Noise avoidance method for space monitoring device using acoustic signals

Abstract

The present invention discloses a noise avoidance method for a space monitoring device using acoustic signals, which enables a space monitoring device that monitors the spatial situation using acoustic signals to avoid noise in the monitored space and accurately grasp the spatial situation.

Description

[Technical Field]

[0001] The present invention relates to a technology for a space monitoring device that monitors a space situation using an acoustic signal, which can accurately grasp the space situation while avoiding noise in the monitored space. [Background technology]

[0002] CCTV, IR cameras, vibration sensors, gas sensors, etc. are used to detect intrusion by outsiders into indoor spaces, fire outbreaks, gas leaks, etc. In the case of conventional technologies, a separate sensing device is required for each situation, such as intrusion, fire, gas, etc., so in order to monitor various indoor space situations, many sensing devices are required, which results in problems such as high costs for building equipment and considerable power consumption.

[0003] To solve these problems, a technology has recently been proposed that emits an acoustic signal and identifies the indoor space situation based on changes in the received acoustic signal.

[0004] A sound field sensor is one of the technologies that grasps spatial situations based on acoustic signals. The sound field sensor (SOFIS) is a device that emits sounds (acoustic signals) of various frequencies and analyzes changes in the sound field formed in a certain space to measure the movement of objects, air flow, temperature changes, etc. within a certain space.

[0005] When such a sound field sensor is used to grasp a spatial situation, if noise occurring temporarily or continuously in the space is mixed with the received acoustic signal, an error occurs in grasping the spatial situation.

[0006] For example, noise may cause an error in which a specific situation that did not actually occur is mistakenly determined to have occurred in the space, or noise may cause an error in which an emergency situation does not occur but is not recognized.

[0007] Such recognition errors can completely reduce the reliability of the sound field sensor's spatial monitoring operation. Therefore, a method for processing noise is needed to achieve more accurate and reliable spatial situation detection. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been devised to solve the above-mentioned problems of the prior art, and aims to solve the problem of errors occurring in grasping the spatial situation when noise occurring temporarily or continuously in the monitored space is mixed with the received acoustic signal.

[0009] In particular, the present invention aims to solve the problem of noise causing errors in which a specific situation that has not actually occurred is mistakenly determined to have occurred in a given space, and to solve the problem of noise causing errors in which an emergency situation occurs but is not recognized.

[0010] The objects of the present invention are not limited to those described above, and other objects and advantages of the present invention not described above can be understood from the following description. [Means for solving the problem]

[0011] According to an embodiment of the noise avoidance method for a space monitoring device of the present invention, the method may include an acoustic signal emitting step of emitting an acoustic signal into a target space, an acoustic signal receiving step of receiving the acoustic signal from the target space, a noise evaluation step of determining a noise section of the received acoustic signal, and a situation determination section extraction step of extracting a section of the received acoustic signal excluding the noise section as a situation determination section. In this case, the acoustic signal receiving step may selectively receive an acoustic signal corresponding to a frequency of a specific section using an appropriate frequency filter, or may distinguish and receive acoustic signals of different frequency bands.

[0012] As an example, the noise evaluation step may divide the received acoustic signal into a plurality of predetermined judgment intervals and evaluate the noise, and the situation judgment interval extraction step may extract an interval from the plurality of judgment intervals that is determined to have no noise or relatively little noise as the situation judgment interval.

[0013] As an example, the noise evaluation step may evaluate the noise in the received acoustic signal by comparing the received acoustic signal with a specific reference signal.

[0014] In this case, the method of comparing the received acoustic signal with the reference signal may evaluate noise by comparing the envelope of the received acoustic signal with the envelope of the reference signal, or may evaluate noise based on the spectrum of the received acoustic signal after converting the received acoustic signal received in the time domain into a spectrum in the frequency domain through Fourier transform or fast Fourier transform.

[0015] In another embodiment, the noise evaluation step can evaluate the noise in the received acoustic signal by determining the reception strength of frequency components other than the emitted acoustic signal frequency in the received acoustic signal.

[0016] In another embodiment, the acoustic signal emitting step may periodically emit an acoustic signal, the acoustic signal receiving step may receive an acoustic signal from the target space in a time interval including an activation time interval in which the acoustic signal is emitted and a pause time interval in which the acoustic signal is not emitted, and the noise evaluating step may evaluate noise in the received acoustic signal in the activation time interval based on the received acoustic signal received in a pause time interval before and after the activation time interval.

[0017] As a next step after the situation determination section extraction step, the spatial situation of the target space may be determined using the acoustic signals received in the extracted situation determination section, in which case the entire acoustic signals received in the extracted situation determination section may be used, or a portion of the acoustic signals may be used.

[0018] Furthermore, it is also possible to combine a plurality of extracted situation judgment sections to create a new situation judgment section, and to judge the spatial situation of the target space using the acoustic signal of the newly created situation judgment section. [Effects of the Invention]

[0019] According to the present invention, the spatial situation of the monitored space can be determined by avoiding noise sections in the received acoustic signal, thereby further improving the accuracy and reliability of the space monitoring device.

[0020] Furthermore, various noise evaluation methods such as envelope analysis and bandpass filtering may be selectively or combinedly applied to the received acoustic signal to more precisely avoid noise sections in the received acoustic signal.

