 
         [0058]    In the mastication sound form calculation section  130 , the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110 , where the surplus signal has been suppressed by the band pass filter  120 , is determined. That is, using the frame partition section  131 , the output signal of the mastication sound measurement section  110  is sectioned for each predetermined length of frame length. Then, using the frame power calculation section  132 , the frame power is determined by calculating the average of the square of each of the sample signals in the frame for each frame, and due to this, the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  is determined. 
         [0059]    In addition, in the power threshold calculation section  150 , the power threshold Pth which is held in the power threshold holding section  140  is corrected based on the background noise level Lbn. That is, in the background noise level estimation section  151 , a power average over buffer sections with a predetermined length is determined and the power average is set as the background sound level Lbn. Then, in the power threshold correction section  152 , the background sound level Lbn estimated by the background noise level estimation section  151  is added to the power threshold Pth which is held by the power threshold holding section  140  and the corrected power threshold Pth′ is determined. 
         [0060]    The form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110 , which is acquired by the mastication sound form calculation section  130 , is supplied to the mastication determination section  170 . In addition, the power threshold Pth′ after the correction calculated in the power threshold calculation section  150  and the upper limit time threshold Tthh and the lower limit time threshold Tthl held in the time threshold holding section  160  are supplied to the mastication determination section  170 . 
         [0061]    In the mastication determination section  170 , mastication is determined based on the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  and the mastication determination result is output. In this case, in the mastication determination section  170 , the power threshold Pth′ and the upper limit time threshold Tthh and the lower limit time threshold Tthl are applied with regard to the form Pas. Then, a portion in the form Pas where a power which is larger than the power threshold Pth′ is held for a period between the lower limit time threshold Tthl and the upper limit time threshold Tthh is determined as the mastication portion, and for example, the detection pulse is output. 
         [0062]    As described above, in the mastication detection device  100  shown in  FIG. 1 , the form Pas of the power transition in the time direction of the output signal of the mastication sound measurement section  110  is determined using the mastication sound form calculation section  130 . Then, in the mastication determination section  170 , mastication is determined by the power threshold Pth′ and the time thresholds Tthh and Tthl being applied to the form Pas. As a result, it is possible to detect mastication with high accuracy at a low cost. 
         [0063]    In addition, in the mastication detection device  100  shown in  FIG. 1 , the background noise level Lbn is estimated by the power threshold calculation section  150 . Then, the power threshold Pth which is held in the power threshold holding section  140  is corrected according to the background noise level Lbn and the power threshold Pth′ which is actually used is acquired by the mastication determination section  170 . As a result, it is possible to avoid erroneous detection of mastication due to background noise included in the output signal of the mastication sound measurement section  110 . 
         [0064]    In addition, in the mastication detection device  100  shown in  FIG. 1 , the band pass filter  120  which sets a frequency band which includes many mastication sound components as a pass band is disposed in the output side of the mastication sound measurement section  110 . Then, the surplus component included in the output signal of the mastication sound measurement section  110  is suppressed by the band pass filter  120 . As a result, it is possible to avoid erroneous detection of mastication due to a surplus component included in the output signal of the mastication sound measurement section  110 . 
         [0065]    Here, it is possible that the mastication determination result of the mastication detection device  100  shown in  FIG. 1  is used in automatic measuring of the number of mastications, a health management system, or the like.  FIG. 8  illustrates an example of a configuration of a system, which uses the mastication determination result (detection pulse) of the mastication detection device  100 , in accordance with a disclosed embodiment. In  FIG. 8 , the parts which correspond to  FIG. 1  are given the same reference numerals and detail description thereof is omitted. 
         [0066]    Other than the mastication detection device  100 , the system is provided with a counter  210 , a mastication start and end determination section  220 , and a reporting section  230 . The counter  210  counts the detection pulses which are the mastication determination result output from the mastication detection device  100 . The mastication start and end determination section  220  determine the start of mastication and the end of mastication based on the detection pulses which are the mastication determination results output from the mastication detection device  100 . 
         [0067]      FIG. 9  illustrates an example of a detection pulse which is the mastication determination result output from the mastication determination section  170 , in accordance with a disclosed embodiment. From the mastication determination section  170 , the output of the detection pulse starts after a mastication period begins, the detection pulse is continuously output after that, and the output of the detection pulse is stopped after the mastication period ends. As a result, the mastication start and end determination section  220  monitors the detection pulse which is output from the mastication determination section  170  and determines that mastication has started when the output of the detection pulse has started. In addition, the mastication start and end determination section  220  monitors the detection pulse which is output from the mastication determination section  170  after the mastication has started and determines that mastication has ended when the output of the detection pulse has stopped. 
