JP2013084106A - Detection device and detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection device capable of detecting a desired sound with high accuracy.SOLUTION: A detection device includes: a sensor for detecting a sound; a zero-cross point detector 102 for detecting a zero-cross point at which an amplitude of an acoustic signal waveform of the sound detected by the sensor becomes zero; a waveform area calculation section 103 for calculating a waveform area that is a summation of absolute values of amplitudes of acoustic signal waveforms between zero-cross points; and an abnormality determination section 104 that compares the waveform area calculated by the waveform area calculation section 103 with a preset threshold and determines that an abnormality occurs when the waveform area is larger than the threshold.

Description

  The present invention relates to a detection device and a detection method.

  Conventionally, a sensor that detects the impact sound of a person walking is installed in the site of a building to be guarded, and when the sensor in the site reacts to an object, it is determined that there is an illegal intruder who attempts to enter the building. Security systems that output alarms to eliminate illegal intruders, such as operating devices such as threatening bells and emergency lights, are known.

  As a technique for detecting sound, for example, Patent Document 1 discloses a vehicle inspection device that inspects sound / vibration generated in a vehicle. This vehicle inspection device creates a waveform diagram with the horizontal axis representing the speed of travel of the vehicle and the vertical axis representing sound, and the area of the range in which sound exceeding the preset threshold of the sound pressure level was observed And the degree of sound / vibration is evaluated by comparing the accumulated area value with the allowable area value.

JP 2009-216604 A

  However, in areas to be guarded by the security system, sounds other than human walking, such as rain and footsteps of small animals other than humans, are also generated. For this reason, provision of the technique which detects only a footstep sound of an illegal intruder correctly from the sound detected by the sensor is desired.

  The present invention has been made in view of the above, and an object of the present invention is to provide a detection device and a detection method capable of detecting a desired sound such as a human walk with high accuracy.

  In order to solve the above-described problems and achieve the object, the present invention is a detection device, a sensor for detecting sound, and a zero cross point at which the amplitude of the acoustic signal waveform of the sound detected by the sensor becomes zero A waveform area calculation unit that calculates a waveform area that is a sum of absolute values of amplitudes of the acoustic signal waveform between the zero cross points, and the waveform area calculated by the waveform area calculation unit And an abnormality determining unit that determines that an abnormality has occurred when the waveform area is larger than the threshold.

  Further, the present invention is a detection method for detecting an abnormality in a detection device, wherein a sensor detects a sound, and a zero-cross point detection unit detects an amplitude of an acoustic signal waveform of the sound detected in the detection step. A zero-cross point detecting step for detecting a zero-cross point where the zero is zero, and a waveform area calculating step for calculating a waveform area, which is a sum of absolute values of amplitudes of the acoustic signal waveform between the zero-cross points, An abnormality determination step in which an abnormality determination unit compares the waveform area calculated in the waveform area calculation step with a preset threshold value and determines that an abnormality has occurred when the waveform area is larger than the threshold value. It is characterized by including.

  According to the present invention, there is an effect that a desired sound can be detected with high accuracy.

FIG. 1 is an overall configuration diagram of an intrusion detection system according to the present embodiment. FIG. 2 is a schematic diagram showing a construction example of the tube of the acoustic tube sensor. FIG. 3 is a schematic diagram showing a state in which an acoustic tube sensor is embedded in soil, gravel, or the like. FIG. 4 is a block diagram illustrating a functional configuration of the intrusion detection device. FIG. 5 is a graph showing a time change of the amplitude of the acoustic signal waveform. FIG. 6 is a diagram for explaining the processing of the waveform area calculation unit. FIG. 7 is a flowchart showing security processing in the intrusion detection system. FIG. 8 is a diagram illustrating an acoustic signal waveform obtained with respect to walking of a person and an acoustic signal waveform obtained with respect to throwing a ball into a guard area that is a false detection factor. FIG. 9 is an enlarged view of an acoustic signal waveform obtained for a person walking. FIG. 10 is an enlarged view of the acoustic signal waveform obtained for the throwing of the ball. FIG. 11 is a diagram showing the waveform areas calculated from the acoustic signals of the human walking and the ball throwing shown in FIG. FIG. 12 is a diagram illustrating the acoustic signal after the high frequency component is removed by the low-pass filter. FIG. 13 is a diagram illustrating a modification of the acoustic tube sensor. FIG. 14 is a diagram illustrating a modification of the acoustic tube sensor.