[0021] The effects of the present invention are not limited to those described above, and other effects not described above will be clearly understood by those skilled in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0022] [Figure 1] 1 shows a configuration diagram of an embodiment of a space monitoring device to which the present invention is applied; [Figure 2] 1 shows a configuration diagram of an embodiment of a noise avoidance unit in a space monitoring device to which the present invention is applied. [Figure 3] 1 shows a flowchart of an embodiment of a method for monitoring a target space by noise avoidance in a space monitoring device according to the present invention. [Figure 4] 1 shows a flowchart of an embodiment of a process for avoiding noisy acoustic signals in the present invention. [Figure 5] 1 shows an example of dividing a received complex sound signal into a plurality of decision intervals in the noise avoidance method according to the present invention. [Figure 6] 1 shows an example of dividing a received complex sound signal into a plurality of decision intervals in the noise avoidance method according to the present invention. [Figure 7] 1 shows an example of dividing a received complex sound signal into a plurality of decision intervals in the noise avoidance method according to the present invention. [Figure 8] 1 shows an example of dividing a received complex sound signal into a plurality of decision intervals in the noise avoidance method according to the present invention. [Figure 9] 1 shows an example of dividing a received complex sound signal into a plurality of decision intervals in the noise avoidance method according to the present invention. [Figure 10] 1 shows an example of dividing a received acoustic signal of a single sound whose frequency changes over time into a plurality of decision intervals in a noise avoidance method according to the present invention. [Figure 11] 1 shows an example of dividing a received acoustic signal of a single sound whose frequency changes over time into a plurality of decision intervals in a noise avoidance method according to the present invention. [Figure 12] 1 shows an example of dividing a received acoustic signal of a single sound whose frequency changes over time into a plurality of decision intervals in a noise avoidance method according to the present invention. [Figure 13] 3 shows an example of a reference signal in the noise avoidance method according to the present invention. [Figure 14] 3 shows an example of a reference signal in the noise avoidance method according to the present invention. [Figure 15] 1 shows an example of noise avoidance for a received acoustic signal in the presence of persistent noise in the noise avoidance method according to the present invention. [Figure 16] 1 shows an example of noise avoidance for a received acoustic signal in the presence of persistent noise in the noise avoidance method according to the present invention. [Figure 17] 1 shows an example of noise avoidance for a received acoustic signal in the presence of persistent noise in the noise avoidance method according to the present invention. [Figure 18] 1 shows an example of noise avoidance for a received acoustic signal in which temporary noise is present in the noise avoidance method according to the present invention. [Figure 19] 1 shows an example of noise avoidance for a received acoustic signal in which temporary noise is present in the noise avoidance method according to the present invention. [Figure 20]1 shows an example of noise avoidance for a received acoustic signal in which temporary noise is present in the noise avoidance method according to the present invention. [Figure 21] 1 shows an example of avoiding noise by dividing a received acoustic signal having an active time interval and a quiet time interval in a noise avoidance method according to the present invention. [Figure 22] 1 shows an example of avoiding noise by dividing a received acoustic signal having an active time interval and a quiet time interval in a noise avoidance method according to the present invention. [Figure 23] 1 shows an example of avoiding noise by dividing a received acoustic signal having an active time interval and a quiet time interval in a noise avoidance method according to the present invention. [Figure 24] 10 shows an example of generating a situation decision interval by combining a plurality of decision intervals extracted by noise evaluation in the noise avoidance method according to the present invention. [Figure 25] 10 shows an example of generating a situation decision interval by combining a plurality of decision intervals extracted by noise evaluation in the noise avoidance method according to the present invention. [Figure 26] 10 shows an example of generating a situation decision interval by combining a plurality of decision intervals extracted by noise evaluation in the noise avoidance method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited or restricted by these embodiments.

[0024] DETAILED DESCRIPTION OF THE INVENTION For the purposes of explaining the invention, its operating advantages, and objects attained by its practice, the following description will be given with reference to an example of a preferred embodiment of the invention.

[0025] First, the terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention, and singular expressions can include plural expressions unless the context clearly dictates otherwise. Furthermore, in this application, terms such as "include" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in this specification, and should be understood not to preclude the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] In the description of the present invention, if it is determined that a detailed description of related publicly known structures or functions may obscure the gist of the present invention, the detailed description will be omitted.

[0027] The present invention provides a method for monitoring a target section of a space monitoring device, which can accurately grasp the space situation by avoiding noise in the monitored section.

[0028] A space monitoring device to which the present invention is applied can emit acoustic signals into a monitored space, receive the acoustic signals from the monitored space, and grasp the space situation based on the measured frequency response of the space.

[0029] The spatial frequency response referred to in the present invention can be explained as follows: If a target space is considered as a kind of closed circuit, and an acoustic signal is emitted as an input signal and then received as an output signal, elements such as frequency-specific sound pressure or frequency-specific phase of the received acoustic signal can be defined as the "spatial frequency response."

[0030] As an example of expressing the frequency response of such a space, it can be displayed graphically with frequency on the horizontal axis and the sound pressure of the received sound on the vertical axis, and it is also possible to display the phase element on the vertical axis instead of the sound pressure element.

