Meta-structure for improving acoustic directivity, and system comprising same

Abstract

A meta-structure for improving acoustic directivity, presented in one aspect of the present invention, is a structure for improving acoustic directivity, and comprises a tubular structure in which a hollow is formed and of which the length extends in one direction, wherein the tubular structure is open toward the inner hollow and has a slot formed perpendicular to the longitudinal direction of the tubular structure.

Description

Metastructure for enhancing acoustic directivity and system including the same

[0001] The present invention relates to a system comprising a tubular metastructure for enhancing acoustic directivity and an acoustic sensor coupled thereto. Furthermore, the invention relates to a method for enhancing acoustic directivity and estimating the direction of sound using the said system.

[0002] Acoustic directivity refers to the ability to selectively detect or amplify sounds coming from a specific direction. Today, acoustic directivity is utilized importantly in various fields such as speech recognition, environmental monitoring, robotics, and military security.

[0003] Conventional techniques for implementing acoustic directivity include array methods utilizing multiple acoustic sensors. This method operates on the principle of arranging multiple acoustic sensors at regular intervals to selectively amplify sound from a specific direction while suppressing sound from other directions. However, this approach has disadvantages, such as a large overall system size and a rapid decline in performance if the array is not precisely aligned or if the positions of some sensors are misaligned. Furthermore, there are issues where the overall system cost and installation complexity increase as the number of sensors grows.

[0004] Another conventional technique for implementing acoustic directivity involves estimating the direction of a sound source through mathematical calculations of the signal and selectively receiving only the signal from the desired direction. This method utilizes mathematical algorithms and has the limitation of requiring high-performance computing devices due to the massive amount of computation required.

[0005] Therefore, there is a need for acoustic directivity enhancement and acoustic direction estimation technologies that are small in size, require minimal computation, and can accurately estimate acoustic signals while being robust against environmental noise.

[0006] The objective of the present invention is to solve the aforementioned problems by proposing a structure and system for improving acoustic directivity that can reduce size and computational load through a miniaturized structure, thereby replacing conventional multi-array acoustic sensor methods and methods based on mathematical calculations. Furthermore, the invention aims to propose a method for improving acoustic directivity and estimating direction using the said system.

[0007] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0008] In order to solve the aforementioned problem, a metastructure for improving acoustic directivity proposed in one aspect of the present invention is a structure for improving acoustic directivity comprising a tubular structure having a hollow formed inside and a length extended in one direction, wherein the tubular structure is open toward the internal hollow and has a slot formed perpendicular to the length direction of the tubular structure.

[0009] According to one embodiment, the slots are formed in a plurality of ways with a pattern, and the plurality of slots may have the same size and length.

[0010] According to one embodiment, multiple slots having the same size and length may be formed on the same circumference of the tube.

[0011] According to one embodiment, the slot may have a length of 3 to 10 times its width.

[0012] According to one embodiment, the diameter of the tube may be 1.5 to 3 times the length of the slot.

[0013] According to one embodiment, the diameter of the tube may be 28 to 36 mm, the number of slots may be 25 to 40, and the spacing between the slots may be 3 to 7 mm.

[0014]

[0015] An acoustic directivity enhancement system comprising a metastructure proposed in another aspect of the present invention comprises: a tubular structure; and an acoustic sensor connected to the tubular structure; wherein the tubular structure has a slot formed perpendicular to the longitudinal direction of the tubular structure and is open toward an internal hollow.

[0016] According to one embodiment, the acoustic sensor may have at least a portion inserted into a tubular structure.

[0017] According to one embodiment, the acoustic sensor may further include a rotation axis connected thereto, wherein the rotation axis is perpendicular to the longitudinal direction of the tubular structure, and the tubular structure may be rotatable 360° around the rotation axis.

[0018] According to one embodiment, the acoustic sensor may include one sensor.

[0019] According to one embodiment, the system may be replaceable with another tubular structure designed to have a slot pattern different from that of the existing installed tubular structure.

[0020] According to one embodiment, the tubular structure may have a phase cancellation effect in a sound having a frequency of 2 kHz or higher.

[0021]

[0022] A method for acoustic directivity enhancement and direction estimation proposed in another aspect of the present invention comprises: a step of rotating an acoustic sensor coupled to a slotted tubular structure around a rotation axis perpendicular to the longitudinal axis of the tubular structure; a step of analyzing a specific frequency response received by the acoustic sensor for each rotation angle; and a step of setting the rotation angle at which the frequency response is maximum, corresponding to the specific frequency, as the directivity enhancement angle. The slotted tubular structure may be the metastructure.

