Acoustic device

Abstract

Provided is an acoustic device capable of effectively using voice even in noise. The present invention is provided with: a base body part (14) that can be worn by a user and that, when worn by the user, curves with a sound source on an inner side in a worn state; and an electret condenser microphone (20) that has flexibility, is mounted on the base body part (14) with the sound source on the inner side, and is curved so as to follow the shape of the base body part (14). By the curvature of the electret condenser microphone (20), a focal point of sound is formed on the inner side of the electret condenser microphone device (20). A plurality of directional surfaces (46A1 to 46A9) facing the focal point of sound are formed on the electret condenser microphone (20).

Description

sound equipment

[0001] This invention relates to an acoustic device equipped with a microphone or the like.

[0002] In recent years, since the COVID-19 pandemic, opportunities for online meetings have increased. Furthermore, opportunities for meetings and phone calls while on the go have also increased. As a result, many new and high-performance audio devices have become available, such as earphone-type microphones and wearable devices equipped with AI (artificial intelligence) that performs noise cancellation. In addition, with the future development of generative AI, it is expected that devices will be operated interactively. And it is expected that these devices will be used in various situations with a variety of devices such as smartphones, PCs (personal computers), and eyeglass-type devices.

[0003] Prior art related to software is disclosed, for example, in Patent Document 1 and Non-Patent Document 1, listed below. Patent Document 1 proposes a method for acquiring ambient noise and adaptively canceling it (claim 1, etc.). However, the invention disclosed in Patent Document 1 requires the acquisition of ambient noise, making it difficult to respond to instantaneous noise such as sudden loud noises. Furthermore, in the invention disclosed in Patent Document 1, the system performance depends on the ambient noise, so it cannot input quiet sounds in noisy environments (environments with relatively high noise levels, also called "noisy environments").

[0004] Furthermore, Non-Patent Document 1, relating to software, proposes noise processing using deep learning. In the invention disclosed in Non-Patent Document 1, noise is mixed with clean (clear) audio data to create a noisy audio dataset. Then, the learned noise is removed from the created audio dataset, and the audio dataset is converted into clear sound. However, the method in Non-Patent Document 1 is overly optimized for the learned noise, making it difficult to use in situations where multiple people are conversing or when speaking softly in noisy environments, and it cannot be used in extremely noisy environments of around 70-80 dB. In other words, Non-Patent Document 1 discloses a method for reducing noise in real time using deep learning technology. Furthermore, the invention disclosed in Non-Patent Document 1 can only handle specific learned noises. Moreover, it is difficult to use in environments where people are speaking softly or when multiple people are conversing.

[0005] In contrast to the prior art related to this software, for example, Patent Documents 2 to 6, listed below, disclose prior art related to noise-canceling hardware. Patent Document 2 discloses inventions related to contact microphones and throat microphones (claims 1, 6, etc.). Contact microphones and throat microphones are microphones that come into contact with the skin and convert vibrations on the surface of the neck into sound. Because contact microphones and throat microphones can acquire only sound from the surface of the body, they are resistant to external noise. However, because the sound passes through the body's tissues, the voice becomes muffled and difficult to hear. Furthermore, in order to maintain contact between the microphone and the skin, natural (common) movements such as nodding can cause noise.

[0006] Patent Document 3, like Patent Document 2, discloses an invention relating to a contact microphone (claim 1, etc.). In the invention disclosed in Patent Document 3, it is necessary to maintain contact between the microphone and the body, and movements such as head shaking can cause noise.

[0007] Patent document 4 proposes an earphone-type device (claim 1, etc.). The invention disclosed in Patent document 4 uses left and right microphones to identify and filter the wearer's speech. However, it picks up noise emitted from around the wearer's mouth, and even quiet voices such as whispers are picked up as noise. In particular, it is difficult to use in noisy environments of about 70-90 dB.

[0008] Patent documents 5 and 6 propose flexible microphones that use fiber materials.

[0009] Japanese Patent Publication No. 2023-116465, Japanese Patent Publication No. 2017-118481, Japanese Patent Publication No. 2017-112479, U.S. Patent No. 9,576,588, U.S. Patent Application Publication No. 2009 / 0016551, U.S. Patent Application Publication No. 2011 / 0255721

[0010] Alexandre D. et. al, Interspeech, 2020, https: / / arxiv.org / abs / 2006.12847

[0011] By the way, the inventions disclosed in Patent Documents 1 to 6 and Non-Patent Document 1 are not such that they can pick up voices ranging from whispers to loud voices in noisy environments, and that they can be used even in extremely noisy environments of 70 to 90 dB.

[0012] The present invention aims to provide an acoustic device that can effectively utilize sound even amidst noise.

[0013] To achieve the above objective, the present invention provides an acoustic device that can be worn by a user and comprises a base portion that curves inward with the sound source facing inward when worn by the user, and a flexible electret condenser microphone device that is mounted on the base portion with the sound source facing inward and curved to conform to the shape of the base portion. Furthermore, to achieve the above objective, the present invention provides a sound acquisition method that uses an acoustic device comprising a base portion that can be worn by a user and curves inward with the sound source facing inward when worn by the user, and a flexible electret condenser microphone device that is mounted on the base portion with the sound source facing inward and curved to conform to the shape of the base portion, thereby preferentially acquiring the sound of the sound source even in a noisy environment.

[0014] According to the present invention, it is possible to provide an acoustic device that can effectively utilize sound even amidst noise.