[0031] Since the frequency response of a space changes depending on the physical characteristics of the space, the physical situation of the space can be inferred using the frequency response of the space, and the change in the physical characteristics of the space can be understood using the pattern in which the frequency response of the space changes. By understanding the change in the physical characteristics of the space, the spatial situation occurring in the target space can be determined.

[0032] Although the space monitoring device to which the present invention is applied can grasp the space situation based on the frequency response of the space described above, when monitoring the space situation through the space monitoring device, noise in the monitored space may reduce the detection reliability of the space monitoring device. In particular, when multiple space monitoring devices are placed in adjacent spaces, acoustic signals emitted from other space monitoring devices may act as noise on a specific space monitoring device. As such, multiple space sensing devices placed to more closely monitor the monitored space may actually reduce the monitoring performance.

[0033] Therefore, the present invention aims to further improve the accuracy and reliability of the space monitoring device by proposing a method for avoiding noise in the monitored space and grasping the spatial situation of the monitored space.

[0034] FIG. 1 shows a configuration diagram of an embodiment of a space monitoring device to which the present invention is applied.

[0035] The space monitoring device 100 to which the present invention is applied may include an acoustic signal emitting unit 110, an acoustic signal receiving unit 130, an acoustic signal processing unit 150, a situation determining unit 170, a noise avoidance unit 200, and the like.

[0036] The acoustic signal emitting unit 110 can emit an acoustic signal into a target space by including a speaker 111. The acoustic signal emitting unit 110 can emit an acoustic signal of a single sound whose frequency changes over time, an acoustic signal of a complex sound having a plurality of frequency components, an acoustic signal of a complex sound whose frequency changes over time, or an acoustic signal in which a single sound and a complex sound alternate.

[0037] In addition, the acoustic signal emitting unit 110 can emit an acoustic signal through one speaker or through multiple speakers. When emitting acoustic signals through multiple speakers, the same acoustic signal can be emitted or different acoustic signals can be emitted from each speaker.

[0038] The acoustic signal receiving unit 130 can receive an acoustic signal in a target space by including a microphone 131. The acoustic signal receiving unit 130 can receive an acoustic signal via one microphone or via multiple microphones.

[0039] The acoustic signal receiving unit 130 may be disposed in the same position as the acoustic signal emitting unit 110 as a single device, or may be disposed in a different position apart from the acoustic signal emitting unit 110 .

[0040] The acoustic signal processing unit 150 may provide an acoustic signal to be emitted into a target space to the acoustic signal emitting unit 110. The acoustic signal processing unit 150 may also measure a frequency response of the space based on the acoustic signal received by the acoustic signal receiving unit 130. For example, the acoustic signal processing unit 150 may measure the frequency response of the space by converting the received acoustic signal into a frequency domain through a Fourier transform (FT) or a fast Fourier transform (FFT).

[0041] The situation determination unit 170 can determine the situation of the target space based on the frequency response of the space. When various situation changes occur in the target space, such as object movement, temperature change, or air movement, the received acoustic signal also changes, and the frequency response of the space measured based on the received acoustic signal also changes. Therefore, by analyzing the pattern in which the frequency response of the space changes over time, it is possible to determine what situation change has occurred in the target space. The situation determination unit 170 can determine the presence or absence of changes in the frequency response of the space, the degree of change, and the change pattern, etc., to determine the situation change in the monitored space.

[0042] The noise avoidance unit 200 receives the received acoustic signal from the acoustic signal receiving unit 130, determines the noise section, and extracts a section without noise or a section with relatively little noise from the received acoustic signal as a situation determination section.

[0043] For example, the noise avoidance unit 200 may determine a noise section in the received acoustic signal by comparing the received acoustic signal with a specific reference signal, where the reference signal may be set to an acoustic signal received without noise, for example.

[0044] The noise avoidance unit 200 can provide the situation determination section extracted by avoiding noise from the received acoustic signal to the acoustic signal processing unit 150.

[0045] In this way, in the present invention, a noise-free section or a section with relatively little noise is extracted from the received acoustic signal through the noise avoidance unit 200, and the spatial situation of the target space is determined based on this, thereby improving the accuracy and reliability of the space monitoring device.

[0046] Regarding the noise avoidance unit 200, FIG. 2 shows a block diagram of one embodiment of the noise avoidance unit of a space monitoring device to which the present invention is applied.

[0047] The noise avoidance unit 200 may include an acoustic signal preprocessing unit 210, a noise evaluation unit 230, a situation determination section extraction unit 250, and the like.

[0048] The acoustic signal pre-processing unit 210 can process the received acoustic signal to determine a noise section upon receiving the received acoustic signal from the acoustic signal receiving unit 130. The acoustic signal pre-processing unit 210 can divide the received acoustic signal into a plurality of determination sections to determine a noise section in the received acoustic signal.

[0049] In one embodiment, the acoustic signal pre-processing unit 210 may divide the received acoustic signal into a plurality of decision intervals based on the period of the received acoustic signal, or may divide the received acoustic signal into a plurality of decision intervals based on a preset time unit.

[0050] In another embodiment, when the acoustic signal emitting unit 110 periodically emits an acoustic signal and the acoustic signal receiving unit 130 receives an acoustic signal from the monitored space over an entire time period including an activation time period during which the acoustic signal is emitted and a pause time period during which the acoustic signal is not emitted, the acoustic signal pre-processing unit 210 can divide the plurality of judgment periods into a plurality of judgment periods by distinguishing between the activation time period during which the acoustic signal is emitted and the pause time period during which the acoustic signal is not emitted.