[0023] According to one embodiment, the method may further include the step of arranging a tubular structure with a slot formed at the directivity enhancement angle and an acoustic sensor; and the step of canceling out frequencies other than the specific frequency by a phase cancellation mechanism.

[0024] According to one embodiment, the method may further include the step of estimating the location of a sound source using a signal processing algorithm for acoustic data received by the acoustic sensor according to rotation angle.

[0025] According to one embodiment, the acoustic data is a human voice, and the signal processing algorithm may be an ASR algorithm.

[0026] According to one embodiment of the present invention, acoustic directivity can be improved through a phase cancellation mechanism using a slotted metastructure, thereby effectively reducing the amount of computation required for signal processing compared to conventional technology.

[0027] In addition, since the system according to the present invention secures directivity through the rotation of a single sensor, it is possible to miniaturize it compared to conventional directivity enhancement technologies that arrange multiple sensors, and thus has the advantage of being applicable even in dynamic environments.

[0028] In addition, according to the embodiments proposed in this invention, since the theoretically calculated directional angle and the experimentally measured angle show a high degree of agreement, the directional angle for a desired frequency can be predicted and set in advance, thereby enabling precise directional control without an additional calibration process.

[0029] However, the effects of the present invention are not limited to those described above, but include all effects naturally realized through the various configurations proposed in the present invention.

[0030] FIG. 1 is a drawing illustrating a metastructure according to one embodiment of the present invention.

[0031] Figure 2 is a diagram showing the parameters of a metastructure.

[0032] FIG. 3a is a side view of an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention, and FIG. 3b is a diagram illustrating a rotation method of an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention.

[0033] FIGS. 4a and FIGS. 4b are experimental graphs related to the phase cancellation effect according to parameter changes of a metastructure according to one embodiment of the present invention.

[0034] FIG. 5 is acoustic position tracking experimental data of an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention.

[0035] Figure 6 is experimental data applied to tracking the sound locations of multiple people using an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention.

[0036] Figure 7 is experimental data according to the angle of a human voice using an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention.

[0037] FIG. 8 is a diagram illustrating experimental directional angle results measured for various frequencies for an acoustic directional enhancement system including a metastructure according to one embodiment of the present invention.

[0038] FIG. 9a is a diagram showing the theoretical directional angle compared with the experimental results of FIG. 8 for an acoustic directional enhancement system including a metastructure according to one embodiment of the present invention, and FIG. 9b is a diagram showing experimental data for confirming the minimum frequency at which directional characteristics can change according to the rotation angle in an acoustic directional enhancement system including the metastructure.

[0039] FIG. 10 is a diagram showing the comparison results between a meta-structure-based acoustic sensor according to the present invention and a sensor without the structure (free-field) condition. FIG. 11 is a table of experimental results in which an acoustic directivity enhancement system including a meta-structure according to an embodiment of the present invention is applied as a hardware bandpass filter.

[0040] FIGS. 12 to 14 are images of examples in which an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention is applied to a CNC tool failure monitoring hardware bandpass in a noisy factory environment and various experiments are performed.

[0041] FIG. 15 is an image of an example in which various experiments were performed by applying a hardware bandpass for Human-Robot interaction and Human-Machine interaction and Human speech recognition to an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention in a noisy environment.

[0042]

[0043] The embodiments of the present invention are illustrative for the purpose of explaining the technical concept of the present invention. The scope of rights according to the present invention is not limited to the embodiments presented below or the specific description thereof.

[0044] All technical and scientific terms used in this invention, unless otherwise defined, have the meaning generally understood by those skilled in the art to which this invention pertains. All terms used in this invention are selected for the purpose of further explaining this invention and are not selected to limit the scope of rights according to this invention.

[0045] Expressions such as "comprising," "having," "having," etc. used in the present invention should be understood as open-ended terms implying the possibility of including other embodiments, unless otherwise stated in the phrase or sentence containing such expressions.

[0046] In the present invention, when a part such as a layer, film, region, or plate is described as being "above" or "on" another part, this includes not only the case where it is "immediately above" another part, but also the case where there is another part in between. Conversely, when a part is described as being "immediately above" another part, it means that there is no other part in between. Furthermore, being described as being "above" or "on" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" or "on" in the direction opposite to gravity. The same applies to "below" or "under."