  Embodiments of a detection device and a detection method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of an intrusion detection system according to the present embodiment. As shown in FIG. 1, the intrusion detection system according to the present embodiment includes an acoustic tube sensor 400 installed in a monitoring area, and an intrusion detection device 100 connected to the acoustic tube sensor 400.

  As shown in FIG. 1, the acoustic tube sensor 400 has a tube 300 as a hollow tube having elasticity, and a microphone 200 as a sound collection unit provided so as to seal an opening at one end of the tube 300. doing. In the acoustic tube sensor 400, when an impact is applied such as when the tube 300 is stepped on, the sound of the impact propagates through the hollow tube, and the sound is collected by the microphone 200, and the collected acoustic signal is collected. Is sent to the intrusion detection device 100.

  The intrusion detection device 100 performs an abnormality determination that an intruder has entered the monitoring area based on the acoustic signal transmitted from the microphone 200 of the acoustic tube sensor 400.

  The acoustic tube sensor 400 is installed at the location of the monitoring area to be monitored. The acoustic tube sensor 400 can be embedded in soil or gravel. FIG. 2 is a schematic diagram illustrating an example in which the tube 300 of the acoustic tube sensor 400 is embedded in soil, gravel, mat, or the like on the outer periphery of a detached house. FIG. 3 is a schematic diagram showing a state in which the acoustic tube sensor 400 is embedded in soil, gravel, or the like.

  If the acoustic tube sensor 400 is embedded in a substance that transmits sound to the acoustic tube sensor 400, the acoustic tube sensor 400 can be installed at any location.

  Next, details of the intrusion detection device 100 will be described. FIG. 4 is a block diagram showing a functional configuration of the intrusion detection apparatus 100 according to the present embodiment. As shown in FIG. 4, the intrusion detection apparatus 100 according to the present embodiment includes an AD conversion unit 101, a zero-cross point detection unit 102, a waveform area calculation unit 103, an abnormality determination unit 104, an alarm output unit 105, And a storage unit 110.

  The AD conversion unit 101 performs A / D conversion on the analog signal collected and propagated by the microphone 200 of the acoustic tube sensor 400 into a digital acoustic signal (hereinafter referred to as “acoustic signal”). In the present embodiment, the sampling frequency of the acoustic signal is 8 KHz.

  The zero cross point detection unit 102 specifies a zero cross point from the A / D converted acoustic signal. Here, the zero cross point is a point where the amplitude of the acoustic signal waveform intersects the time axis, that is, a point where the amplitude of the acoustic signal waveform becomes zero. FIG. 5 is a diagram for explaining the zero-cross point. FIG. 5 is a graph showing temporal changes in the amplitude of the acoustic signal waveform. The horizontal axis of the graph indicates time, and the vertical axis indicates amplitude. In the graph shown in FIG. 5, the intersection of the amplitude of the acoustic signal waveform and the time axis is the zero cross point.

ここで、ｘ（ｔ）は、時刻ｔにおける信号波形の振幅値すなわちサンプル値である。ｚｃは、ゼロクロス判定値である。ゼロクロス点検出部１０２は、ゼロクロス判定値（ｚｃ）が０以下である場合に、ゼロクロス点であると判断する。 Specifically, the zero-cross point detection unit 102 determines whether or not it is a zero-cross point according to (Equation 1).

Here, x (t) is an amplitude value of the signal waveform at time t, that is, a sample value. zc is a zero cross determination value. The zero-cross point detection unit 102 determines that the zero-cross point is a zero-cross point when the zero-cross determination value (zc) is 0 or less.

  The storage unit 110 stores various information. The storage unit 120 stores a waveform area calculated by a waveform area calculation unit 103 described later, an abnormality detection threshold used by the abnormality determination unit 104, and the like.