[0051] In another embodiment, the acoustic signal pre-processing unit 210 may divide the received acoustic signal in the time domain into a plurality of decision intervals, and convert each decision interval into a spectrum in the frequency domain via a Fourier transform or a fast Fourier transform.

[0052] The noise evaluation unit 230 can evaluate the level of noise in the received acoustic signal. The noise evaluation unit 230 can evaluate the level of noise in any section while scanning the entire received acoustic signal, or can evaluate the level of noise for a plurality of determination sections into which the acoustic signal pre-processing unit 210 divides the received acoustic signal.

[0053] The noise evaluation unit 230 can evaluate noise in the received acoustic signal for each of a plurality of determination intervals based on a reference signal. For example, the reference signal can be set to an acoustic signal received by the acoustic signal receiving unit 130 after emitting an acoustic signal from the acoustic signal emitting unit 110 in a noise-free state, and can evaluate an interval in which noise is included in the received acoustic signal by comparing the received acoustic signal with the reference signal.

[0054] One method for comparing a received acoustic signal with a reference signal is to evaluate noise through envelope analysis of the received acoustic signal. For example, an envelope for each of a plurality of decision intervals is detected, and the shape and magnitude of the detected envelope are compared with the envelope of the reference signal to evaluate noise.

[0055] As another embodiment of comparing the received acoustic signal with the reference signal, for each of a plurality of decision intervals, the received acoustic signal can be transformed into a spectrum in the frequency domain via a Fourier transform or a fast Fourier transform, and noise can be evaluated based on the spectrum of the received acoustic signal.

[0056] For example, if frequency components other than the frequency components of the emitted acoustic signal on the spectrum of the received acoustic signal are expressed as sound pressures above a certain level, it can be evaluated that noise is present. Alternatively, noise can be evaluated by comparing the spectrum of the received acoustic signal with a reference spectrum obtained by transforming a reference signal in the frequency domain.

[0057] As another embodiment of the noise evaluation unit 230, noise can be evaluated by measuring the received intensity of frequency components other than the frequency of the emitted acoustic signal using a frequency filter. For example, in a situation where there is no noise, no sound should be received in frequency ranges other than the frequency band of the emitted acoustic signal. However, if sound is received with an intensity above a certain level in frequency ranges other than the frequency band of the emitted acoustic signal, this can be regarded as noise.

[0058] This method starts from the assumption that if noise with a frequency component different from the frequency of the emitted acoustic signal is measured, it is likely that the noise also contains noise with the same frequency component as the emitted acoustic signal, or even if it does not, there is a high probability that it will cause errors in the spatial situation assessment process.

[0059] In this case, in order to grasp the reception strength of frequency components other than the emitted acoustic signal frequency, a method can be used in which the emitted frequency is separated from other frequencies using an appropriate frequency filter and received, and the reception strength of the separated latter frequency component acoustic can be measured. Alternatively, the acoustic signal received in the time domain can be converted into a frequency domain signal via Fourier transform or fast Fourier transform, and then the reception strength of frequencies other than the emitted frequency can be grasped.

[0060] In another embodiment of the noise evaluation unit 230 evaluating noise, when a determination period is divided into an active time period and a pause time period depending on whether an acoustic signal is emitted, the noise evaluation unit 230 may evaluate noise for pause time periods before and after a specific active time period and evaluate noise for the specific active time period based on the evaluation. For example, the noise evaluation unit 230 may calculate a noise level for a pause time period before a specific active time period or a pause time period after a specific active time period to evaluate noise, and if the pause time period is evaluated as a noise period, the specific active time period may be determined to be a noise period.

[0061] In the above embodiment, for convenience of explanation, the noise evaluation process has been described based on the case where the noise evaluation step is started only after the acoustic signal receiving step is completed. However, the noise evaluation step does not necessarily have to be started after the acoustic signal receiving step is completed.

[0062] For example, when evaluating noise in a specific section by performing a fast Fourier transform on the received acoustic signal for that section to measure the frequency response and then comparing the measured frequency response with a reference frequency response, the noise evaluation step for that section must necessarily be started after reception of the acoustic signal for that section is completed.

[0063] However, for example, when detecting the envelope of a received acoustic signal for a specific section and comparing it with the envelope of a reference signal to evaluate noise, the envelope comparison step may be started after reception of the acoustic signal for that specific section is complete. However, it is more preferable to start the envelope comparison step before reception of the acoustic signal for that specific section is complete. For example, suppose the step of receiving the acoustic signal for a specific section begins at t1 and ends at t2, and the step of evaluating noise for that specific section begins at t3 and ends at t4. In this case, logically, the time t4 at which noise evaluation for the specific section ends must be later than the time t2 at which reception of the acoustic signal for that specific section ends. However, the time t3 at which noise evaluation for the specific section begins does not need to be later than the time t2 at which reception of the acoustic signal ends. Rather, it is more preferable that t3 be earlier than t2 and immediately after t1. Ultimately, in this case, the step of receiving the acoustic signal and the step of evaluating noise can overlap in time. That is, logically, it is natural that the acoustic signal receiving step precedes the noise evaluation step, but physically, the acoustic signal receiving step and the noise evaluation step can be performed approximately simultaneously in time. This is similar to logically, the acoustic signal emitting step precedes the acoustic signal receiving step, but physically, the acoustic signal emitting step and the acoustic signal receiving step virtually overlap in time. That is, if the acoustic signal emitting step for a specific section starts at t5 and ends at t6, t1 virtually overlaps with t5, and t2 virtually equals t6. As a result, t1, t3, and t5 are approximately the same time, and t2, t4, and t6 are approximately the same time. In other words, (1) acoustic signal emission, (2) acoustic signal reception, and (3) noise evaluation are performed sequentially logically, but can be performed virtually simultaneously physically.