[0047] In the present invention, "planar view" refers to the object of the present invention as viewed from above, and "cross-sectional view" refers to the cross-section of the object of the present invention cut perpendicularly to the ground or installation surface as viewed from the side. Additionally, in the present invention, "front side" refers to the part visible from the front or front when worn, and "back side" refers to the side opposite to the "front side." Furthermore, in the present invention, "front side" refers to the side facing the front in any configuration, and "back side" refers to the side facing the back in the same configuration.

[0048] In the present invention, expressions such as "identical" and "identical" indicate not only a strictly identical state, but also a state in which tolerances or differences exist to the extent that the same function is obtained.

[0049] In the present invention, expressions indicating relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "vertically," "to the center," "concentric," or "coaxial," not only strictly indicate such arrangements but also indicate a state of relative displacement with respect to tolerances or angles or distances to the extent that the same function is obtained.

[0050] Unless otherwise stated, singular expressions described in the present invention may include the meaning of the plural form, and this applies likewise to singular expressions described in the claims.

[0051] Embodiments of the present invention will be described below with reference to the attached drawings. In this process, the thickness of lines or the size of components depicted in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, in the description of the embodiments below, the description of identical or corresponding components may be omitted. However, even if a description of a component is omitted, it is not intended that such component is not included in any embodiment.

[0052] In addition, the following embodiments are not intended to limit the scope of the present invention but are merely exemplary details of the components presented in the claims of the present invention, and embodiments including components that are included in the technical concept throughout the specification of the present invention and are substitutable as equivalents for the components of the claims may be included in the scope of the present invention.

[0053]

[0054] FIG. 1 is a drawing illustrating a metastructure (100) according to an embodiment of the present invention. Referring to FIG. 1, the metastructure according to an embodiment of the present invention is a structure for improving acoustic directivity and includes a tubular structure having a hollow formed inside and a length extended in one direction, wherein the tubular structure may be open toward the internal hollow and a slot (110) may be formed perpendicular to the length direction of the tubular structure.

[0055] According to one embodiment, the slots may be formed in a plurality of ways in the tubular structure having a pattern. Additionally, the plurality of slots may have the same size and length. The slots may function to cause phase interference by changing the phase according to the direction and angle of incidence when sound waves enter the tubular structure.

[0056] According to one embodiment, multiple slots having the same size and length may be formed on the same circumference of the tube. As the slots are formed on the same circumference, sound waves incident from each slot into the interior can structurally maintain a constant phase difference, thereby producing a constant phase interference effect.

[0057] FIG. 2 is a diagram showing the parameters of a metastructure. A may represent the length of the tube structure, B the width of the slot, C the diameter of the tube, and D the spacing between the slots. The spacing between the slots may be 1.1 to 12 times the slot width. The diameter of the tube structure may be 7 to 12 times the slot width.

[0058]

[0059] According to one embodiment, the diameter of the tube structure may be 22.5 mm to 37.5 mm, and the number of slots may be 5 to 50. The spacing between the slots may be 3.5 mm to 34 mm.

[0060]

[0061] FIG. 3 is a side view of an acoustic directivity enhancement system including a metastructure according to an embodiment of the present invention. Referring to FIG. 3, the acoustic directivity enhancement system including a metastructure according to an embodiment of the present invention may include a tubular structure and an acoustic sensor connected to the tubular structure. Additionally, the tubular structure may have a slot formed perpendicular to the longitudinal direction of the tubular structure and open toward an internal hollow. According to an embodiment of the present invention, as illustrated in FIG. 3, not only computations for signal processing and communication of acoustic data but also the execution of physical control commands, including rotational movements of the sensor, can be directly processed at an edge computer. This enables low-latency, high-speed response without communication with a cloud-based server, and offers the advantages of ensuring real-time responsiveness to environmental changes and system independence.

[0062] According to one embodiment, when a sound source is located in the forward direction (0°) of the tubular structure, constructive interference occurs, and sound can be detected by an acoustic sensor. The forward direction may refer to the front of the tubular structure. Conversely, if a sound source is located in a direction other than the forward direction, destructive interference occurs, and sound may not be detected. By utilizing the structural characteristics of such a tubular structure, it is possible to selectively receive only sound incident from a specific direction, thereby effectively improving acoustic directivity.

