Wireless sensor terminal, measurement frequency setting method

Abstract

To precisely grasp a state of an object by effectively utilizing an existing sensor even if the amount of memory is limited.SOLUTION: A radio sensor terminal for collecting and measuring a sound pressure signal from a measurement object via a sensor includes: a first circuit having a bandpass filter capable of varying a frequency band passing a sound pressure signal; a second circuit that detects a sound pressure level from a waveform of a sound pressure signal in a frequency band set from the outside of the radio sensor terminal and collects a sound pressure signal for predetermined collection time at a predetermined sampling interval for each changed frequency band; and a processor that calculates a statistical value of a sound pressure signal for each collected frequency band, and sets a frequency band of a sound pressure signal used for calculating a statistical value in which distance from the center of a permissible range of the statistical value satisfies a predetermined condition as a frequency band used for measuring a measurement object from among statistical values of each frequency band obtained by calculation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wireless sensor terminal and a measurement frequency band setting method. [Background technology]

[0002] Conventionally, sensor information obtained from sensors has been collected to detect the state of objects such as equipment and structures. For example, Patent Document 1 discloses such a technology. Patent Document 1 describes that a wireless communication device 10 is a wireless communication device 10 equipped with at least an acceleration sensor 107, and is equipped with data calculation means 106 that performs predetermined calculations including a Fourier transform on acceleration data measured by the acceleration sensor 107 over a certain period of time to acquire a frequency spectrum, and transmission means 101 that transmits the frequency spectrum. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-119149 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, a vibration sensor is operated periodically for a fixed period to collect data. However, if one attempts to acquire data including the ultrasonic range with a limited memory capacity, the data collection time must be shortened. As a result, the measurement time for the collected data becomes shorter than the time it takes for the device's status to change, and the device's status cannot necessarily be grasped with high accuracy.

[0005] Furthermore, when collecting sound volumes in a specific frequency range, the characteristic frequency range differs for each object being collected, so if one were to try to obtain the sound volumes in the characteristic frequency range for all objects, it would be necessary to build a sensor specialized for a specific application through pre-learning and circuit adjustment.

[0006] The present invention aims to provide a technology that can effectively utilize existing sensors and accurately grasp the state of an object even when the memory capacity is limited. [Means for solving the problem]

[0007] The wireless sensor terminal of the present invention is a wireless sensor terminal that collects and measures sound pressure signals from a measurement object via a sensor, and is configured as a wireless sensor terminal characterized by having: a first circuit having a band-pass filter that can change the frequency band that passes the sound pressure signal; a second circuit that detects the sound pressure level from the waveform of the sound pressure signal in the frequency band set from outside the wireless sensor terminal, and collects the sound pressure signal for a predetermined collection time at predetermined sampling intervals for each of the changed frequency bands; and a processor that calculates statistical values ​​of the sound pressure signals for each of the collected frequency bands, and sets the frequency band of the sound pressure signal used in calculating the statistical value, among the statistical values ​​for each of the frequency bands obtained by the calculation, whose distance from the center of the allowable range of the statistical value satisfies a predetermined condition, as the frequency band to be used for measuring the measurement object. [Effects of the Invention]

[0008] According to the present invention, even when memory capacity is limited, it is possible to effectively utilize existing sensors and accurately grasp the state of an object. Problems, configurations, and effects other than those described above will become clear from the following description of the embodiment of the invention. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating an example of a configuration of a wireless sensor terminal according to the present embodiment. [Figure 2] 10 is a flowchart showing the procedure of a process (sound pressure measurement process) performed by the wireless sensor terminal. [Figure 3] FIG. 10 is a diagram for explaining the concept of the processes from S203 to S206. [Figure 4]FIG. 10 is a diagram illustrating the concept of the process in S207. [Figure 5] 3 is a diagram showing an example of the results of simulating the operation of the sound pressure measurement process shown in FIG. 2 using actual data. [Figure 6] 3 is a diagram for explaining the relationship between data (raw data) showing the time transition of the actual sound pressure of the object to be measured detected by the sound pressure sensor S1 and the results of a simulation performed by the sound pressure measurement process shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0011] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0012] In the following explanation, various types of information may be described using expressions such as "database," "table," and "list," but the various types of information may also be expressed in data structures other than these. To indicate that the information is not dependent on the data structure, "XX table," "XX list," etc. may be referred to as "XX information." When describing identification information, expressions such as "identification information," "identifier," "name," "ID," and "number" are used, and these are interchangeable.