[0015] (a) is an explanatory diagram showing a photographic image of a mask-type acoustic device according to an embodiment of the invention, a photographic image of an electret condenser microphone, and a diagram of the configuration of an acoustic system including the electret condenser microphone, and (b) is an explanatory diagram showing a photographic image of the acoustic device being worn by a user. This is an explanatory diagram showing an electrical configuration diagram including an electret condenser microphone and an enlarged view showing the schematic configuration of the electret condenser microphone. (a) is an explanatory diagram showing a schematic diagram showing the state in which the acoustic device is worn on the user's head and a schematic diagram showing the directivity of the electret condenser microphone, (b) is an explanatory diagram showing the partial directivity of the electret condenser microphone, (c) is an explanatory diagram showing the relationship between voice production and noise pickup, and (d) is an explanatory diagram schematically showing the sound propagation related to the electret condenser microphone. (a) and (b) are graphs showing Comparative Example 1. This is a chart showing Comparative Example 2. (a) to (d) are graphs showing Comparative Example 3. This is a chart showing Comparative Example 4. This is an explanatory diagram showing photographic images of the electret condenser microphone samples used in Comparative Example 5, and the measurement results for each sample. This is an explanatory diagram showing photographic images of the face shield type sound device being worn by a user. (a) is an explanatory diagram showing photographic images of the headset type sound device being worn by a user, and (b) is an explanatory diagram showing photographic images of the headset type sound device. (a) is an explanatory diagram showing photographic images of the full-face helmet type sound device being worn by a user, and (b) is an explanatory diagram showing photographic images of the helmet type sound device.

[0016] Figure 1(a) shows a mask (face mask) type acoustic device 10 according to one embodiment of the present invention. The left side of Figure 1(a) shows a photograph of the acoustic device 10, and the upper right side shows a photograph of the microphone equipment (in this case, an electret condenser microphone 20) used in the acoustic device 10. The lower right side of Figure 1(a) also schematically shows the configuration of an acoustic system using the electret condenser microphone 20.

[0017] The sound device 10 is configured by attaching a strip-shaped electret condenser microphone 20 to the inside of a mask portion 12 that has the shape and function of a mask. Various general-purpose masks with flexibility can be used as the mask portion 12. In this embodiment, it comprises a base portion 14 formed by processing nonwoven fabric and two ear loop portions 16 that constitute an annular portion. The base portion 14 is formed by laminating a plurality of nonwoven fabrics and applying predetermined processing.

[0018] As shown in Figure 1(b), the base portion 14 is sized to cover the area from the bridge of the nose to the chin, and from the tip of the nose to the nostrils and cheeks. Furthermore, the upper edge of the base portion 14 contains a core material (not shown) that can be plastically deformed to sandwich the bridge of the nose.

[0019] The ear hook portion 16 is formed from a string-like or strip-like material and is installed between the upper and lower ends on the left and right sides of the base portion 14. By hooking the ear hook portion 16 onto a person's left and right ears, the base portion 14 is pulled to the left and right and deforms to conform to the person's face. Furthermore, by deforming a core material (not shown) from above the base portion 14 so as to sandwich the upper part of the bridge of the nose, the base portion 14 can be made to fit even more snugly against the face.

[0020] Furthermore, the base portion 14 can take on various common forms (for example, a flat form, a pleated form, or a fold-like form). In addition, the base portion 14 can be made from various common materials other than nonwoven fabric (for example, woven fabric or gauze).

[0021] Furthermore, Figure 1(b), mentioned above, is a photographic image showing the mask portion 12 being worn on a human face. In Figure 1(a), a white mask portion 12 is shown, but in Figure 1(b), the mask portion 12 is black. The color of the mask portion 12 may be white, black, or any other color.

[0022] In Figure 1(a), the approximate location of the sound-collecting portion of the electret condenser microphone 20 is indicated by a dashed line. Similarly, in Figure 1(b), the electret condenser microphone 20 is mounted on the inside of the mask portion 12, as indicated by the dashed line. The mask-type acoustic device 10 can be referred to, for example, as a "head-mounted device."

[0023] Next, the electret condenser microphone 20 is designed to deform to conform to the shape of the base portion 14 when the base portion 14 is attached to the face. The electret condenser microphone 20 is constructed by sandwiching a dielectric film portion 24 between a pair of conductive fabric portions 22, as schematically shown in the lower right portion of Figure 1(a) (and the lower portion of Figure 2). A predetermined voltage (for example, a DC voltage of 3.3V) is applied to the conductive fabric portion 22. The thickness of each conductive fabric portion 22 can be, for example, several hundred μm (for example, about 200 μm).

[0024] A polymer film is used for the dielectric film portion 24, and the dielectric film portion 24 functions as a vibrating membrane. The electret condenser microphone 20 charges the dielectric film portion 24, so that static electricity is always generated when a voltage is applied. The electret condenser microphone 20 converts sound (air vibrations) into electrical signals without applying voltage to the dielectric film portion 24 (vibrating membrane). The thickness of the dielectric film portion 24 can be made thinner than the conductive fabric portion 22 (for example, about 10 to tens of micrometers).

[0025] Figure 2 shows an example of an electrical circuit capable of extracting the electrical signal generated by an electret condenser microphone 20. In the example in Figure 2, the electret condenser microphone (EMC unit) 20 is housed in a shield case 28 together with an FET impedance converter 26. The static electricity from the electret condenser microphone 20 is converted into a signal corresponding to the degree of generation by the FET impedance converter 26 and output from the first terminal (Term. 1) 30. The second terminal (Term. 2) 32, which is paired with the first terminal, is grounded. Here, the shield case 28 is not shown in the images or figures of Figure 1(a).