ここで、ｈａｌｆＡｒｅａ（ｔ）は、時刻ｔにおける半周期分の波形面積であり、ｈａｌｆＡｒｅａ（ｔ−１）は、時刻ｔの直前までに加算された波形面積の値である。波形面積算出部１０３は、（式２）に示すように、サンプル値が得られる度に、直前までに加算された波形面積値に今回得られたサンプル値（ｘ（ｔ））の絶対値を加算することにより、波形面積（ｈａｌｆＡｒｅａ（ｔ））を得る。 The waveform area calculation unit 103 calculates the waveform area based on the acoustic signal waveform. The intrusion detection apparatus 100 according to the present embodiment performs abnormality detection based on the value of the waveform area for one cycle, and the waveform area calculation unit 103 performs the waveform of the acoustic signal waveform for one cycle. Calculate the area. Here, the waveform area is the sum of absolute values of sample values of the acoustic signal obtained between two adjacent zero cross points.
Specifically, when the zero-cross point is detected, the waveform area calculation unit 103 starts adding the sample values according to (Expression 2), and calculates the waveform area (halfArea (t)) for a half cycle according to (Expression 2). To do.

Here, halfArea (t) is a waveform area corresponding to a half cycle at time t, and halfArea (t−1) is a value of the waveform area added up to immediately before time t. As shown in (Equation 2), the waveform area calculation unit 103 calculates the absolute value of the sample value (x (t)) obtained this time to the waveform area value added immediately before each time the sample value is obtained. The waveform area (halfArea (t)) is obtained by adding.

When the zero cross point is detected, the waveform area calculation unit 103 calculates the waveform area (HalfArea (t) obtained until (t−1) immediately before the time (t) at which the zero cross point is detected by (Equation 3). -1)) is stored in the storage unit 110 as a waveform area (prevHalfArea). Here, the waveform area (prevHalfArea) is a waveform area corresponding to a half cycle of the acoustic signal waveform.

When a zero cross is detected, the waveform area calculation unit 103 further resets the value of the waveform area being added (HalfArea (t)) by (Equation 4).

なお、波形面積算出部１０３は、ゼロクロス点が検出された場合には、半周期分の波形面積と同様に、１周期分の波形面積の値もリセットする。 The waveform area calculation unit 103 calculates the waveform area (halfArea (t)) for the above half cycle when the previous waveform area (prevHalfArea) is stored in the storage unit 110, and (Formula 5) To calculate the waveform area (Area (t)) for one period.

When a zero cross point is detected, the waveform area calculation unit 103 resets the value of the waveform area for one cycle similarly to the waveform area for a half cycle.

  FIG. 6 is a diagram for explaining the processing of the waveform area calculation unit 103. During the second half-cycle acoustic signal detection, the waveform area of the first half-cycle already calculated by the waveform area calculation unit 103 is stored in the storage unit 110 as the previous waveform area (prevHalfArea). The waveform area calculation unit 103 calculates the waveform area (Area (t)) for one cycle while calculating the waveform area (halfArea (t)) of the second half cycle at the time t.

  Returning to FIG. 4, the abnormality determination unit 104 compares the waveform area for one cycle calculated by the waveform area calculation unit 103 with the abnormality detection threshold value stored in the storage unit 110, and the waveform area is determined to be the abnormality detection threshold value. If it is larger than that, it is determined that an abnormal sound has occurred, that is, an abnormal state in which there is a high possibility that an intruder has entered the monitoring area.

  The alarm output unit 105 outputs an alarm when the abnormality determination unit 104 determines that an abnormal state has occurred, or transmits an abnormality notification to a monitoring center (not shown) via the network.

  FIG. 7 is a flowchart showing security processing in the intrusion detection system. In the security process, the intrusion detection system first starts detection of an acoustic signal by the acoustic tube sensor 400 (step S100). Further, the AD conversion unit 101 of the intrusion detection apparatus 100 performs A / D conversion on the acoustic signal (step S101). During the security process, the acoustic tube sensor 400 always continues to detect the acoustic signal, and the AD conversion unit 101 performs the A / D conversion process every time the acoustic signal is detected.