         [0068]    The counter  210  resets the count value, for example, at a timing when the mastication starts or the mastication ends based on a determination result of the mastication start and end determination section  220 . Due to this, the count value of counter  210  in the mastication period shows the number of mastications from the start of mastication. Here, the resetting of the count value of the counter  210  may be configured, for example, so as to be operated by the user at the start of mastication. 
         [0069]    The reporting section  230  is provided with a display device such as a liquid crystal panel and a sound producing device such as a speaker or a buzzer, and when the count value of the counter  210  becomes a predetermined value which is set in advance or set by a user, this is reported to the user using the display, sound, or both. Here, the reporting section  230  may be configured so as to report the changes in the count value of the counter  210  at that time to the user using the display, sound, or both. 
       2. Second Embodiment 
     a. Configuration of Mastication Detection Device 
       [0070]      FIG. 10  illustrates a configuration example of a mastication detection device  100 A according to a second exemplary embodiment of the present disclosure. The mastication detection device  100 A is configured so that an ambient noise measurement section  180  and an ambient noise suppression section  190  are further added to the mastication detection device  100  which is shown in  FIG. 1  described above. In  FIG. 10 , the parts which correspond to  FIG. 1  are given the same reference numerals and detail description thereof is omitted. The ambient noise measurement section  180  is disposed in a position which is separate from the mastication sound measurement section  110  and it is necessary to be careful that the mastication sound does not enter the ambient noise measurement section  180 . 
         [0071]    The ambient noise suppression section  190  suppresses an ambient noise component which is included in the output signal of the mastication sound measurement section  110  with a high degree of accuracy using the output signal of the ambient noise measurement section  180 . In the surroundings where the user takes a meal, there are many ambient noises such as from an air conditioner or the like. The suppressing of the ambient noise in this manner is performed because the ambient noise has a negative effect on the mastication detection. 
         [0072]    The ambient noise suppression section  190  is configured from an adaptive filter section  191  and a noise subtraction section  192 . The adaptive filter section  191  estimates a transfer function from a measurement point in the ambient noise measurement section  180  (ambient noise measurement point) to a measurement point in the mastication sound measurement section  110  (mastication sound measurement point). Here, the mastication sound measurement point has a meaning of a set point in the mastication sound measurement section  110  and the ambient noise measurement point has a meaning of a set point in the ambient noise measurement section  180 . The adaptive filter section  191  is typically configured by, for example, a FIR filter or the like. By filtering the output signal of the ambient noise measurement section  180  using the adaptive filter section  191 , the ambient noise component at the mastication sound measurement point is estimated with a high degree of accuracy. 
         [0073]    In addition, in the adaptive filter section  191 , the output signal of the noise subtraction section  192  which will be described later is fed back and a filter coefficient of the adaptive filter section  191  is appropriately changed. A detailed description is omitted but as an adaptive algorithm, there is, for example, a LMS (Least Mean Squares) method, a RLS (Recursive Least Squares) method, and the like. 
         [0074]    The noise subtraction section  192  suppresses the ambient noise component included in the output signal of the mastication sound measurement section  110  by performing a subtraction process with the ambient noise component at the mastication sound measurement point which is estimated using the adaptive filter section  191  and the output signal of the ambient noise measurement section  110 . The mastication detection device  100 A uses a signal after the ambient noise component has been suppressed using the ambient noise suppression section  190  as described above and not by using the output signal of the mastication sound measurement section  110  as it is. 
         [0075]    The flowchart of  FIG. 11  illustrates an example of a process sequence of a process for suppressing ambient noise which is performed by the ambient noise suppression section  190 , in accordance with a disclosed embodiment. The ambient noise suppression section  190  starts the process in step ST 31 , and moves to the process of step ST 32  after that. In step ST 32 , the ambient noise suppression section  190  initializes the coefficient of the adaptive filter section  191 . 
         [0076]    Next, in step ST 33 , the ambient noise suppression section  190  reads out the output signal of the ambient noise measurement section  180 . Then, in step ST 34 , the ambient noise suppression section  190  passes the output signal of the ambient noise measurement section  180  through an adaptive filter. 