[0026] The conductive fabric portion 22 and dielectric film portion 24 of the electret condenser microphone 20 have enough flexibility to conform to the shape of the base portion 14, as shown in the left-hand diagram in Figure 3(a). Reference numeral 36 in Figure 3(a) indicates a human head, and the ear hooks 16 of the mask portion 12 are placed over the left and right ears 38 of the person. In the example in Figure 3(a), the base portion 14 of the mask portion 12 and the electret condenser microphone 20 are integrally curved to conform to the shape of the human face.

[0027] The characteristics of such an electret condenser microphone 20 can be described, for example, as "shape-following ability" relative to the base portion 14. Experiments by the inventors have shown that by setting the Young's modulus of the conductive cloth portion 22 and the dielectric film portion 24 to, for example, 5 GPa or less, sufficient shape-following ability for constructing a mask-type acoustic device 10 can be obtained. The portion in which the Young's modulus is set to, for example, 5 GPa or less may be at least a part of one of the pair of conductive cloth portions 22, or it may be the entirety. Furthermore, both conductive cloth portions 22 may have such a Young's modulus. In addition, part or the entirety of the dielectric film portion 24 may have such a Young's modulus.

[0028] As shown in the lower right part of FIG. 1(a), the electret condenser microphone 20 is connected to an acoustic chip (Audio Chip) 40, and can be connected to a computer device 42 via the acoustic chip 40.

[0029] In addition, the first terminal 30 and the second terminal 32 shown in FIG. 2 can be incorporated into an electronic circuit portion 43 that connects the electret condenser microphone 20 and the acoustic chip 40. Further, the voltage can be applied to the conductive cloth portion 22 of the electret condenser microphone 20 via the acoustic chip 40 and the electronic circuit portion 43. The wiring of "Signal" (wiring for audio signals) in FIG. 1 corresponds to the wiring 44 connected to the wiring of the first terminal (Term.1) from the power supply of "+Vs" in FIG. 2.

[0030] Also, the communication method between the electret condenser microphone 20 and the computer device 42 (shown in the lower right part of FIG. 1(a)) may be wired communication as shown in FIG. 1(a), or may be wireless communication, which is not shown in the figure. When performing wireless communication, it is conceivable to mount a wireless communication module and a charging battery on the acoustic device 10. In the mask portion 12 of FIG. 1(b), a wireless communication module 45 (including a charging battery) is mounted on the outside.

[0031] Also, the communication method of the wireless communication module may be an analog method or a digital method. Further, for the communication method, various general communication standards such as infrared rays, Wi-Fi, or Bluetooth (registered trademark) can be adopted.

[0032] As shown in the left figure of FIG. 3(a), by bending the electret condenser microphone 20, as shown in the right figure of FIG. 3(a), the directivity is enhanced. That is, due to the bending of the electret condenser microphone 20, a plurality of surfaces facing different directions are formed on the electret condenser microphone 20, as schematically shown in the right figure of FIG. 3(a). For convenience, the surface formed by the bending of the electret condenser microphone 20 is hereinafter referred to as a "directivity surface".

[0033] The directivity surfaces are formed in at least the front direction and the left and right directions of a human. The plurality of directivity surfaces in the curved electret condenser microphone 20 can also be considered to be further subdivided. In the right figure in FIG. 3(a), nine directivity surfaces 46A

[0037] to 46A ９ are subdivided to show the characteristics of the electret condenser microphone 20. Considering a model in which the directivity surfaces of the electret condenser microphone 20 are further subdivided, more smaller directivity surfaces are formed.

[0034] Both the inner surface and the outer surface of the electret condenser microphone 20 constitute directivity surfaces. In the right figure of FIG. 3(a), only the outer directivity surfaces are labeled with reference numerals (46A １ to 46A ９ ), and the illustration of the reference numerals for the inner directivity surfaces is omitted. FIG. 3(b) shows only some of the directivity surfaces (the central directivity surface). Also in FIG. 3(b), only the outer directivity surfaces are labeled with reference numerals (46A ５ ), and the illustration of the reference numerals for the inner directivity surfaces is omitted.

[0035] Each individual directivity surface (here, the inner and outer directivity surfaces including the outer directivity surface 46A １ to 46A ９ ) functions as a planar microphone. In each planar microphone, as shown in FIG. 3(b), sound is mainly collected in a direction perpendicular to the plane. Therefore, in the case of the model shown in the right figure in FIG. 3(a), sound in a direction perpendicular to each of the directivity surfaces 46A １ to 46A ９ (including the inner directivity surfaces) is picked up.

[0036] Also, as shown in FIG. 3(c), consider the case where the sound (voice) B emitted by a human propagates radially from the inside of the mask portion 12 toward the electret condenser microphone 20 while noise C is input from the outside of the mask portion 12. In this case, the human voice B propagates radially outward from the position of the human mouth, which is the focus of the sound.

[0037] Therefore, vocalization B is picked up almost simultaneously across the entire curved surface of the electret condenser microphone 20, which is curved inward in a concave shape. As a result, there is little time difference in the input of vocalization B to the electret condenser microphone 20, and vocalization B can be picked up clearly.

[0038] In contrast, with respect to noise C propagating from the outside, the radially propagating noise C faces the electret condenser microphone 20, which is curved in an outward convex shape. Then, depending on the position of the sound source, the noise C hits a portion of the directional surface of the curved electret condenser microphone 20, and then gradually spreads outward.

[0039] In the example shown in Figure 3(c), noise C is located on the sixth directional surface 46A from the left in the right-hand diagram of Figure 3(a). ６ , and the seventh directional surface 46A ７ It first reaches the area corresponding to the area between the two. Therefore, with respect to the input of noise C to the electret condenser microphone 20, the directivity surface (in this case, the directivity surface 46A) １ ~46A ９ A time difference is likely to occur between each sound. Therefore, noise C is less likely to be picked up compared to vocalization B coming from the inside.