[0063] According to one embodiment, at least a portion of the acoustic sensor may be inserted into a tubular structure. By inserting at least a portion of the acoustic sensor, acoustic data with improved acoustic directivity can be received more efficiently and accurately. In addition, clearer acoustic data can be obtained while minimizing the influence of external noise. As another example, a portion of the acoustic sensor may be in a form that protrudes outside the tubular structure. In this case, a rotation axis is coupled to the exposed portion of the acoustic sensor, thereby ensuring structural stability during the rotational movement of the acoustic sensor. Furthermore, there is an advantage of increasing the convenience of maintenance.

[0064] According to one embodiment, the acoustic directivity enhancement system may further include a rotation axis connected to the acoustic sensor. The rotation axis may be perpendicular to the longitudinal direction of the tubular structure. The tubular structure may be rotatable 360° around the rotation axis. By rotating, the acoustic sensor can collect acoustic data in all directions with enhanced directivity. Accordingly, acoustic data can be measured more precisely.

[0065] The above-mentioned acoustic data by angle can be classified using a signal processing algorithm. In addition, the location of the sound source can be identified based on the classified acoustic data.

[0066] The above signal processing algorithm calculates the average value of the average sound pressure level (SPL) of acoustic data acquired through a metastructure system in each direction, and can recognize that there is a sound source in a specific direction if there is a peak in that direction.

[0067] A signal processing algorithm according to one embodiment of the present invention can calculate the average value of the sound pressure level (SPL) for each direction by taking acoustic data received from each direction through a metastructure-based acoustic sensor as input. The average value of the sound pressure level is calculated by converting the squared mean of the signals received within a predetermined time interval into a logarithmic scale, and the location of the sound source is determined through comparative analysis of multiple directions. This processing process can be performed in real time on an edge computer.

[0068] In addition, the above signal processing algorithm can determine that a sound source exists in a specific direction if a relatively high peak value is observed in that direction among the calculated average sound pressure levels. This method is performed based on continuous measurement data for multiple directions and has the advantage of effectively identifying the direction of a specific sound source.

[0069] According to one embodiment, the acoustic sensor may comprise a single sensor. This may be because the sensor is rotatably installed, allowing it to collect acoustic data in all directions through the rotation of the sensor itself. Due to this rotatability, unlike conventional array methods that required multiple sensors, the same function can be implemented with only a single sensor, which offers the advantage of enabling the miniaturization of the entire system. Additionally, there is the advantage of easier maintenance due to reduced structural complexity.

[0070] According to one embodiment, the system may be replaceable with another tubular structure designed to have slots of a different pattern from the existing installed tubular structure. The slots of the different pattern may be formed by changing the parameters of the tubular structure. The parameters may be one of the spacing between slots, the number of slots, the diameter of the tubular structure, or the length of the tubular structure. For example, the tubular structure may have a shape in which all frequencies are highly directional toward the front of the tubular structure. For another example, the tubular structure may have different directions of high directionality depending on the frequency. In the embodiments to be described later, the inventors fabricated and tested a first type and a second type of tubular structure. The first type was fabricated with 33 slots, a spacing between slots of 5.23 mm, and a tube diameter of 32.5 mm, while the second type was fabricated with 6 slots, a spacing between slots of 33.52 mm, and a tube diameter of 32.5 mm.

[0071] According to one embodiment, the tubular structure may have a phase cancellation effect in a sound having a frequency of 1873 Hz or higher. Preferably, it may have a phase cancellation effect in a sound having a frequency of 2 kHz or higher and 22 kHz or lower.

[0072]

[0073] A method for enhancing acoustic directivity according to one embodiment of the present invention may include the steps of: rotating an acoustic sensor coupled to a tubular structure having a slot formed therein around a rotation axis perpendicular to the longitudinal axis of the tubular structure; analyzing a specific frequency response received by the acoustic sensor for each rotation angle; and setting the rotation angle at which the frequency response is maximum, corresponding to the specific frequency, as the angle for enhancing directivity. The tubular structure having a slot formed therein may be a metastructure according to one embodiment of the present invention.