[0064] However, for the sake of convenience, the following description will be based on an embodiment in which the noise evaluation step for a specific section starts only after the acoustic signal receiving step for that section is completed.

[0065] In FIG. 2, the situation determination section extraction section 250 can extract a noise-free section or a section with relatively little noise from the received acoustic signal as a situation determination section based on the noise evaluation result from the noise evaluation section 230.

[0066] For example, if the noise evaluation unit 230 calculates a noise level for each of a plurality of judgment intervals, the situation judgment interval extraction unit 250 can extract a judgment interval having a noise level equal to or lower than a reference value as the situation judgment interval. Alternatively, the situation judgment interval extraction unit 250 can extract a judgment interval having a relatively lowest noise level as the situation judgment interval.

[0067] The extracted situation determination section is qualified to be used as data for determining the situation of the target space. Therefore, when determining the spatial situation of the target space using the acoustic signals received in the extracted situation determination section as a next step after the situation determination section extraction step, all or only a portion of the acoustic signals received in the extracted situation determination section may be used.

[0068] The situation judgment unit 170 can judge changes in the situation of the monitored space based on the situation judgment section in which the noise section in the received acoustic signal has been removed by the noise avoidance unit 200, thereby improving the accuracy and reliability of the space monitoring device 100.

[0069] The present invention provides a method for monitoring a target space by avoiding noise sections in the above-mentioned space monitoring device 100. Hereinafter, the target space monitoring method through noise avoidance according to the present invention will be described with reference to an embodiment of the space monitoring device 100 to which the present invention is applied.

[0070] FIG. 3 shows a flowchart of an embodiment of a method for monitoring a target space through noise avoidance in a space monitoring device according to the present invention.

[0071] The space monitoring device 100 may emit an acoustic signal into the monitored space (S110). Here, the space monitoring device 100 may emit into the monitored space a single sound whose frequency changes over time, a complex sound having a plurality of frequency components, a complex sound whose frequency changes over time, or an acoustic signal in which the single sound and the complex sound alternate.

[0072] Then, the space monitoring device 100 can receive an acoustic signal from the monitored space (S130).

[0073] The noise avoidance unit 200 of the space monitoring device 100 evaluates noise in a received acoustic signal (S150) and extracts a noise-free section or a section with relatively little noise from the received acoustic signal as a situation determination section (S170).

[0074] The space monitoring device 100 can determine the situation of the monitored space based on the situation determination section with less noise (S190). The situation determination unit 170 of the space monitoring device 100 can determine the situation change of the monitored space by measuring the frequency response of the space based on the acoustic signal of the situation determination section.

[0075] The process by which the noise avoidance unit 200 evaluates noise in a received acoustic signal and extracts a situation judgment section will be considered in more detail with reference to the flowchart of an embodiment shown in Figure 4. As described above, (1) acoustic signal emission, (2) acoustic signal reception, and (3) noise evaluation must be performed logically sequentially, but may be performed physically at approximately the same time. However, for convenience of explanation, Figures 3 and 4 show an embodiment in which the noise evaluation step for a specific section begins only after the acoustic signal reception step for that section is completed.

[0076] The acoustic signal pre-processing unit 210 of the noise avoidance unit 200 can process the received acoustic signal transmitted from the acoustic signal receiving unit 130 .

[0077] The acoustic signal pre-processing unit 210 can divide the received acoustic signal into a plurality of decision intervals by dividing the received acoustic signal into intervals (S151).

[0078] In relation to the process in which the acoustic signal pre-processing unit 210 of the noise avoidance unit 200 divides the received acoustic signal into a plurality of decision intervals, an example of dividing the received acoustic signal into a plurality of decision intervals in the noise avoidance method according to the present invention shown in FIGS. 5 to 12 will be considered.

[0079] It is assumed that an acoustic signal of a complex sound composed of 17 frequencies with a center frequency of 4 KHz and a frequency interval of 4 Hz is emitted, and the received acoustic signal 310 shown in FIG. 5 is received.

[0080] In one embodiment, the acoustic signal pre-processing unit 210 may divide each section into a plurality of judgment sections based on the period of the received acoustic signal. For example, as shown in FIG. 6, the received acoustic signal 310 may be divided into four sections S11 (311), S12 (312), S13 (313), and S14 (314) as judgment sections by dividing the section into 0.25-second time units based on the period of the received acoustic signal. The division of the received acoustic signal may be appropriately set to a multiple of the period.

[0081] In another embodiment, the acoustic signal pre-processing unit 210 may divide each section of the received acoustic signal into a plurality of decision sections by a predetermined time unit. For example, as shown in FIG. 7, the received acoustic signal 310 may be divided into two sections S21 (311, 312) and S22 (313, 314) by dividing the received acoustic signal 310 into 0.5-second time units.