[0040] Furthermore, as shown on the left side of Figure 3(d), a portion of the electret condenser microphone 20 (here, the leftmost directional surface 46A on the right side of Figure 3(a)) １ Let's consider the case where sound is input to the part corresponding to the above. The electret condenser microphone 20 is curved and has multiple directivity surfaces (in this case, the outer directivity surface 46A). １ ~46A ９ Because it is divided into these sections, the propagation of sound (vibration) is obstructed each time at the boundary (or inflection) between adjacent directivity surfaces.

[0041] Therefore, sound (vibration) is effectively attenuated in the electret condenser microphone 20, and sound (vibration) is less likely to propagate throughout the electret condenser microphone 20. In other words, in the electret condenser microphone 20, the sensitivity to the input sound is reduced in areas other than where the sound input occurred (overall sensitivity is suppressed).

[0042] Therefore, the directional surfaces can be selectively utilized, enabling clearer sound capture. And each directional surface (here, the outer directional surface 46A) １ ~46A ９ This provides a highly directional acoustic device 10 that is highly sensitive to sound directly in front of the internal and external directional surfaces (including the internal and external directional surfaces), and less sensitive to sound from any other direction. In the right-hand diagram in Figure 3(a) and the diagram in Figure 3(b), the dotted-dot ellipses drawn to intersect each directional surface schematically represent the directivity of each directional surface.

[0043] Although the electret condenser microphone 20 is a sound-to-electrical converter, it can be applied to a speaker, which is an electrical-to-sound converter. When the curved electret condenser microphone 20 is applied to a speaker, it is possible to output a three-dimensional sound towards the inside of the curved shape (the concave side).

[0044] In this explanation, we conceptually assume that the electret condenser microphone 20 has multiple directional surfaces (internal and external directional surfaces). However, we are not limited to this, and it is also possible to consider the entire continuous curved surface (each of the internal and external curved surfaces) as a single directional surface with sound pickup directivity. Furthermore, multiple directional surfaces as shown on the left side of Figure 3(d) (here, the external directional surface 46A) are also possible. １ ~46A ９ A microphone having internal and external directional surfaces (including the directional surface) can be modeled as an array microphone in which multiple microphones m (directional elements) are arranged in a curved shape (or curved surface), as shown on the right side of Figure 3(d) connected by "≒".

[0045] <Comparative Example 1> Figures 4(a) and 4(b) show the comparative results when speech recognition evaluation was performed on the electret condenser microphone 20. The graph in Figure 4(a) shows the recognition results for normal speech, and the graph in Figure 4(b) shows the recognition results for whispering. Both graphs show the relationship (accuracy) between the sound input to the microphone and the speech signal output from the microphone under a predetermined noise environment (described later) for six different microphone configurations, using bar graphs.

[0046] Four types of noise environments are set. The four types of noise environments are "a30dB", "w40dB", "w60dB", and "w80dB". "a30dB" is without white noise, while "w40dB", "w60dB", and "w80dB" have 40dB of white noise, 60dB of white noise, and 80dB of white noise, respectively.

[0047] The six types of microphone configurations are as follows: (1) First microphone configuration: A configuration using the electret condenser microphone 20 of the embodiment without noise cancellation control. (2) Second microphone configuration: A configuration using the electret condenser microphone 20 of the embodiment with noise cancellation control. (3) Third microphone configuration: A configuration using a conventional contact microphone (pharyngeal microphone in this case) without noise cancellation control. (4) Fourth microphone configuration: A configuration using a conventional contact microphone (pharyngeal microphone in this case) with noise cancellation control. (5) Fifth microphone configuration: A configuration using a conventional earphone type microphone. (6) Sixth microphone configuration: A configuration using a conventional earphone type microphone with noise cancellation control.

[0048] For the noise cancellation control in the second, fourth, and sixth microphone configurations described above, the same control as in Non-Patent Document 1 was performed. For the earphone-type microphones in the fifth and sixth microphone configurations, the same microphones as in Patent Document 4 were used.

[0049] In Figures 4(a) and 4(b), the measurement results for each of the six microphone configurations are grouped together into sets of four (a total of eight sets across the two graphs) for each noise environment. Within each set, the measurement results for the first to sixth microphone configurations are shown in order from left to right. In Figures 4(a) and 4(b), only for "a30dB" the distinction between the first to sixth microphone configurations is indicated by the numbers "1" to "6," but the arrangement order of the measurement results for the first to sixth microphone configurations is the same for "w40dB" to "w80dB."

[0050] Regarding "normal speech" in Figure 4(a), accuracy of nearly 90% was achieved with all microphone configurations at the relatively low noise levels of "a30dB" and "w40dB". In contrast, at the relatively high noise levels of "w60dB" and "w80dB", accuracy decreased in the order of the first to sixth microphone configurations. The superiority of the first microphone configuration (and second microphone configuration) according to this embodiment is more apparent at "w60dB" and "w80dB".

[0051] Furthermore, even when comparing "w60dB" and "w80dB," the superiority of the first microphone configuration (and second microphone configuration) according to this embodiment is more pronounced at "w80dB," which has a relatively higher noise level.

[0052] Regarding the "whispering" in Figure 4(b), the accuracy of the first microphone configuration (and second microphone configuration) according to this embodiment is higher than that of other microphone configurations at "w60dB" and "w80dB". Furthermore, the superiority of the first microphone configuration (and second microphone configuration) according to this embodiment is more pronounced at "w80dB", where the noise level is relatively higher, compared to "w60dB".