  Subsequently, the zero cross point detection unit 102 calculates a zero cross determination value (zc) based on the calculated sample value of the acoustic signal (step S102), and detects the zero cross point based on the zero cross determination value. When the zero cross determination value (zc) is larger than 0, that is, when it is not the zero cross point (No at Step S103), the waveform area calculation unit 103 calculates the waveform area for a half cycle (Step S104).

  At this time, when the waveform area for the previous half cycle is stored in the storage unit 110 (step S105, Yes), the waveform area calculation unit 103 calculates the waveform area for the half cycle calculated in step S104. Then, the waveform area for one cycle is calculated by adding the waveform areas for the previous half cycle stored in the storage unit 110 (step S106). In step S105, when the waveform area for the previous half cycle is not stored in the storage unit 110 (No in step S105), the process returns to step S100, and the calculation of the area for the half cycle is continued.

  When the waveform area for one cycle is calculated in step S106, the abnormality determination unit 104 next calculates the abnormality detection threshold value stored in the storage unit 110 and the waveform area for one cycle calculated in step S106. Compare values. When the waveform area for one cycle is larger than the abnormality detection threshold (Yes in step S107), the abnormality determination unit 104 determines that an abnormality has occurred, and the alarm output unit 105 performs alarm output, network distribution, or the like. A notification is made that an abnormality has occurred (step S108). Furthermore, when security is continued (step S109, No), the process returns to step S100. When the security is to be ended (step S109, Yes), the abnormality detection process is completed.

  On the other hand, when the zero-cross point detection unit 102 detects the zero-cross point in step S103, that is, when the zero-cross determination value (zc) is 0 or less (step S103, Yes), the waveform area calculation unit 103 continues to the previous step. The calculated waveform area for the half cycle is stored in the storage unit 110 as the previous waveform area. That is, the previous waveform area stored in the storage unit 110 is updated (step S120). When the previous waveform area is not stored in the storage unit 110, the waveform area for the half cycle calculated up to immediately before is newly stored in the storage unit 110 as the previous waveform area.

  Further, the waveform area calculation unit 103 resets the waveform area for the half cycle and the waveform area for one cycle, which have been calculated until immediately before (step S121), and proceeds to step S109.

  Thus, in the intrusion detection system according to the present embodiment, every time a sample value of an acoustic signal is obtained, the waveform area is updated by adding the obtained sample value to the waveform area for one period. Every time the waveform area is updated, the abnormality determination is performed by comparing the updated waveform area for one period with the abnormality detection threshold, so that the occurrence of abnormality can be detected in real time.

  FIG. 8 shows the acoustic signal waveform obtained for the walking of the person to be detected by the intrusion detection system according to the present embodiment, and the throwing of the ball into the security area that is a false detection factor. It is a figure which shows an acoustic signal waveform. The horizontal axis of the graph shown in FIG. 8 indicates the number of samples of the acoustic signal, and the vertical axis indicates the amplitude. 9 and 10 are enlarged views of acoustic signal waveforms obtained for walking and throwing a ball, respectively. In this example, throwing the ball is shown as an example of a false detection factor. Shows similar characteristics to throwing.

  As shown in FIGS. 8 to 10, the ball throwing detects a larger amplitude than a human walking. For this reason, when the amplitude value is used, it is difficult to accurately discriminate between human walking and ball throwing.

  FIG. 11 is a diagram showing the waveform areas calculated from the acoustic signals of the human walking and the ball throwing shown in FIG. The horizontal axis of the graph shown in FIG. 11 indicates the number of samples of the acoustic signal, and the vertical axis indicates the value of the waveform area for one cycle. As shown in FIG. 11, the value of the waveform area for one cycle is larger when a person walks than when a ball is thrown. Therefore, by setting a value between the waveform area value obtained by human walking and the waveform area value obtained by false detection factors such as throwing a ball as an abnormality detection threshold, human walking with high accuracy Can be detected.