[0082] In another embodiment, the acoustic signal pre-processing unit 210 may divide the acoustic signal into multiple judgment intervals by dividing the signal into intervals where parts of the signal overlap. For example, as shown in Figure 8, the received acoustic signal 310 may be divided into 0.5-second intervals, with some of the intervals overlapping, resulting in three judgment intervals: S23 (311, 312), S24 (312, 313), and S25 (313, 314). Alternatively, as shown in Figure 9, the received acoustic signal 310 may be divided into 0.75-second intervals, with some of the intervals overlapping, resulting in two judgment intervals: S26 (311, 312, 313) and S27 (312, 313, 314).

[0083] The total length of the received acoustic signal and the length of the individual judgment interval can be set appropriately as needed. For example, the total length of the received acoustic signal may be 5 minutes or 24 hours.

[0084] The acoustic signal pre-processing unit 210 may divide the received acoustic signal into a plurality of decision intervals and convert each decision interval into a spectrum in the frequency domain through a Fourier transform or a fast Fourier transform.

[0085] Furthermore, it is assumed that a single sound signal whose frequency changes over time is emitted and the received sound signal 410 is received for 1.5 seconds as shown in FIG.

[0086] The acoustic signal pre-processing unit 210 can divide the period of the acoustic signal into three intervals S31 (411), S32 (412), and S33 (413) as judgment intervals by dividing the period of the acoustic signal into 0.5-second intervals as shown in FIG. 11.

[0087] Alternatively, the acoustic signal pre-processing unit 210 may divide the acoustic signal into six judgment intervals S34 (414), S35 (415), S36 (416), S37 (417), S38 (418), and S39 (419) in 0.25-second time units, regardless of the period of the acoustic signal, as shown in FIG. 12 .

[0088] After the acoustic signal pre-processing unit 210 processes the received acoustic signal as necessary and divides it into a plurality of judgment intervals, the noise evaluation unit 230 of the noise avoidance unit 200 can evaluate the degree of noise for each judgment interval of the received acoustic signal and calculate the noise level (S153).

[0089] The noise evaluation unit 230 may calculate a noise level by comparing the decision interval with a reference signal. Here, the reference signal may be set based on a received acoustic signal received by the acoustic signal receiving unit 130 in a noise-free state, where the acoustic signal is emitted from the acoustic signal emitting unit 110.

[0090] As an example, FIG. 13 shows an example of a reference signal in the noise avoidance method according to the present invention.

[0091] For the received acoustic signal 310 shown in Fig. 5, when the judgment interval is divided based on the period of the received acoustic signal as shown in Fig. 6, the reference signal 320 shown in Fig. 13 can be set accordingly. The noise evaluator 230 can evaluate the noise for each judgment interval by comparing the reference signal 320 with each judgment interval.

[0092] 14 may be extracted and set as the reference envelope 325. The noise evaluation unit 230 may compare the reference envelope 325 with the envelope of each decision interval to evaluate the noise for each decision interval.

[0093] For example, the noise evaluation unit 230 may compare each decision interval with the reference signal 320 or compare the envelope for each decision interval with the reference envelope 325, and calculate the noise level according to the degree of difference.

[0094] As an example, when the acoustic signal preprocessing unit 210 converts each decision interval into a spectrum in the frequency domain, the noise evaluation unit 230 may calculate the noise level by determining whether frequency components other than the frequency components of the acoustic signal emitted on the spectrum of the received acoustic signal are represented by a sound pressure equal to or higher than a certain level, or may calculate the noise level by comparing a reference spectrum obtained by converting a reference signal in the frequency domain with the spectrum of the received acoustic signal.

[0095] Then, the situation judgment section extraction section 250 of the noise avoidance section 200 can select (S155) and extract (S170) a section without noise or a section with relatively little noise from the received acoustic signal as a situation judgment section based on the evaluation result of the noise evaluation section 230.

[0096] The process of evaluating noise in a received acoustic signal and extracting a situation judgment section will be described with reference to FIGS.

[0097] 15 and 16 show an example of noise avoidance for a received acoustic signal in the presence of persistent noise in the noise avoidance method according to the present invention.

[0098] As shown in FIG. 15, the acoustic signal pre-processing unit 210 can divide the received acoustic signal 330 received for one second into a plurality of decision intervals S41 (331), S42 (332), S43 (333), and S44 (334) based on a period of 0.25 seconds.

[0099] When the noise evaluation unit 230 evaluates noise based on the reference signal for each of the judgment intervals S41 (331), S42 (332), S43 (333), and S44 (334), it can be determined that persistent noise 335 exists in the judgment interval S41 (331) and persistent noise 336 exists across the judgment intervals S43 (333) and S44 (334), as shown in FIG. 16.

[0100] Here, noise evaluation for each judgment interval S41 (331), S42 (332), S43 (333), and S44 (334) can be performed by using a frequency filter to measure the intensity of sound received in frequency ranges other than the frequency band of the emitted acoustic signal, thereby evaluating noise for each judgment interval S41 (331), S42 (332), S43 (333), and S44 (334).