[0053] <Comparative Example 2> Figure 5 shows a comparison of characteristics due to differences in microphone structure. Specifically, Figure 5 shows the results of sensitivity measurements performed with different holes (presence or absence), hole size, and hole shape) in the electret condenser microphone 20. In Comparative Example 2, eight types of samples (No. 1 to 8) were prepared and measured. The rightmost column ("Preparation Diagram") in the table of Figure 5 shows images of the experimental setup using each corresponding sample.

[0054] The leftmost column in Figure 5 indicates the item number of the sample. Samples "No. 1" to "No. 3" are "holeless" samples in which the conductive fabric portion 22 and dielectric film portion 24 do not have holes. Note that the measurement results for sample "No. 4" are omitted here because its form overlaps with the other samples.

[0055] Samples "No. 5" and "No. 6" are samples in which relatively small holes (in this case, φ6 mm round holes in the conductive fabric portion 22) are punched in a matrix pattern. The diameter and arrangement of the holes (in this case, round holes) in the conductive fabric portion 22 in samples "No. 5" and "No. 6" are the same. However, as shown in the "Film PFA" column, the presence or absence of holes in the dielectric film portion 24 differs from one another. Here, "PFA" is the material (perfluoroalkoxyalkane) of the dielectric film portion 24 used in this comparative example.

[0056] The dielectric film portion 24 in "No. 5" is "holeless," meaning it does not have holes. The dielectric film portion 24 in "No. 6" is "perforated," meaning it has holes. The holes in the dielectric film portion 24 in "No. 6" are arranged concentrically with the holes in the conductive fabric portion 22 to which it is combined. The size of the holes in the dielectric film portion 24 is smaller than the holes in the conductive fabric portion 22 to which it is combined (φ6 mm) (in this case, φ4 mm).

[0057] Samples "No. 7" and "No. 8" are samples in which relatively large holes (in this case, φ10 mm round holes in the conductive fabric portion 22) are punched in a matrix pattern. The diameter and arrangement of the holes (in this case, round holes) in the conductive fabric portion 22 of samples "No. 7" and "No. 8" are the same. However, as shown in the "Film PFA" column, the presence or absence of holes in the dielectric film portion 24 differs from one another.

[0058] The dielectric film portion 24 in "No. 7" is "holeless," meaning it does not have holes. The dielectric film portion 24 in "No. 8" is "perforated," meaning it has holes. The holes in the dielectric film portion 24 in "No. 8" are arranged concentrically with the holes in the conductive fabric portion 22 to which it is combined. The size of the holes in the dielectric film portion 24 is smaller than the holes in the conductive fabric portion 22 to which it is combined (φ10 mm) (in this case, φ8 mm). Also, the diameter of the holes in the dielectric film portion 24 in "No. 8" (in this case, φ8 mm) is larger than the diameter of the holes in the dielectric film portion 24 in "No. 6" (in this case, φ4 mm).

[0059] In Figure 5, "adhesion" indicates the molded form of the adhesive material that joins the conductive fabric portion 22 and the dielectric film portion 24. As the adhesive, a sheet-like double-sided adhesive material was used, molded into various shapes using a cutter knife or the like. In sample "No. 1", the adhesive material is molded into a rectangular frame shape so that it is placed only on the outer periphery (outer edge) of each conductive fabric portion 22 and dielectric film portion 24. In sample "No. 2", the adhesive material is molded into a relatively coarse grid pattern (a grid pattern with a large grid size, a mesh pattern with a large mesh size, and so on).

[0060] In sample "No. 3," the adhesive is molded into a finer (denser) grid compared to "No. 2." In samples "No. 5" through "No. 8," the adhesive is molded into a relatively coarser grid, similar to sample "No. 2."

[0061] The "Diagram" column shows the difference in loudness (difference in how it sounds) when the sounds captured by samples "No. 1" to "No. 8" are output from a common speaker. The loudness was obtained by the same evaluator subjectively (emotionally). The louder the sound, the better the sound capture effect and the better the microphone.

[0062] The sound levels for samples "No. 1" through "No. 8" were "5," "5," "4," "8," "7," "6.5," and "5," respectively. Sample "No. 5" received the highest score of "8." In other words, the measurement results obtained from sample "No. 5," which had relatively small holes in the conductive fabric portion 22, a coarse adhesive grid, and no holes in the dielectric film portion 24, were the best.

[0063] <Comparative Example 3> Figures 6(a) to (d) show the measurement results of the directivity of the electret condenser microphone 20. Figures 6(a) to (d) show the measurement results for sounds at 500 Hz, 1000 Hz, 5000 Hz, and 10000 Hz, respectively. 0°, 90°, 180°, and 270° in each figure correspond to the front, right, back, and left of the electret condenser microphone 20, respectively.

[0064] On the left side of Figure 6, the measurement method in Comparative Example 3 is schematically shown, separate from Figures 6(a) to (d). The measurement is performed by capturing a sound of a predetermined magnitude (80 dB in this case) output from a speaker using seven electret condenser microphones 20 (Nos. 1-3, Nos. 5-8), similar to those used in Comparative Example 2. The electret condenser microphones 20 (Nos. 1-3, Nos. 5-8) are rotated as shown by the dashed lines. The rotation of the electret condenser microphones 20 (Nos. 1-3, Nos. 5-8) is performed in 30° increments from 0 to 360°. The axis of each angle represents the sound magnitude (in dB), and the sound becomes louder as you move towards the outside of the figure (outside in the radial direction).