[0074] According to one embodiment, an acoustic directivity enhancement system including the metastructure can be utilized as a hardware band filter or a frequency band amplifier. To utilize the system as a hardware bandpass filter, the present invention may further provide an acoustic directivity enhancement method as follows. That is, the acoustic directivity enhancement method may further include the steps of: arranging a tubular structure with a slot formed at the directivity enhancement angle and an acoustic sensor; and destructively interfering with frequencies other than the specific frequency by a phase cancellation mechanism. Through such a phase cancellation mechanism, the system can perform the function of a hardware bandpass filter. Compared to conventional bandpass filter technology, the system has the advantage of being more robust to environmental noise because it is implemented through improvements in the hardware structure without using mathematical calculations or electronic circuits. In addition, it has the advantages of not requiring power consumption or computational resources, being more robust to external environmental noise, and enabling real-time application.

[0075] The above hardware bandpass filter can change its frequency-dependent directivity through changes in the parameters of the metastructure. Accordingly, only sounds of a specific frequency can be acquired. In addition, as the system is rotatable, the target frequency for bandpassing can be changed according to the angle of rotation.

[0076] According to one embodiment, an acoustic directivity enhancement system including the metastructure can be utilized to track the location and direction of a sound source. The sound source may refer to acoustics. To estimate the direction of the sound source, the present invention may further provide an acoustic direction estimation method as follows. That is, the acoustic direction estimation method may further include the step of estimating the location of the sound source using a signal processing algorithm for acoustic data received by the acoustic sensor according to rotation angles.

[0077] The above acoustic data is human speech, and the above signal processing algorithm may be an Automatic Speech Recognition (ASR) algorithm. The above speech recognition algorithm may include a deep learning-based pre-trained speech recognition model. The above speech recognition algorithm may use OpenAI's Whisper model, which is released as open source.

[0078] Accordingly, in work environments where robots and humans coexist or in various indoor and outdoor environments, the user can transmit commands via human voice, and the system can control the robot's operation by analyzing the received acoustic data to recognize the corresponding command. Since acoustic directivity is enhanced by the meta-structure, only signals reinforced from a specific direction among the acoustic data received from all directions can be effectively detected. Consequently, the recognition rate of the command voice can be increased. In addition, the reception accuracy of the command voice can be improved even in environments where ambient noise is present.

[0079]

[0080] Examples

[0081]

[0082] *(Experiment 1) Experiment on Phase Cancellation Effects According to Parameter Changes in Metastructures

[0083] To evaluate the directional performance of an acoustic directional enhancement system comprising a metastructure according to one embodiment of the present invention, the inventors of the present invention conducted an experiment analyzing the directional response by frequency while varying the number of slots, the spacing between slots, and the tube diameter.

[0084] In the experiment, nine tubular structures were used, and for each structure, the directional pattern of a pure-tone sound from 500 Hz to 10 kHz with an intensity of 94 dB SPL (Sound Pressure Level) was recorded at a distance of 2 m. Figure 4 is an experimental graph regarding the phase cancellation effect according to changes in the parameters of the metastructure. Referring to Figure 4, the frequency-dependent directional pattern of each structure can be observed. Based on the above directional pattern, assuming the same tube length, it can be determined that the effect increases as the number of slots increases and the spacing between slots decreases. Furthermore, it can be seen that the most effective directional pattern is obtained when the tube diameter is 32.5 mm.

[0085] An effective directivity pattern may mean that the thickness of the main lobe for each frequency is formed narrowly, which may be due to a phase cancellation effect by a directivity enhancement system including the metastructure.

[0086]

[0087] (Experiment 2) Experiment to Evaluate the Accuracy of Localization of Multiple Sound Sources

[0088] The inventors of the present invention conducted an experiment to evaluate whether the location of various sounds that may occur in daily life can be effectively estimated even in a noisy environment using an acoustic directivity enhancement system according to one embodiment of the present invention.

[0089] In the experiment, the noise levels of factory and crowded environments were increased from 0 dB to 84.5 dB—equivalent to the acoustic sound to be estimated—while tracking the location of the target sound and determining the accuracy. Figure 5 is a diagram representing the experimental data from the above experiment, illustrating an acoustic directivity enhancement system including a metastructure utilizing 3DAR (3-dimensional acoustic ranging) and an acoustic localization system using a signal processing algorithm. More specifically, Figure 5A illustrates a schematic configuration of an acoustic directivity enhancement system designed to estimate the location of sound sources even in noisy environments, such as loud factories or crowded environments, including acoustic sounds that may occur in everyday settings, such as car horns, human voices (e.g., HELP!), ambulance sirens, gas leak sounds, and screams. Figure 5B illustrates a signal analysis process in which the direction of a sound source can be accurately estimated using only a simple algorithm due to the beamforming characteristics of the metastructure. Figure 5C shows the accuracy results of estimating the location of a single acoustic stimulus under various noise conditions. Figure 5D shows the results of the position estimation accuracy of single and multiple acoustic stimuli under various noise conditions.