[0013] When there are multiple components with the same or similar functions, they may be described using the same reference numeral with different subscripts. However, when there is no need to distinguish between these multiple components, the subscripts may be omitted.

[0014] Furthermore, in the following description, processing performed by executing a program may be described, but the program is executed by a processor (e.g., a CPU or a GPU (Graphics Processing Unit)) to perform the specified processing while appropriately using storage resources (e.g., memory) and / or interface devices (e.g., communication ports), and therefore the processor may be the subject of the processing. Similarly, the subject of the processing performed by executing a program may be a controller, device, system, computer, or node having a processor. The subject of the processing performed by executing a program may be any computing unit, and may include a dedicated circuit (e.g., an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit)) that performs specific processing.

[0015] A program may be installed on a device such as a computer from a program source. The program source may be, for example, a program distribution server or a computer-readable storage medium. If the program source is a program distribution server, the program distribution server may include a processor and storage resources for storing the program to be distributed, and the processor of the program distribution server may distribute the program to be distributed to other computers. Also, in the following description, two or more programs may be realized as one program, and one program may be realized as two or more programs. [Example]

[0016] An embodiment of a wireless sensor terminal and a measurement frequency setting method according to the present invention will be described below.

[0017] 1 is a diagram showing an example of the configuration of a wireless sensor terminal according to this embodiment. The wireless sensor terminal 1000 according to this embodiment includes a frequency-variable BPF (Band-pass filter) circuit 101 connected to an acoustic wave sensor S1 for detecting the state of an object to be measured, a sound pressure detection circuit 102 for detecting a sound pressure signal in a frequency band output from the frequency-variable BPF circuit 101, an AD converter 103 for digitally converting the sound pressure signal detected by the sound pressure detection circuit 102, an MCU (Micro Controller Unit) 104 for inputting the digital sound pressure signal converted by the AD converter 103 and for executing processes performed by the wireless sensor terminal 1000, such as statistical processing and measurement processing of the input sound pressure signal, and a wireless interface (I / F) 105 for receiving various settings for the wireless sensor terminal 1000 from a user terminal T1. The MCU 104 includes a microprocessor 1041 for performing the following control and processing, and a memory 1042 for storing various data. In the following, the case where the object to be detected by the sonic sensor S1 is a device or equipment such as a hydrogen production device or a mass analyzer is exemplified, but the sonic sensor S1 can be applied to any object that can detect sound pressure or volume, such as a structure. Also, although the case where the sonic sensor S1 is used is exemplified below, a vibration sensor that detects touch or a microphone sensor that detects hearing, among the five senses, may also be used.

[0018] The frequency variable BPF circuit 101 is a circuit having a band-pass filter that can change the pass frequency band, and is a filter circuit that passes sound pressure signals of a predetermined wavelength among the sound pressure signals detected by the sound wave sensor S1 and removes noise from the passed sound pressure signals. In this example, sound pressure signals of 5 kHz to 80 kHz are passed, but any frequency may be passed depending on the usage environment.

[0019] The sound pressure detection circuit 102 is a circuit that detects the sound pressure level from the sound pressure waveform, and collects the sound pressure signal that has been filtered and noise-removed by the frequency-variable BPF circuit 101 at predetermined sampling intervals for a predetermined collection time.

[0020] The AD converter 103 converts the sound pressure signal collected by the sound pressure detection circuit 102 at predetermined sampling intervals into a digital signal.

[0021] The MCU 104 performs statistical processing such as the average value and variance of the collected sound pressure signals that have been digitally converted by the AD converter 103, and also performs sound pressure measurement processing. Specific processing performed by the MCU 104 will be described later.