  As shown in FIG. 9, a waveform having a small amplitude and a long period is obtained from the impact sound of walking of a person. On the other hand, as shown in FIG. 10, a waveform having a large amplitude and a short period is obtained from the impact sound of throwing the ball.

  In the intrusion detection system according to the present embodiment, since the presence or absence of an intruder is determined using the area value between zero-cross points, which is a value for evaluating the difference in waveform characteristics obtained from such an impact sound, The presence or absence of an intruder can be determined with accuracy.

  Note that the waveform obtained from the impact sound of throwing the ball, which is a false detection factor, is characterized by a short period, that is, a high frequency as described above. Therefore, it is conceivable to prevent erroneous detection of a ball throwing impact sound as a human walk by removing a high-frequency signal with a low-pass filter.

  FIG. 12 shows an acoustic signal after the high-frequency component has been removed by the low-pass filter, and shows a waveform after processing the acoustic signal shown in FIG. As shown in FIG. 12, the acoustic signal waveform of the ball throwing includes not only a high frequency component but also a waveform with a long period, that is, a low frequency component. For this reason, the impact sound resulting from the throwing of the ball cannot be removed only by applying the low pass filter.

  Furthermore, as shown in FIG. 10, in the impact sound resulting from the throwing of the ball, a low frequency component is obtained, but as shown in FIG. 10, only the waveform for half a period is detected for the low frequency component. . On the other hand, as shown in FIG. 9, a low-frequency waveform, that is, a waveform with a long period, is detected for one period in human walking. Therefore, in this embodiment, the waveform area calculation unit 103 calculates the area for one cycle as the waveform area, and the abnormality determination unit 104 is based on the area for one cycle in order to distinguish these accurately. To determine if there is an abnormality. As a result, it is possible to detect a person's walking with higher accuracy by determining it as a false detection factor.

  The intrusion detection device according to the present embodiment includes a control device such as a CPU, a storage device such as a ROM (Read Only Memory) and a RAM, an external storage device such as an HDD and a CD drive device, and an input / output device. The hardware configuration uses a normal computer.

  The program executed by the intrusion detection apparatus according to the present embodiment is a file in an installable format or an executable format, and is a computer such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk). It is recorded on a readable recording medium and provided. In addition, the program executed by the intrusion detection apparatus of the present embodiment may be configured to be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. Further, the program executed by the intrusion detection device according to the present embodiment may be provided or distributed via a network such as the Internet. Further, the program executed by the intrusion detection device of the present embodiment may be configured to be provided by being incorporated in advance in a ROM or the like.

  The program executed by the intrusion detection device of the present embodiment has a module configuration including the above-described units (AD conversion unit, zero cross point detection unit, waveform area calculation unit, abnormality determination unit, alarm output unit), As actual hardware, a CPU (processor) reads out a program from the storage medium and executes the program, so that each unit is loaded on the main storage device, and each unit is generated on the main storage device.

  As another example, the above-described units (AD conversion unit, zero cross point detection unit, waveform area calculation unit, abnormality determination unit, alarm output unit) may be realized by hardware.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, you may delete some components from all the components shown by embodiment. Furthermore, the constituent elements over different embodiments may be appropriately combined. Further, various modifications as exemplified below are possible.

  In the present embodiment, the waveform area calculation unit 103 of the intrusion detection device 100 determines the amplitude and period length of these acoustic signal waveforms to distinguish between human walking and false detection factors such as throwing a ball. Based on this, the length in the time axis direction that is the target of waveform area calculation used for abnormality determination is set as one period of the waveform, but the length in the time axis direction that is the target of waveform area calculation is the detection target. It can be changed as appropriate based on the characteristics of the impact sound that is a false detection factor that is assumed to be an impact sound.

  For example, the waveform area calculation unit 103 may calculate a waveform area for a half cycle, and the abnormality determination unit 104 may determine whether there is an abnormality based on the waveform area for a half cycle, or as another example. The waveform area calculation unit 103 may calculate a waveform area having a period longer than one period.