[0090] Referring to Figure 5, it can be seen that various acoustic locations were estimated with a high accuracy of over 90%.

[0091] It was confirmed that through the system proposed by the inventors, the location of a sound source can be distinguished with an angular resolution of up to approximately 5.831 x 10⁴ degrees (based on a 44.1 kHz sample rate and a 14 s / rev rotation speed) depending on the data acquisition frequency and rotation speed of the microphone. In addition, the inventors confirmed that the location of multiple sound sources can be identified with an accuracy of over 90% even in an environment where the sound pressure of the noise and the sound source are the same.

[0092]

[0093] (Experiment 3) Experiment on tracking the location of multiple human voices for human-robot interaction

[0094] FIG. 6 is experimental data applied to tracking the location of multiple human voices using an acoustic directivity enhancement system including a metastructure according to an embodiment of the present invention. The experiment was conducted in a factory with machine tool and human environmental noise. The location of each person was tracked when three people spoke simultaneously, and referring to FIG. 6, it can be seen that an accuracy of 95.6% or higher was achieved.

[0095] In addition, FIG. 7 is experimental data according to the angle of a human voice using an acoustic directivity enhancement system including a metastructure according to an embodiment of the present invention. Referring to the experimental data in FIG. 7, it can be seen that even if a person does not speak toward the acoustic sensor but speaks toward a direction at an angle of 120°, it shows a position tracking accuracy of 93.8% or higher.

[0096]

[0097] (Experiment 4) Experiment on Change in Direction of Direction According to Frequency

[0098] The inventors of the present invention confirmed through experiments that the directional direction changes according to frequency using an acoustic directivity enhancement system comprising a metastructure according to one embodiment of the present invention.

[0099] In the experiment, a metastructure with 6 slots, a spacing of 33.53 mm between slots, a tube diameter of 32.5 mm, and a tube length of 167.64 mm was used, and a microphone was used as the acoustic sensor. The microphone may be a commercial sensor.

[0100]

[0101] Figure 8 is a diagram showing the experimental directional angle results measured for various frequencies, and Figure 9 is a diagram showing the theoretical directional angle compared with the experimental results of Figure 8.

[0102] Referring to FIGS. 8 and 9, it can be seen that the directional direction changes according to the frequency from 2000 Hz to 10000 Hz from the directional pattern. The directional direction may refer to the direction of the main lobe. Through the experimental results, the inventors of the present invention measured the directional angle from the front of the tube and confirmed that at 2000 Hz it is approximately 71°, at 3000 Hz it is approximately 41°, at 5000 Hz it is approximately 19°, and at 10000 Hz it is approximately 11°.

[0103] The high degree of agreement between these two results confirms that, in actual application, the sound source can be accurately directed to a preset angle without the need for additional correction processes.

[0104]

[0105] (Experiment 5) Hardware Bandpass Experiment

[0106] The inventors of the present invention conducted an experiment to verify whether a directivity enhancement system including a metastructure according to one embodiment of the present invention can function as a hardware bandpass filter.

[0107] In the experiment, a pure tone in the target frequency band was captured with the presence or absence of a metastructure and the presence or absence of 100 dB noise positioned at a 30° angle as variables. Subsequently, the normalized RMS value in the time domain of the captured sound was compared with the peak frequency magnitude processed by FFT (Fourier Transform) in the frequency domain. The target pure tone used was 2000 Hz, and the directivity angle of the system was set to 71°.

[0108]

[0109] FIG. 10 is a diagram showing the comparison results between the metastructure-based acoustic sensor according to the present invention and a sensor without the structure (free-field) condition. Measurements were taken with the metastructure rotated approximately 71° at 2000 Hz, approximately 41° at 3000 Hz, approximately 19° at 5000 Hz, and approximately 11° at 10000 Hz from the front of the tube to orient each frequency.

[0110] More specifically, FIG. 10A is a graph comparing the Root Mean Square (RMS) values ​​of the normalized waveform measured in a noise-free environment and a noise-free environment for a 2 kHz pure-tone sound source, showing a sound reception improvement of 4.03 times in the noise-free environment compared to the free-field condition and 2.59 times in the environment with a 100 dB noise source compared to the free-field condition.