[0022] The wireless I / F 105 receives settings and instructions for the wireless sensor terminal 1000 from the outside and outputs them to the MCU 104. For example, the wireless I / F 105 receives a measurement mode and set parameters specified by an input / output I / F 111 of a user terminal T1, which is another external terminal operated by a user and capable of wireless communication, via the wireless I / F 112 of the user terminal T1. The input / output I / F 111 of the user terminal T1 receives an instruction as to which measurement mode to use, for example, an analysis mode in which statistical processing of collected sound pressure signals is performed, or a monitoring mode in which sound pressure signals measured in the analysis mode are monitored. The wireless I / F 105 also receives parameters input from the input / output I / F 111 of the user terminal T1, such as (1) the bandwidth and frequency range of the frequency band that the frequency variable BPF circuit 101 passes through, (2) the collection time for analysis (e.g., several seconds to several minutes), (3) the selection conditions for the collection target (maximum and minimum values ​​of the average value (RMS), maximum and minimum values ​​of the variance, and their respective tolerance ranges), and (4) the collection time during monitoring (e.g., 0 to 10 seconds) and the measurement interval (e.g., twice a day), via the wireless I / F 112 of the user terminal T1. The user terminal T1 can be, for example, a smartphone or a tablet terminal.

[0023] As will be described in detail later, in the analysis mode immediately after the sonic sensor S1 is installed, the MCU 104 calculates the average value and variance of the sound pressure while sweeping the passband using parameters specified by the external user terminal T1 via wireless communication via the wireless I / F 105. Furthermore, the MCU 104 sets, as the measurement target, the sound pressure signal of the sound pressure level of the band with the maximum or minimum average value and the maximum or minimum variance from the collected sound pressure signals of the sound pressure levels of each band. Then, in the monitoring mode in which measurements are performed constantly, the sound pressure signal of the band to be measured that was set as the measurement target in the analysis mode is measured. The collection time and measurement interval are determined using parameters specified by the external user terminal T1 via wireless communication via the wireless I / F 105.

[0024] 2 is a flowchart showing the procedure of the process (sound pressure measurement process) performed by the wireless sensor terminal 1000. As shown in Fig. 2, the wireless sensor terminal 1000 first receives, via the wireless I / F 105, an analysis mode designated as the measurement mode from the user terminal T1 operated by the user, and sets the measurement mode to "analysis mode" (S201). Here, along with the designation of the analysis mode, the wireless sensor terminal 1000 also accepts input of the start frequency fa (Hz) at which measurement begins, the end frequency fb (Hz) at which measurement ends, the bandwidth Δf (Hz) of the frequency to be measured, and the collection time Ta (sec) for the sound pressure to be measured.

[0025] The MCU 104 changes the frequency of the sound pressure signal that is passed through the frequency variable BPF circuit 101 in steps of Δf between the start frequency fa (Hz) and the end frequency fb (Hz), such as frequency fa+bandwidth Δf (Hz), frequency fa+(2×bandwidth Δf (Hz)), frequency fb−(2×bandwidth Δf (Hz)), and frequency fb−(bandwidth Δf (Hz)) (S202).

[0026] The MCU 104 collects the sound pressure signals of the frequency changed in S202 at a predetermined sampling interval for a collection time Ta (sec) (S203). The MCU 104 calculates the average value and variance of the sound pressure signals of the frequency collected in S203 (S204), and stores them in the memory 1042 in association with the sound pressure signal of the current frequency set in S202 (S205).

[0027] The MCU 104 determines whether the frequency being changed has reached the end frequency fb (Hz) (S206), and if it determines that the frequency being changed has not reached the end frequency fb (Hz) (S206; No), it returns to S203 and changes the frequency to the frequency to which the next bandwidth Δf (Hz) has been added.

[0028] On the other hand, if the MCU 104 determines that the frequency being changed has reached the end frequency fb (Hz) (S206; Yes), it determines the measurement frequency band based on the distance from the center of the allowable range of the average value and variance of the sound pressure signal for each frequency stored in the memory 1042 in S203 to S206 (S207).

[0029] The concept of the processing from S203 to S206 will be explained below. In Fig. 3, an object to be measured (for example, a hydrogen production device or a mass spectrometer) performs operations 301a, 301b, 301c, etc. in that order, with idle operations 302a, 302b, 302c, 302d, etc. performed between each operation. When the object to be measured performs such operations, in analysis mode, each band from the start frequency fa (Hz) to the end frequency fb (Hz) is measured for at least a period longer than the time change of each of operations 301a, 301b, 301c, and the average value and variance of the sound pressure in each band are calculated (S203 to S207).