  As another example, the intrusion detection device 100 may calculate an abnormality detection threshold based on an acoustic signal detected by a walking test. Here, the walking test is a method in which a person actually walks under the same conditions as during guarding, and this walking is detected by the acoustic tube sensor 400. Based on the detection result, intrusion occurs during guarding by the intrusion detection system. An abnormality detection threshold used in the detection device 100 is set.

  Specifically, the intrusion detection apparatus 100 further includes an abnormality detection threshold value calculation unit (not shown) that calculates an abnormality detection threshold value, and the abnormality detection threshold value calculation unit has a waveform based on an acoustic signal detected during the walking test. Calculate the area. The calculation method of the waveform area is the same as the calculation method of the waveform area by the waveform area calculation unit 103.

αは予め設定された０以上１未満の値であり、αは例えば０．９に設定されている。また、Ｎは１周期分の波形面積の個数である。 The abnormality detection threshold value calculation unit further calculates N waveform areas (Area (n)) for one period obtained in the walking test, and N signal power areas (Area (n)) are calculated according to (Equation 6). Is multiplied by the sensitivity adjustment coefficient (α) of the abnormality detection threshold value to calculate the abnormality detection threshold value (Th).

α is a preset value between 0 and less than 1, and α is set to 0.9, for example. N is the number of waveform areas for one cycle.

  In addition, if it is assumed that an illegal intruder has invaded by a sneaky foot while guarding, the walking test also causes the sneaky foot to walk, and an illegal intruder assumes an intrusion by normal walking. In the walking test, normal walking is performed. Thereby, the threshold value along the footstep sound of an actual illegal intruder can be set. In other words, illegal intruders can be detected more accurately by using the threshold value thus set.

  FIG. 13 and FIG. 14 are diagrams showing a modification of the acoustic tube sensor. In the acoustic tube sensor 400, the microphone 200 is only required to be able to collect sound at or near the openings at both ends of the tube 300, and the configuration of the acoustic tube sensor 400 is limited to the configuration shown in FIG. It is not something. For example, as shown in FIG. 13, the acoustic tube sensor 400 may include two microphones 200 provided so as to seal the openings at both ends of the tube 300. In this case, the intrusion detection apparatus 100 can further estimate the position of the sound of the object in the tube 300, correct the acoustic signal that attenuates from the estimated position, and perform an abnormality determination using the corrected acoustic signal. Moreover, as shown in FIG. 14, it is set as the structure which branches the tube 300, and the two microphones 200 may be provided so that the opening part of the both ends may be sealed.

DESCRIPTION OF SYMBOLS 100 Intrusion detection apparatus 101 AD conversion part 102 Zero cross point detection part 103 Waveform area calculation part 104 Abnormality judgment part 105 Alarm output part 110 Storage part

Claims (4)

A sensor for detecting sound;
A zero-cross point detector that detects a zero-cross point where the amplitude of the sound signal waveform of the sound detected by the sensor is zero; and
A waveform area calculation unit that calculates a waveform area that is a sum of absolute values of amplitudes of the acoustic signal waveforms between the zero-cross points;
An abnormality determination unit that compares the waveform area calculated by the waveform area calculation unit with a preset threshold value and determines that an abnormality has occurred when the waveform area is larger than the threshold value. A characteristic detection device.   The detection apparatus according to claim 1, wherein the waveform area calculation unit calculates the waveform area of the acoustic signal waveform for one period.   The sensor is an acoustic tube sensor having a hollow tube having one open end, and a sound collecting unit that is disposed at the one open end and collects sound transmitted through the hollow tube. The detection device according to claim 1 or 2. A detection method for detecting an abnormality in a detection device,
A detection step in which the sensor detects sound;
A zero-cross point detecting unit that detects a zero-cross point where the amplitude of the acoustic signal waveform of the sound detected in the detection step is zero; and
A waveform area calculating unit that calculates a waveform area that is a sum of absolute values of amplitudes of the acoustic signal waveforms between the zero-cross points; and
An abnormality determination step in which an abnormality determination unit compares the waveform area calculated in the waveform area calculation step with a preset threshold value and determines that an abnormality has occurred when the waveform area is larger than the threshold value. And a detection method comprising:

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