[0065] The eight charts in Figures 6(a) to 6(d) represent the measurement results for each electret condenser microphone 20 (No. 1 to 3, No. 5 to 8) of each structure. "mic2-1" to "mic2-3" and "mic2-5" to "mic2-8" in each graph represent the seven electret condenser microphones 20 (No. 1 to 3, No. 5 to 8). The numbers at the end of "mic2-1" to "mic2-3" and "mic2-5" to "mic2-8" correspond to the numbers "1" to "3" and "5" to "8" in the item numbers "No. 1" to "No. 3" and "No. 5" to "No. 8" of the seven electret condenser microphones 20.

[0066] The measurement results in Figures 6(a) to 6(d) show that, generally speaking, "mic2-1" to "mic2-3" and "mic2-5" to "mic2-8" exhibit strong (sharp) directivity in the front-to-back direction (0° and 180° directions) and weak (dull) directivity in the left-to-right direction (90° and 270° directions). In the graph for 500 Hz in Figure 6(a) and the graph for 1000 Hz in Figure 6(b), the chart for "mic2-1" (No. 1) clearly shows the directivity trend.

[0067] "mic2-1" (No. 1) is an electret condenser microphone 20 without holes in the conductive cloth portion 22 and dielectric film portion 24, as shown with reference to Figure 5. In addition, in "mic2-1" (No. 1), the adhesive material is placed only on the outer circumference, and the sound level (subjective score) indicated in the "Drawing Diagram" column is "5".

[0068] In the graph for 5000 Hz in Figure 6(c) and the graph for 10000 Hz in Figure 6(d), the chart for "mic2-5" (No. 5) clearly shows a directional tendency.

[0069] "mic2-5" (No. 5) is an electret condenser microphone 20 in which small holes (φ6 mm) are made in the conductive cloth portion 22, and no holes are made in the dielectric film portion 24, as shown with reference to Figure 5. In addition, in "mic2-5" (No. 5), the adhesive material is arranged in a coarse grid pattern, and the sound level (subjective score) indicated in the "Drawing Diagram" column is "8".

[0070] <Comparative Example 4> Figure 7 shows the measurement method and measurement results for Comparative Example 4. In Comparative Example 4, the impulse response related to vocalization and the impulse response related to noise are measured. As shown on the left side of Figure 7, the measurement is performed by attaching a voice simulator to a dummy head (mannequin head) 50. The voice simulator consists of an experimental acoustic device 10 (WhisperMask) attached to the dummy head 50, a neck speaker 54, and a computer device 42 that uses the reference to Figure 1(a).

[0071] As shown on the left side of Figure 7, the measurement of vocalization is performed by outputting a sound of a predetermined magnitude (in this case, over 80 dB) from the neck speaker 54 and collecting it with the electret condenser microphone 20 of the sound device 10. The magnitude of the sound output from the neck speaker 54 is adjusted so that the magnitude of the sound reaching the electret condenser microphone 20 is 80 dB.

[0072] Noise measurements are performed by placing a noise speaker 56 in front of the dummy head 50. The distance between the acoustic device 10 of the dummy head 50 and the noise speaker 56 is 500 mm in this measurement. The noise speaker 56 emits a sound (noise) of a predetermined magnitude (60 dB, 80 dB in this case), and the sound emitted from the noise speaker 56 is input to the electret condenser microphone 20 of the acoustic device 10.

[0073] The white text "20cm × 2cm" at the bottom left of Figure 7 represents the dimensions (length × width) of the electret condenser microphone 20 used in this measurement.

[0074] In this measurement, the waveform of the vocalization (the waveform of the sound output from the neck speaker 54) and the waveform of the noise (the waveform of the sound output from the noise speaker 56) are the same. In other words, although the magnitude of the vocalization waveform and the waveform of the 60 dB noise and the waveform of the 80 dB noise differ, the shape of the waveforms is the same.

[0075] The graph in Figure 7 shows the waveforms of the measurement results (impulse response) for each sound superimposed. Curve D in the figure shows the measurement results related to vocalization (sound from the neck speaker 54 of the dummy head 50). Curve E in the figure shows the measurement results related to 60 dB noise, and curve F shows the measurement results related to 80 dB noise. The horizontal axis of the graph represents frequency, and the vertical axis y represents amplitude. The unit of the horizontal axis is [Hz], and the unit of the vertical axis is [dB].

[0076] As shown in the graph in Figure 7, the waveform of vocalization (curve D) shows a clearly larger amplitude in the 200-4000 Hz range, which is included in the frequency band of the human voice, compared to the noise (here, 60 dB (curve E), 80 dB (curve F)). The shaded area in the graph represents the difference between the waveform of vocalization (curve D) and the waveform related to the relatively large noise (80 dB) (curve F). From these findings, it can be seen that the voice is captured more clearly than the large noise (80 dB, curve F). Furthermore, it can be seen that the vocalization from the human mouth (located inside), which is the focal point of the sound during capture, is input more strongly than the external noise.

[0077] <Comparative Example 5> Figure 8 shows the measurement method and measurement results related to Comparative Example 5. Comparative Example 5 shows the impulse response of three types of electret condenser microphones 20 with different structures.

[0078] The upper photographic images in Figure 8 show samples related to the electret condenser microphone 20. The area of ​​each sample is 900 mm². ２The dimensions are (30 mm x 30 mm). The leftmost sample has no holes. In the central sample, only the conductive fabric portion 22 has holes (in this case, 9 (3 x 3) circular holes), and in the rightmost sample, holes (in this case, 9 (3 x 3) circular holes) penetrate both the conductive fabric portion 22 and the dielectric film portion 24. Hereafter, these samples may be referred to as "no holes," "holes in fabric only," and "holes in both fabric and film."