[0101] Alternatively, the noise for each of the decision intervals S41(331), S42(332), S43(333), and S44(334) can be evaluated by comparing a reference envelope extracted from the envelope for the reference signal with the envelope for each of the decision intervals S41(331), S42(332), S43(333), and S44(334).

[0102] Alternatively, for each decision interval, the received acoustic signal may be Fourier transformed or fast Fourier transformed to represent it as a spectrum in the frequency domain, and noise may be evaluated by determining whether frequency components other than the frequency components of the acoustic signal emitted on the spectrum of each decision interval are represented by sound pressures above a certain level. Alternatively, noise may be evaluated by comparing the spectrum of each decision interval with a reference spectrum obtained by transforming a reference signal in the frequency domain.

[0103] Furthermore, it is also possible to evaluate noise by selectively superimposing and applying the above-mentioned multiple evaluation methods to each decision interval.

[0104] Based on the evaluation result of the noise evaluation unit 230, the situation determination section extraction unit 250 can select a noise-free or relatively noise-free judgment section S42 (332) as the situation determination section.

[0105] 17, the situation determination section extraction unit 250 can extract S42 (332) from the received acoustic signal 330 in the situation determination section.

[0106] As another embodiment, FIGS. 18 to 20 show an example of noise avoidance for a received acoustic signal containing temporary noise in the noise avoidance method according to the present invention.

[0107] As shown in FIG. 18, the acoustic signal pre-processing unit 210 can divide the received acoustic signal 340 received for one second into a plurality of decision intervals S51 (341), S52 (342), S53 (343), and S54 (344) based on a period of 0.25 seconds.

[0108] When the noise evaluation unit 230 evaluates the noise for each of the judgment intervals S51 (341), S52 (342), S53 (343), and S54 (344), it can be determined that temporary noise 345 exists in the judgment interval S51 (341) and temporary noise 346 exists in the judgment interval S54 (343), as shown in FIG. 19.

[0109] Here, the noise evaluation for each of the decision sections S51 (341), S52 (342), S53 (343), and S54 (344) can be performed using the method described above with reference to FIG.

[0110] Based on the evaluation results of the noise evaluation unit 230, the situation judgment interval extraction unit 250 can select the judgment intervals S52 (342) and S53 (343) that are noise-free or have relatively the least noise as the situation judgment intervals.

[0111] 20, the situation determination section extraction unit 250 can extract either or both of S52 (342) and S53 (343) from the received acoustic signal 330 as situation determination sections.

[0112] As another embodiment, FIGS. 21 to 23 show an example of avoiding noise by dividing a received acoustic signal having an active time interval and a quiescent time interval in the noise avoidance method according to the present invention.

[0113] As shown in FIG. 21, when the received acoustic signal 350 received for 1.5 seconds includes an active time interval and a pause time interval, the acoustic signal pre-processing unit 210 can divide the judgment interval into the active time intervals S62 (352), S64 (354), and S66 (356) and the pause time intervals S61 (351), S63 (353), and S65 (355) in consideration of the period of the received acoustic signal.

[0114] 22, the noise evaluation unit 230 can extract the judgment intervals S61 (351), S63 (353), and S65 (355), which are pause time intervals, and evaluate noise therefrom. Since these are pause time intervals in which the acoustic signal emission unit 110 does not emit an acoustic signal, if no acoustic signal is received in these intervals, or if an acoustic signal is received but its magnitude is sufficiently small, or if the frequency of the acoustic signal is different from the frequency of the emitted acoustic signal and its influence on spatial situation judgment is small below a reference level, the noise can be evaluated as being absent or small overall.

[0115] The situation determination interval extraction unit 250 can extract the situation determination interval based on the evaluation result of the noise evaluation unit 230, and if a pause time interval before or after an activation time interval is evaluated as a noise interval, the situation determination interval extraction unit 250 can evaluate the activation time interval as a noise interval. That is, if noise exists in a pause time interval before an activation time interval or a pause time interval after an activation time interval, this indicates that noise is likely to exist in the activation time interval as well, and therefore the activation time interval can be regarded as a noise interval.

[0116] In the case of FIG. 22, the pause time periods S61 (351) and S63 (353) can be evaluated as having no noise or noise below a certain level, while the pause time period S65 (355) can be evaluated as having noise 357.

[0117] Since the pause time interval S65 (355) is evaluated as a noise interval, the active time interval S64 (354) before the pause time interval S65 (355) can be considered as a noise interval, or the active time interval S66 (356) after the pause time interval S65 (355) can also be considered as a noise time interval.

[0118] Since the active time interval S62 (352) can be evaluated as having no noise or noise below a certain level in both the preceding pause time interval S61 (351) and the following pause time interval S63 (353), the situation judgment interval extraction unit 250 can select the active time interval S62 (352) as the situation judgment interval.

[0119] 23, the situation determination section extraction unit 250 can extract S62 (352) from the received acoustic signal 350 as the situation determination section.

[0120] The embodiments described with reference to FIGS. 15 to 23 have been described with reference to the case where the emitted acoustic signal is a complex sound. However, even when the acoustic signal emitting unit 110 emits an acoustic signal of a single sound whose frequency changes over time, the noise section can be evaluated by applying the noise evaluation methods of FIGS. 15 to 23.