         [0077]    Next, in step ST 35 , the ambient noise suppression section  190  reads out the output signal of the mastication sound measurement section  110 . Then, in step ST 36 , the ambient noise suppression section  190  subtracts the output signal of the mastication sound measurement section  110  from the output signal from the adaptive filter and outputs the subtraction result. In step ST 37 , the ambient noise suppression section  190  changes the coefficient of the adaptive filter by referencing the subtraction output, and after that, returns to step ST 33  and repeats the same process as described above. 
         [0078]    Other than this, the mastication detection device  100 A shown in  FIG. 10  is configured in the same manner as the mastication detection device  100  shown in  FIG. 1  described above. 
         [0079]    The operation of the mastication detection device  100 A shown in  FIG. 10  will be described. In the mastication sound measurement section  110 , the mastication sound is measured. The output signal of the mastication sound measurement section  110  is supplied to the noise subtraction section  192  of the ambient noise suppression section  190 . In addition, in the ambient noise measurement section  180 , ambient noise such as from an air conditioner is measured. The output of the ambient noise measurement section  180  is supplied to the adaptive filter section  191  of the ambient noise suppression section  190  and the ambient noise component in the mastication sound measuring point is estimated. The ambient noise component estimated in this manner, that is, the output signal of the adaptive filter section  191  is supplied to the noise subtraction section  192 . 
         [0080]    In the noise subtraction section  192 , the subtraction process is performed with the ambient noise component at the mastication sound measurement point which is estimated using the adaptive filter section  191  and the output signal of the ambient noise measurement section  110  and a signal is obtained where the ambient noise component has been suppressed. The output signal of the noise subtraction section  192  is supplied to the mastication sound form calculation section  130  and the power threshold calculation section  150  via the band pass filter  120 . A detail description is omitted but hereinafter is the same as the mastication detection device  100  shown in  FIG. 1 . 
         [0081]    As described above, in the mastication detection device  100 A shown in  FIG. 10 , it is possible to obtain the same effects since the configuration is the same as the mastication detection device  100  shown in  FIG. 1 . In addition, in the mastication detection device  100 A shown in  FIG. 10 , the output signal of the mastication sound measurement section  110  is not used as it is and is used after the ambient noise component has been suppressed with a high degree of accuracy using the ambient noise suppression section  190 . As a result, it is possible to avoid erroneous detection of mastication due to the ambient noise component included in the output signal of the mastication sound measurement section. 
       3. Modified Example 
       [0082]    Here, in the embodiments described above, the band pass filter  120  is inserted in the output side of the mastication sound measurement section  110 , but the band pass filter  120  is not a necessary configuration. In addition, in the embodiments described above, there is a configuration where the power threshold Pth which is held by the power threshold holding section  140  is corrected using the power threshold calculation section  150  and the power threshold Pth′ after correction is used in the mastication detection device  170 . However, in surroundings where there is hardly any background noise, this correction is not necessary. In addition, it is possible to consider the omission of the power threshold calculation section  150  by the power threshold Pth which is held by the power threshold holding section  140  being set in advance so as to take the background noise level in consideration. 
         [0083]    Here, it is possible for the present disclosure to be configured as per below. 
         [0084]    (1) A mastication detection device is provided with a mastication sound measurement section which measures mastication sound, a mastication sound form calculation section which determines a form of power transition in the time direction of an output signal of the mastication sound measurement section, and a mastication determination section which determines mastication based on the form which is determined by the mastication sound form calculation section. 
         [0085]    (2) The mastication detection device of (1) where the mastication determination section determines a portion in the form where a power which is larger than a power threshold is held for a period between a lower limit time threshold and an upper limit time threshold as a mastication portion. 
         [0086]    (3) The mastication detection device of (2) is further provided with a background noise level estimation section which estimates a background noise level based on the output signal of the mastication sound measurement section, and a power threshold correction section which corrects the power threshold based on the background noise level which is estimated by the background noise level estimation section. 
         [0087]    (4) The mastication detection device of (3) where the power threshold correction section obtains the power threshold which is corrected by adding the background noise level which is estimated by the background noise level estimation section to the power threshold which is set in advance. 
         [0088]    (5) Any of the mastication detection devices of (1) to (4) is further provided with a band pass filter which is disposed at an output side of the mastication sound measurement section and sets a frequency band which includes many mastication sound components as a pass band, where the mastication sound form calculation section determines the form of the power transition in the time direction of the output signal of the band pass filter. 