[0111] Figure 10B shows the results of a comparison of normalized FFT (Fast Fourier Transform) peak sizes measured under the same conditions, and the size of the 2000 Hz frequency peak was improved by 4.24 times compared to the free-field condition in a noise-free environment and by 4.82 times compared to the free-field condition in an environment with a 100 dB noise source.

[0112] FIG. 10C is a graph showing the relative waveform RMS values ​​of the structure relative to the free field in clean and noisy environments for pure tone sources of 2, 3, 5, and 10 kHz, and FIG. 10D is the result showing the relative FFT peak size measured under the same frequency conditions as FIG. 10C.

[0113] In addition, FIG. 11 is a table of experimental results in which an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention is applied as a hardware bandpass filter.

[0114] Referring to FIGS. 10 and FIGS. 11, in a noisy environment, a normalized RMS value of 2.59 times and a peak frequency magnitude of 4.82 times were observed for a 2 kHz sound source. This implies that the system of the present invention can be applied as a hardware band filter.

[0115]

[0116] FIGS. 12 to 14 are images of examples in which an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention is applied to a CNC tool failure monitoring hardware bandpass in a noisy factory environment and various experiments are performed.

[0117] Figure 12A is a microscopic image of a normal CNC tool and a worn tool. It shows the experimental setup for a tool failure experiment using face milling sound with the proposed structure on A6061 material in a factory. Figure 12B is a detailed image of the experimental setup, showing the structure collecting sound at an angle of 66.52° targeting normal and failure characteristic frequencies (2041 Hz) in an 84 dB noise environment. Figure 12C shows the experimental results using the structure, based on FFT and Evelope spectrum analysis, indicating that normal CNC tool characteristic frequencies (8f_TPF, f_TPF) were robustly collected even in a noisy environment. Figure 12D shows the experimental results using the structure, based on FFT and Evelope spectrum analysis, indicating that worn CNC tool characteristic frequencies (16f_s, f_s) were robustly collected even in a noisy environment.

[0118] Figure 13A shows the results of comparing the FFT characteristic frequency magnitudes for a normal tool, confirming that the characteristic frequency was improved by approximately 19.4 times in a quiet environment and 9.3 times in a noisy environment, and Figure 13B shows the results of comparing the FFT characteristic frequency magnitudes for a worn tool, confirming that the characteristic frequency was improved by approximately 21.3 times in a quiet environment and 19.9 times in an 81 dB noise environment. In particular, in an 84 dB noise environment, the characteristic frequency could be collected only when the structure was used.

[0119] Figure 14A is an image showing the application of a meta-structure as a hardware bandpass, illustrating the architecture of an AE (autoencoder decoder) model designed to verify the degree of performance improvement of the tool condition diagnosis AI algorithm. Figure 14B shows the results of applying this system. (Left figure) In an 84 dB noise environment, when the structure was not used, all normal tools were recognized as faulty tools (feature frequency not detected), but when the structure was used, approximately 55.7% of the normal tools were accurately recognized. (Middle figure) Also in an 84 dB noise environment, when the structure was not used, all faulty tools were recognized as normal tools (feature frequency not detected), but when the structure was used, approximately 21.8% of the faulty tools were accurately recognized as faulty. (Right figure) In an 81 dB noise environment, when the structure was used, 78.6% of the faulty tools were accurately recognized as faulty. These results demonstrate the hardware band filter performance of the structure, proving that it has a significant impact on improving AI performance.

[0120]

[0121] FIG. 15 is an image of an example in which various experiments were performed by applying a hardware bandpass for Human-Robot interaction and Human-Machine interaction and Human speech recognition to an acoustic directivity enhancement system including a metastructure according to one embodiment of the present invention in a noisy environment.

[0122] FIG. 15A is a diagram of an experiment in which a 76 dB human command is captured through a hardware bandpass filter via a structure in a 94 dB noise environment and then recognized as speech using an ASR (Automatic Speech Recognition) model; FIG. 15B is a detailed photograph of the experimental setup, in which the structure records 76 dB human speech in an 84 dB noise environment and is an image of the structure rotated according to the target frequency (the diagram above is rotated 71 degrees for 2 kHz band amplification / bandpass); FIG. 15C is the waveform and spectrogram of the everyday speech used in the experiment; and FIG. 15D is a graph showing the ASR accuracy when the target frequency is changed and the OpenAI Whisper model of various sizes is changed.