[0079] The three graphs (a) to (c) in the lower section of Figure 8 show the measurement results for the samples in the upper section (from left to right: "no holes," "holes in cloth only," and "holes in cloth and film"). Each graph shows multiple waveforms, which are measurement results obtained by changing the angle (measurement angle) relative to the sound source. The measurement angle is in 30° increments from 0° to 330°. 0°, 90°, 180°, and 270° correspond to the front, right, back, and left sides of the electret condenser microphone 20, respectively.

[0080] The horizontal axis of each graph represents frequency, and the vertical axis represents amplitude. The unit of the horizontal axis is [Hz], and the unit of the vertical axis is [dB].

[0081] As shown in the three graphs at the bottom of Figure 8, the same characteristics as when no holes are made are obtained even when 20 holes are drilled in the electret condenser microphone. In addition, in all graphs, there is variation in the amplitude of each waveform at frequencies from 400 to 10000 Hz, but amplitudes of approximately 20 to 40 dB are obtained for angles other than 90° (right) and 270° (left). Furthermore, if we were to compare "no holes," "holes in cloth only," and "holes in cloth and film," the amplitude of the waveforms at 0° and 180° in the "holes in cloth only" sample reaches over 40 dB in the frequency band of 2000 to 5000 Hz, which is larger than that of the other samples.

[0082] <Summary of each comparative example> From the above comparative examples, the following can be said in general: (a) The directivity is sharp (strong) in the 0° (front) direction and 180° (back) direction at all frequencies. (b) Speech from the mouth (inside the electret condenser microphone 20) is input to the electret condenser microphone 20 at a greater rate than noise from the outside. (c) The structure of the electret condenser microphone 20 can be made to have a hole, or the same characteristics can be obtained as when there is no hole. (d) The same characteristics can be obtained even if the size of the hole is changed. (f) By bending the electret condenser microphone 20 and directing it towards the object to be picked up (such as the mouth), the sound of a specific object can be preferentially acquired even in a noisy environment.

[0083] As described above, the acoustic device 10 using the electret condenser microphone 20 according to the embodiment and comparative example makes it possible to pick up not only normal voices but also quiet voices such as whispers in noisy environments of about 70 to 80 dB, where selective sound pickup was difficult with conventional microphones. Furthermore, it eliminates the need to raise one's voice even in noisy environments. As a result, it becomes possible to provide an acoustic device 10 that can effectively utilize voice even in noisy environments.

[0084] Such electret condenser microphones 20 and sound devices 10 can be curved, for example, to make only the wearer's voice usable even in noisy environments. Furthermore, bending the electret condenser microphone 20 (and sound device 10) increases its directivity, making it possible to dominantly (selectively) input sounds from the inside.

[0085] Furthermore, as shown on the left side of Figure 3(d), the sound device 10 reduces sensitivity by ensuring a large area for the electret condenser microphone 20, making it possible to preferentially input sounds that are close to the electret condenser microphone 20. From this, it can be seen that the electret condenser microphone 20 and the sound device 10 can selectively input only the voice of the person wearing the sound device 10, even in a noisy environment. Regarding the area of ​​the electret condenser microphone 20, ensuring a larger area increases its flexibility, making it more difficult for sound to propagate (and thus reducing overall sensitivity).

[0086] Although comparative examples are omitted here, in the inventors' experiments, similar results were obtained when the size of the electret condenser microphone 20 was changed to "20 cm x 4 cm" and "10 cm x 2 cm" in addition to "20 cm x 2 cm," and measurements were performed in the same manner as in <Comparative Example 1>, <Comparative Example 3>, and <Comparative Example 4>.

[0087] <Second Embodiment> The electret condenser microphone 20 can be combined with existing or new head-mounted devices if it can be used in a curved state. In the example in Figure 9, a face shield type acoustic device 60 (second embodiment) is shown in which the electret condenser microphone 20 is mounted inside a transparent face shield portion 62. The electret condenser microphone 20 has a size close to a perfect square, rather than a strip-shaped size (length x width) as in the first embodiment.

[0088] In this way, by reducing the size of the electret condenser microphone 20, the electret condenser microphone 20 can be made less conspicuous. Furthermore, the visibility of the transparent face shield portion 62 from the outside can be prevented as much as possible from being obstructed by the electret condenser microphone 20.

[0089] The face shield portion 62 is curved in a convex shape with its central part in the left-right direction. The electret condenser microphone 20 is also curved to follow the inner shape of the face shield portion 62. The sound device 60 is also equipped with a wireless communication module 45 (including a rechargeable battery).

[0090] <Third Embodiment> In the examples shown in Figures 10(a) and 10(b), a headset-type acoustic device 70 (third embodiment) is shown, in which an electret condenser microphone 20 is mounted inside the headset portion 72. The electret condenser microphone 20 according to the third embodiment is formed in a strip shape, similar to the first embodiment. However, it is not limited to this, and may be formed in a shape other than a strip, for example, a square shape in the second embodiment.

[0091] The microphone boom 74 of the headset unit 72 extends in the left-right direction and is curved in an outward-convex shape. The electret condenser microphone 20 is also curved to follow the inner shape of the microphone boom 74. This sound device 70 is also equipped with a wireless communication module 45 (including a rechargeable battery).

[0092] <Fourth Embodiment> In the examples shown in Figures 11(a) and 11(b), a full-face helmet type acoustic device 80 (fourth embodiment) is shown, in which an electret condenser microphone 20 is mounted inside the full-face helmet portion 82. The electret condenser microphone 20 according to the fourth embodiment is formed in a strip shape, similar to the first embodiment. However, it is not limited to this, and may be formed in a shape other than a strip, for example, a square shape in the second embodiment.