         [0089]    (6) Any of the mastication detection devices of (1) to (5) is further provided with an ambient noise measurement section which measures ambient noise and an ambient noise suppression section which suppresses an ambient noise component included in the output signal of the mastication sound measurement section based on an output signal of the ambient noise measurement section, where the mastication noise form calculation section determines the form of the power transition of the output signal of the mastication sound measurement section after the ambient noise component is suppressed by the ambient noise suppression section. 
         [0090]    (7) The mastication detection device of (6) where the ambient noise suppression section has an adaptive filter which estimates a transfer function from a measurement point in the ambient noise measurement section to a measurement point in the mastication sound measurement section and suppresses the ambient noise component included in the output signal of the mastication sound measurement section by performing a subtraction process with a signal, which is obtained by filtering the output signal of the mastication sound measurement section and the output signal of the ambient noise measurement section using the adaptive filter. 
       4. Exemplary Computer Systems 
       [0091]    In an embodiment, the functions of the above-described mastication detection device, and the various sections and units, associated with the mastication detection device, can be achieved using, for example, a computer system  1200  shown in  FIG. 12 . Further, in an additional embodiment, the function of one or more of the structural elements, sections, and units may be achieved by controlling computer system  1200  using instructions stored on a tangible, non-transitory computer-readable storage medium. In such embodiments, examples of computer system  1200  include, but are not limited to a personal computer, a laptop computer, a tablet computer, a mobile phone, a smart phone, a personal digital assistance (PDA), a mobile information terminal, a mobile game console, and/or a head- or ear-mounted specialized computing device. 
         [0092]    As shown in  FIG. 12 , computer system  1200  includes a central processing unit (CPU)  1202 , a host bus  1208 , a bridge  1210 , and a tangible computer-readable storage media, examples of which include a read only memory (ROM)  1204 , and a random access memory (RAM)  1206 . Furthermore, computer system  1200  includes an external bus  1212 , an interface  1214 , an input unit  1216 , an output unit  1218 , a storage unit  1220 , a drive  1222 , a connection port  1224 , and a communication unit  1226 . 
         [0093]    CPU  1202  may function as an arithmetic processing unit or a control unit, for example, and controls the entire operation or a part of the operation of each structural element based on various instructions stored within ROM  1204 , RAM  1206 , storage unit  1220 , or a removable recording medium  1228 . ROM  1204  may be configured to store, for example, a instructions to be loaded on CPU  1202  or data or the like used in an arithmetic operation. RAM  1206  temporarily or permanently stores, for example, instructions to be loaded on CPU  1202  or various parameters or the like arbitrarily changed in execution of a program. 
         [0094]    These structural elements are connected to each other by, for example, host bus  1208  capable of performing high-speed data transmission. Host bus  1208  is connected through bridge  1210  to external bus  1212  whose data transmission speed is relatively low, for example. Furthermore, input unit  1216  may include, for example, a mouse, a keyboard, a touch panel, a button, a switch, or a lever. Also, input unit  1216  may be a remote control that can transmit a control signal by using an infrared ray or other radio waves. 
         [0095]    Output unit  1218  may be a display device that includes, but is not limited to, a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display panel (PDP), an electro-luminescence display (ELD), and audio output device (e.g., a speaker or headphones), a printer, a mobile phone, and/or a facsimile, that may provide a visual or auditory notification to a user of acquired information. 
         [0096]    Storage unit  1220  is an example of a tangible, non-transitory computer-readable storage medium or device for storing various data. Storage unit  1220  may include, for example, a magnetic storage device such as a hard disk drive (HDD), a semiconductor storage device, an optical storage device, a magneto-optical storage device. 
         [0097]    Drive  1222  is a device that reads information recorded on removable recording medium  1228  such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory, or writes information in removable recording medium  1228 . Removal recording medium  1228  is another example of a tangible, non-transitory storage medium. 
         [0098]    Connection port  1224  may be a port that includes, but is not limited to, a USB port, an IEEE13124 port, a SCSI, an RS-232C port, or a port for connecting an externally connected device  1230 , such as an optical audio terminal. Externally connected device  1230  may be, for example, a printer, a mobile music player, a digital camera, a digital video camera, or an IC recorder. 
         [0099]    Communication unit  1226  is a communication device to be connected to a network  1232 , and is, for example, a communication card for a wired or wireless LAN, Bluetooth, or wireless USB, an optical communication router, an ADSL router, or a modem for various types of communication. Network  1232  connected to communication unit  1226  is configured from a wire-connected or wirelessly connected network, and is the Internet, a home-use LAN, infrared communication, visible light communication, broadcasting, or satellite communication, for example. 
         [0100]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.