[0030] In S206, the MCU 104 plots the calculated values ​​on a plane with the average value on the vertical axis and the variance on the horizontal axis, as shown in Fig. 4. For example, as shown in Fig. 4, the MCU 104 receives the center O of the allowable range of the average value and variance on the plane input from the external user terminal T1, divides the plane into four quadrants 401A, 401B, 401C, and 401D with the allowable range center O as the center point, and sets the allowable range of the average value and the allowable range of the variance in each quadrant. Thereafter, the MCU 104 sets the allowable range of the average value and the allowable range of the variance in each set quadrant as the target range 402 (the range indicated by the dashed dotted line in Fig. 4) for determining the measurement frequency band. The example in Fig. 4 illustrates a case where the same range is set from the allowable range center O in each quadrant, but the set range of each quadrant may be different depending on the state of the object to be measured.

[0031] Of the points 403X where the calculated values ​​are plotted and which are within the four quadrants and within the target range 402, the MCU 104 selects the point where the vector from the center O of the allowable range has the largest value as the band to be measured. In this example, 17 points representing the average value and variance of the sound pressure calculated in each band are plotted. The MCU 104 selects the target candidate points 403A, 403B, 403C, and 403D from each of the four quadrants 401A, 401B, 401C, and 401D that have the largest value from the center O of the allowable range.

[0032] The MCU 104 selects one quadrant and target candidate point from the target candidate points 403A, 403B, 403C, and 403D, and transmits the result to the external user terminal T1. The input / output I / F 111 of the user terminal T1 displays the result on the screen of the terminal. At this time, the MCU 104 also transmits data (e.g., the sound pressure when the target candidate point 403B was calculated) stored in the memory 1042 in association with the one quadrant and target candidate point (e.g., an area including the quadrant 401B, the target candidate point 403B, and another point 403X in the quadrant 401B) to the user terminal T1. When the input / output I / F 111 of the user terminal T1 receives a selection operation, such as a touch operation, of a target candidate point included in the displayed result from the user, the input / output I / F 111 displays the data corresponding to the target candidate point on the screen. This allows the user to confirm the temporal transition of the sound pressure signal corresponding to the target candidate point. The state of the data will be described later using Figures 5 and 6.

[0033] The selection of the quadrant and the target candidate point may be performed according to the type of the sonic wave sensor S1 and the type of the measurement object. Also, in this example, the case where the MCU 104 selects one quadrant and one target candidate point from four quadrants and one target candidate point according to the type of the sound pressure sensor S1 has been described, but the four quadrants and the target candidate points may be output to the input / output I / F 111 of the external user terminal T1, and the user may select one of them.

[0034] In quadrant 401A shown in FIG. 4, both the change in sound pressure and the average are large relative to the center O of the allowable range, and it can be determined that the sound is due to normally-on device operation. Therefore, by detecting the sound pressure in that band, it is possible to detect an abnormality in the operation of the object to be measured. Also, in quadrant 401B shown in FIG. 4, the change in sound pressure is large and the average is small relative to the center O of the allowable range, and it can be determined that the sound is due to normally-off device operation. Therefore, as in the case of quadrant 401A, by detecting the sound pressure in that band, it is possible to detect an abnormality in the operation of the object to be measured. Furthermore, in quadrant 401C shown in FIG. 4, both the change in sound pressure and the average are small relative to the center O of the allowable range, and if there is no sound (or a faint volume below a certain level) during normal operation, it can be determined that some kind of abnormality has been detected because a certain degree of change in sound pressure has occurred relative to the silence or faint volume. 4, the sound pressure changes little and the average is large relative to the center O of the allowable range, and it can be determined that there are signs of an abnormality because the steadily occurring sound pressure changes at a constant rate. This determination can be made by checking the time progression of the sound pressure signals for each frequency stored in memory 1042 in association with each plotted point.

[0035] 2, when the MCU 104 determines the measurement frequency band in S207, it switches to "monitoring mode" as the measurement mode and notifies the external user terminal T1 operated by the user of this (S208). At this time, the MCU 104 accepts input of the sound pressure collection time Tb (sec) and measurement interval Tc (sec) from the external user terminal T1.

[0036] After waiting for the input measurement interval Tc (sec) (S209), the MCU 104 measures the sound pressure for the input collection time Tb (sec) in the measurement frequency band determined in S207 (S210), and transmits the sound pressure measurement results to the external user terminal T1 via the wireless I / F 105 (S211).