[0093] The chin guard portion 84 of the headset portion 72 is curved in a convex shape with the central part in the left-right direction convex outwards. The electret condenser microphone 20 is also curved along the inner shape of the chin guard portion 84, as shown by the dashed line in Figure 11(b). This sound device 80 is also equipped with a wireless communication module (including a rechargeable battery), but the wireless communication module is not shown in Figures 11(a) and (b).

[0094] <Other Embodiments> The acoustic device is not limited to those described above, and can be formed into various types of head-mounted devices. For example, head-mounted devices such as eyeglasses, sports face guards, etc., can also be configured as acoustic devices.

[0095] <Inventions that can be extracted from embodiments and comparative examples> (1) An acoustic device (acoustic device 10, 60, 70, 80, etc.) comprising: a base portion (such as the base portion 14 of the mask portion 12) that can be worn by a user and, when worn by the user, curves inward with the sound source (such as a human mouth) facing inward; and an electret condenser microphone device (such as the electret condenser microphone 20) that is flexible, is attached to the base portion with the sound source facing inward, and is curved to conform to the shape of the base portion. (2) The acoustic device according to (1) above, wherein the curvature of the electret condenser microphone device forms a sound focal point (such as a point that coincides with the position of the sound source) inside the electret condenser microphone device. (3) The electret condenser microphone device has a plurality of directional surfaces (outer directional surface 46A) facing the sound focal point. １ ~46A ９(1) above, an acoustic device that forms an inner directional surface, etc. (4) An acoustic device that preferentially acquires sound from a sound source even in a noisy environment. (5) An acoustic device that comprises an electret condenser microphone device comprising a pair of electrode portions (conductive cloth portion 22, etc.) having at least a portion of which has a Young's modulus of 5 GPa or less, and a dielectric portion (dielectric film portion 24, etc.) interposed between the electrode portions. (6) An acoustic device (acoustic device 10, etc.) according to any one of (1) to (5) above, which is a mask type that covers at least a portion of the user's face. (7) An acoustic device (acoustic device 60, etc.) according to any one of (1) to (5) above, which is a headset type that is worn on the user's head. (8) An acoustic device (acoustic device 70, etc.) according to any one of (1) to (5) above, which is a full-face helmet type that is worn on the user's head. (9) An acoustic device (such as the acoustic device 80) described in any one of the above items (1) to (5), which is a neck speaker type that is attached to the neck of the user. (10) An acoustic device (such as the acoustic device 10, 60, 70, 80) that can be attached to a user and, when attached to the user, curves inward with the sound source (such as a human mouth) facing inward, and an electret condenser microphone device (such as the electret condenser microphone 20) that is flexible, attached to the base with the sound source facing inward, and curved to conform to the shape of the base, wherein the acoustic device (such as the acoustic device 10, 60, 70, 80) is used to preferentially acquire the sound of the sound source even in a noisy environment. (11) The acoustic device (such as the acoustic device 10) described in the above item (10), wherein the curve of the electret condenser microphone device forms a sound focus inside the electret condenser microphone device to acquire the sound of the sound source.

[0096] <<<Details of this embodiment>>> As described above, the present invention has been described by this embodiment, but the descriptions and drawings that form part of this disclosure should not be understood as limiting the invention. Thus, the present invention naturally includes various embodiments and the like that are not described herein. Cross-reference of related applications

[0097] This application claims priority over Japanese Patent Application No. 2025-024701, filed with the Japan Patent Office on 19 February 2025, all of which disclosures are incorporated herein by reference in their entirety.

[0098] 10, 60, 70, 80: Acoustic device 12: Mask part 14: Base part 16: Ear hook part 20: Electret condenser microphone 22: Conductive fabric part 24: Dielectric film part 38: Ear 45: Wireless communication module 46A １ ~46A ９ : Outer directional surface 60: Acoustic device 62: Face shield section

Claims

1. An acoustic device comprising: a base portion that can be attached to a user and, when attached to the user, curves with the sound source facing inward; and a flexible electret condenser microphone device that is attached to the base portion with the sound source facing inward and curved to conform to the shape of the base portion.

2. The acoustic device according to claim 1, wherein the curvature of the electret condenser microphone device forms a sound focus inside the electret condenser microphone device.

3. The acoustic device according to claim 1, wherein the electret condenser microphone device has a plurality of directional surfaces that are directed toward the focus of the sound.

4. The sound device according to claim 2, which preferentially acquires sound from the sound source even in a noisy environment.

5. The acoustic device according to claim 4, wherein the electret condenser microphone device comprises a pair of electrode portions, at least a portion of which has a Young's modulus of 5 GPa or less, and a dielectric portion interposed between the electrode portions.

6. The acoustic device according to any one of claims 1 to 5, wherein it is a mask type that covers at least a portion of the user's face.

7. The acoustic device according to any one of claims 1 to 5, which is a headset type worn on the user's head.

8. The acoustic device according to any one of claims 1 to 5, wherein it is a full-face helmet type that is worn on the user's head.

9. The acoustic device according to any one of claims 1 to 5, wherein it is a neck speaker type that is worn on the user's neck.

10. A sound acquisition method that uses an acoustic device comprising: a base portion that can be attached to a user and, when attached to the user, curves with the sound source facing inward; and a flexible electret condenser microphone device that is attached to the base portion with the sound source facing inward and curved to conform to the shape of the base portion, thereby preferentially acquiring the sound of the sound source even in a noisy environment.

11. The sound acquisition method according to claim 10, wherein the curvature of the electret condenser microphone device forms a sound focus inside the electret condenser microphone device to acquire the sound of the sound source.

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