[0123] In the experiments shown in Figs. 15C and 15D, 1) when speech recognition was performed using the largest model (Medium.en) with a target of 2 kHz using the structure in a 94 dB noise environment, the highest accuracy of 88.3% was observed (compared to Free-field), and 2) in a 94 dB noise environment, the speech recognition accuracy of the smaller model (a model with less computational load and parameters) using the structure was higher than the speech recognition accuracy using the large model in Free-field (without the structure). Through this, it was proven that the proposed structure can improve the accuracy of speech recognition, which is essential for HRI and HMI, by applying it as a hardware bandpass filter.

[0124]

[0125] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

[0126]

[0127] <Explanation of Symbols>

[0128] 100: Metastructure

[0129] 200: Acoustic sensor

[0130] 110: Slot

Claims

1. In a structure for improving acoustic directivity, It includes a tubular structure with a hollow formed inside and an elongated length in one direction, The above tubular structure is, Open toward the internal hollow and having a slot formed perpendicular to the longitudinal direction of the tubular structure, Metastructure for enhancing acoustic directivity.

2. In Paragraph 1, The above slots are formed in multiple numbers with a pattern, and The above plurality of slots have the same size and length, Metastructure for enhancing acoustic directivity.

3. In Paragraph 2, The slots having the same size and length are formed in multiple numbers on the same circumference of the tube. Metastructure for enhancing acoustic directivity.

4. In Paragraph 1, The above slot has a length that is 3 to 10 times its width, Metastructure for enhancing acoustic directivity.

5. In Paragraph 1, The diameter of the above tube is 1.5 to 3 times the length of the above slot, Metastructure for enhancing acoustic directivity.

6. In Paragraph 1, The diameter of the above tube is 28 to 36 mm, and The number of the above slots is 25 to 40, and The spacing between the above slots is 3 to 7 mm, Metastructure for enhancing acoustic directivity.

7. Tubular structure; and Acoustic sensor connected to the above tubular structure; including, The above tubular structure is open toward the internal hollow and has a slot formed perpendicular to the longitudinal direction of the tubular structure. Acoustic directivity enhancement system including a metastructure.

8. In Paragraph 7, The above acoustic sensor is at least partially inserted into a tubular structure, Acoustic directivity enhancement system including a metastructure.

9. In Paragraph 7, It further includes a rotating shaft connected to the above acoustic sensor, The above rotation axis is perpendicular to the longitudinal direction of the tubular structure, and The above tubular structure is rotatable 360° around the rotation axis, Acoustic directivity enhancement system including a metastructure.

10. In Paragraph 7, The above acoustic sensor comprises a single sensor. Acoustic directivity enhancement system including a metastructure.

11. In Paragraph 7, The above system is, Replaceable with another tubular structure designed to have a slot pattern different from the existing installed tubular structure, Acoustic directivity enhancement system including a metastructure.

12. In Paragraph 11, The above-mentioned tubular structure is such that a phase cancellation effect occurs in sounds having a frequency of 2 kHz or higher. Acoustic directivity enhancement system including a metastructure.

13. A step of rotating an acoustic sensor coupled to a slotted tubular structure around a rotation axis perpendicular to the longitudinal axis of the tubular structure; A step of analyzing a specific frequency response received by the acoustic sensor according to rotation angle; and A step comprising: setting the rotation angle at which the frequency response is maximum, corresponding to the specific frequency, as the directivity enhancement angle; The above-mentioned tubular structure with the formed slot is the meta-structure of claim 1, Acoustic directivity enhancement and direction estimation method.

14. In Paragraph 13, Step of arranging a tubular structure with a slot formed at the above-mentioned directional enhancement angle and an acoustic sensor; and A step further comprising: a step in which frequencies other than the aforementioned specific frequency are destructively interfered with by a phase cancellation mechanism; Acoustic directivity enhancement and direction estimation method.

15. In Paragraph 13, The method further comprises the step of estimating the location of a sound source using a signal processing algorithm for acoustic data received by the acoustic sensor according to rotation angle. Acoustic directivity enhancement and direction estimation method.

16. In Paragraph 15, The above acoustic data is a human voice, and The above signal processing algorithm is a speech recognition algorithm (ASR). Acoustic directivity enhancement and direction estimation method.

17. In Paragraph 15, The above signal processing algorithm includes a deep learning-based pre-trained speech recognition model, Acoustic directivity enhancement and direction estimation method.

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