[0121] For example, when evaluating noise in a received acoustic signal 410 of a single sound whose frequency changes over time as shown in Figure 10, the noise can be evaluated by dividing the judgment interval into sections as shown in Figure 11 or 12 and applying the above-described noise evaluation method to each judgment interval. Then, a judgment interval with no or relatively little noise can be extracted as a situation judgment interval.

[0122] Furthermore, by performing noise evaluation on multiple judgment intervals, multiple judgment intervals with no or relatively little noise can be extracted, and the extracted multiple judgment intervals can be combined to generate a situation judgment interval synthesized into a new received acoustic signal. This will be described with reference to Figures 24 to 26.

[0123] When a received acoustic signal 420 of a single sound whose frequency changes over time as shown in FIG. 24 is acquired, the received acoustic signal 420 can be divided into a plurality of decision intervals S71 (421) to S76 (426) as described above.

[0124] For each of the decision intervals S71 (421) to S76 (426), the decision intervals S72 (422) and S75 (425) with no noise or relatively little noise can be extracted as shown in FIG. 25 through the noise evaluation described above.

[0125] Then, by combining the extracted judgment sections S72 (422) and S75 (425) in accordance with the period of the acoustic signal, it is possible to generate the situation judgment section S77 (431, 432) as the received acoustic signal 430 shown in FIG.

[0126] In this way, by extracting decision intervals that are noise-free or have relatively little noise, and synthesizing them to generate new situation decision intervals, it is possible to obtain an acoustic signal that effectively avoids noise.

[0127] Meanwhile, the total length of the received acoustic signal, the interval between the individual judgment intervals, and the number of situation judgment intervals extracted from the entire received acoustic signal can be adjusted as needed.

[0128] Meanwhile, in the above example, a method has been described in which a certain interval between judgment intervals is set in advance, noise is evaluated for each judgment interval, and a portion of the intervals is selected as the situation judgment interval. However, instead of specifying a judgment interval from the beginning, it is also possible to scan the entire received acoustic signal, extract an interval with any interval without noise, and set it as the situation judgment interval.

[0129] As described above, the present invention can determine the spatial situation of the monitored space by avoiding noise sections in the received acoustic signal, thereby further improving the accuracy and reliability of the space monitoring device.

[0130] Furthermore, various noise evaluation methods such as envelope analysis and bandpass filtering may be selectively or combinedly applied to the received acoustic signal to more precisely avoid noise sections on the received acoustic signal.

[0131] The above description merely exemplifies the technical concept of the present invention, and various modifications and variations may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments described herein are for illustrative purposes only, and are not intended to limit the technical concept of the present invention. The technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical concepts within the scope equivalent thereto should be interpreted as being within the scope of the invention.

Claims

1. A noise avoidance method for a space monitoring device that monitors changes in physical properties of a space, comprising: an acoustic signal emitting step of emitting an acoustic signal into a target space; an acoustic signal receiving step of receiving an acoustic signal of the target space; a noise evaluation step for determining a noise period in the received acoustic signal; a situation determination section extraction step of extracting a section excluding the noise section from the received acoustic signal as a situation determination section; a situation determination step of determining a spatial situation of the target space according to physical characteristics using a change in the acoustic signal received in the extracted situation determination section; Including, the acoustic signal is at least one of a single sound whose frequency changes over time, a complex sound whose frequency components change over time, a complex sound whose frequency components change over time, and an acoustic signal in which a single sound and a complex sound alternate. A noise avoidance method for a space monitoring device.

2. The noise evaluation step includes: classifying the received acoustic signal into a plurality of predetermined decision sections and evaluating noise; The situation judgment section extraction step includes:

2. The noise avoidance method for a space monitoring device according to claim 1, wherein a section determined to have no noise or relatively little noise is extracted as a situation judgment section from among a plurality of judgment sections.

3. The noise evaluation step includes:

2. The noise avoidance method for a space monitoring device according to claim 1, wherein the noise in the received acoustic signal is evaluated by comparing the received acoustic signal with a specified reference signal.

4. The noise evaluation step includes:

2. A noise avoidance method for a space monitoring device according to claim 1, wherein noise in the received acoustic signal is evaluated by grasping the reception strength of frequency components other than the frequency of the emitted acoustic signal.

5. The step of emitting an acoustic signal comprises: periodically emit an acoustic signal, The acoustic signal receiving step includes: receiving an acoustic signal of the target space in a time interval including an activation time interval during which the acoustic signal is emitted and a pause time interval during which the acoustic signal is not emitted; The noise evaluation step includes:

2. The noise avoidance method of claim 1, further comprising: evaluating noise for a received acoustic signal in an activation time interval based on received acoustic signals received in idle time intervals before and after the activation time interval.

6. The noise evaluation step includes: converting the received acoustic signal into a spectrum in the frequency domain; 2. The noise avoidance method for a space monitoring device according to claim 1, wherein noise is evaluated based on the spectrum of the received acoustic signal.

7. The noise evaluation step includes:

4. The noise avoidance method for a space monitoring device according to claim 3, wherein noise is evaluated by comparing an envelope of the received acoustic signal with an envelope of the reference signal.

8. The method further includes a situation judgment section combination step of combining the extracted plurality of situation judgment sections, The noise avoidance method for a space monitoring device according to claim 2, wherein the situation determination step determines the spatial situation of the target space using the combined acoustic signals of the situation determination section.

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