[0037] Fig. 5 is a diagram showing an example of the results of simulating the operation of the sound pressure measurement process shown in Fig. 2 using actual data. In Fig. 5, the target range for determining the frequency band to be measured is not shown.

[0038] As in the case of FIG. 4, the MCU 104 selects points 503A, 503B, 503C, and 503D in each of the four quadrants 501A, 501B, 501C, and 501D where the vector from the center O of the allowable range has the largest value as the band to be measured. Furthermore, among points 503A, 503B, 503C, and 503D, the MCU 104 selects the point where the vector has the largest value (point 503B in this example). In other words, the object to be measured shown in FIG. 5 detects sound pressure with the variance and mean of the value shown at point 503, so it can be determined that an abnormality due to normally-off equipment operation has occurred. Graphs 504A, 504B, 504C, and 504D shown in FIG. 5 show the temporal progression of sound pressure collected in the band when the above points 503A, 503B, 503C, and 503D were calculated. These graphs can be created from the sound pressure collected in S203. As explained in Figure 4, by displaying such a graph on the input / output I / F 111 of the user terminal T1, the user can grasp at a glance the state of the object to be measured and what abnormalities have occurred.

[0039] FIG. 6 is a diagram illustrating the relationship between data (raw data) showing the temporal transition of sound pressure of an actual measurement object detected by sound pressure sensor S1 and the results of a simulation using the sound pressure measurement process shown in FIG. 2. The upper part of FIG. 6 shows the raw data. By executing the sound pressure measurement process shown in FIG. 2, sound pressure in a predetermined band can be extracted from the raw data at a predetermined sampling interval, as shown in the lower part of FIG. 6. As a result, the volume of the selected band can be detected with a predetermined number of samples, making it possible to detect the characteristics of the measurement object with 1 / 96,000 the data volume compared to when using the raw data. In this example, the raw data, which was 192 Kbytes / sec, has been significantly compressed to 2 bytes / sec. However, it can be seen that characteristic bands 601, 602, and 603, which indicate the operating sound of the measurement object, can still be detected just as easily as with the raw data.

[0040] As described above, in this embodiment, as explained in Figs. 1 and 2 etc., the wireless sensor terminal 1000 that collects and measures sound pressure signals from a measurement object (for example, a hydrogen production device or a mass spectrometer) via a sensor (sound wave sensor S1), includes a first circuit (frequency variable BPF circuit 101) having a band pass filter that can change the frequency band that passes the sound pressure signal, and a circuit that detects a sound pressure level from the waveform of the sound pressure signal in the frequency band set from outside the wireless sensor terminal, and that collects the sound pressure signal for a predetermined collection time (Ta( The system further includes a second circuit (sound pressure detection circuit 102) that collects sound pressure signals at a predetermined sampling interval for a period of time (seconds), and a processor (MCU 104) that calculates statistical values ​​(average and variance of the sound pressure signals) of the sound pressure signals for each of the collected frequency bands and sets the frequency band of the sound pressure signals used to calculate the statistical value for which the distance from the center of the allowable range (the allowable range center O) of the statistical value satisfies a predetermined condition (e.g., the condition that the distance is the maximum) as the frequency band to be used for measuring the object to be measured. This allows for the effective use of existing sensors and accurate understanding of the object's condition, even when memory capacity is limited. For example, by quantifying information that is difficult to visualize, such as a gas leak from a hydrogen production plant, highly accurate monitoring of the equipment condition can be performed. Furthermore, since the frequency band is set externally via wireless communication, remote monitoring of the object to be measured is possible via a public wireless network using an existing user interface. Furthermore, by not providing such a user interface on the wireless sensor terminal itself, long-term operation using a battery, for example, is possible.

[0041] 1 and 2, the processor accepts the setting of the frequency band from the user terminal T1 wirelessly connected to the wireless sensor terminal, thereby enabling the user to set the frequency band from a terminal that the user is familiar with.

[0042] 1 and 2, the processor outputs the set frequency bands to be used for measuring the object to be measured and the collected sound pressure signals in the frequency bands to the user terminal, thereby allowing the user to check the state of the object to be measured in detail in each frequency band.

[0043] 4, 5, etc., the processor sets the frequency band of the sound pressure signal used in calculating the statistical value for which the distance is maximum as the predetermined condition as the frequency band to be used for measuring the object to be measured. This makes it possible to set the frequency band that causes the most characteristic phenomenon of the object to be measured as the frequency band to be used for measuring the object to be measured.

[0044] 1, 4, 5, etc., the processor outputs the frequency bands of the sound pressure signals used to calculate the statistical values ​​that satisfy the predetermined conditions and the collected sound pressure signals of the frequency bands to the user terminal, for example, as shown by points 503A, 503B, 503C, and 503D and graphs 504A, 504B, 504C, and 504D in Fig. 5, and sets the frequency bands selected by the user terminal as the frequency bands to be used for measuring the object to be measured. This allows the user to set a desired frequency band as the frequency band to be used for measuring the object to be measured while checking in detail the state of the object to be measured in each frequency band.

[0045] The present invention is not limited to the above-described embodiments as they are, and in the implementation stage, the components can be modified and embodied within the scope of the gist of the present invention, or multiple components disclosed in the above-described embodiments can be appropriately combined. [Explanation of symbols]

[0046] 1000 wireless sensor terminals 101 Variable frequency BPF circuit 102 Sound pressure detection circuit 103 AD converter 104 MCU 105 Wireless I / F 1041 microprocessor 1042 memory S1 ultrasonic sensor

Claims

1. A wireless sensor terminal that collects and measures sound pressure signals from a measurement object via a sensor, a first circuit having a band-pass filter capable of varying a frequency band through which the sound pressure signal passes; a second circuit that detects a sound pressure level from a waveform of the sound pressure signal of the frequency band set from outside the wireless sensor terminal, and collects the sound pressure signal at a predetermined sampling interval for a predetermined collection time for each of the changed frequency bands; a processor that calculates a statistical value of the sound pressure signal for each of the collected frequency bands, and sets the frequency band of the sound pressure signal used to calculate the statistical value whose distance from the center of the allowable range of the statistical value satisfies a predetermined condition, as the frequency band to be used for measuring the measurement object; A wireless sensor terminal comprising:

2. the processor accepts a setting of the frequency band from a user terminal wirelessly connected to the wireless sensor terminal; The wireless sensor terminal according to claim 1 .

3. The processor outputs the set frequency band used for measuring the measurement object and the collected sound pressure signal in the frequency band to the user terminal.

3. The wireless sensor terminal according to claim 2.

4. the processor sets, as the predetermined condition, the frequency band of the sound pressure signal used in calculating the statistical value in which the distance is maximum, as the frequency band to be used in measuring the measurement object. The wireless sensor terminal according to claim 1 .

5. the processor outputs the frequency band of the sound pressure signal used to calculate the statistical value that satisfies the predetermined condition and the collected sound pressure signal of the frequency band to the user terminal, and sets the frequency band selected by the user terminal as the frequency band to be used for measuring the object to be measured.

3. The wireless sensor terminal according to claim 2.

6. A measurement frequency setting method performed by a wireless sensor terminal that collects and measures sound pressure signals from a measurement object via a sensor, comprising: A frequency band through which the sound pressure signal is passed is set to be variable, When detecting a sound pressure level from a waveform of the sound pressure signal of the frequency band set from outside the wireless sensor terminal, the sound pressure signal is collected at a predetermined sampling interval for a predetermined collection time for each of the changed frequency bands, calculating a statistical value of the sound pressure signal for each of the collected frequency bands, and setting the frequency band of the sound pressure signal used to calculate the statistical value, of which the distance from the center of the allowable range of the statistical value satisfies a predetermined condition, as the frequency band to be used for measuring the measurement object; A measurement frequency setting method comprising:

7. accepting a setting of the frequency band from a user terminal wirelessly connected to the wireless sensor terminal; 7. The measurement frequency setting method according to claim 6.

8. outputting the set frequency band used for measuring the object to be measured and the collected sound pressure signal in the frequency band to the user terminal; 8. The measurement frequency setting method according to claim 7.

9. the predetermined condition is to set the frequency band of the sound pressure signal used in calculating the statistical value for which the distance is maximum as the frequency band to be used in measuring the measurement object.

7. The measurement frequency setting method according to claim 6.

10. outputting the frequency band of the sound pressure signal used in calculating the statistical value that satisfies the predetermined condition and the collected sound pressure signal of the frequency band to the user terminal, and setting the frequency band selected by the user terminal as the frequency band to be used for measuring the object to be measured; 8. The measurement frequency setting method according to claim 7.

Images