Audio devices

Abstract

The present invention provides an acoustic device that suppresses the decrease in sound pressure near a predetermined frequency. [Solution] The sound device comprises a substrate equipped with a circuit for generating a drive signal, an acoustic output element for generating sound waves in accordance with the drive signal, an acoustic film connected to the acoustic output element for diffusing the sound waves, and a housing that houses the substrate, the sound device, and the acoustic film inside, wherein the substrate is provided so as to divide the space inside the housing into an upper cavity and a lower cavity, the upper cavity and the lower cavity are in communication through an opening, and the opening includes a substrate opening that penetrates the substrate.

Description

Technical Field

[0001] The present disclosure relates to an acoustic device, and more particularly to an acoustic device used for outputting an alarm sound in an in-vehicle device.

Background Art

[0002] In recent years, in-vehicle devices have been considering acoustic devices that generate alarm sounds for theft prevention and safety improvement. In an acoustic device, frequency characteristics and sound pressure are elements that determine acoustic performance. The audible frequency range that humans can hear is from 20 Hz to 20,000 Hz (20 kHz), and the frequency of the sound of existing alarm alarms is set in the range of 2 kHz to 4 kHz. This is because the human ear has high sensitivity in the range of 2 kHz to 4 kHz and it is easy to hear the sound. Therefore, the alarm alarm is designed so that the sound pressure becomes large so that the sound reaches far in this frequency band.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In existing acoustic devices, when outputting an alarm sound in the frequency band of 2 kHz to 4 kHz, the sound pressure may decrease near a predetermined frequency. For this reason, the sound in that frequency band becomes weak, and for example, in an environment with a lot of noise, the alarm sound may be difficult to recognize. In addition, since non-uniformity occurs in the frequency characteristics, the sound may be felt intermittently, and it may be difficult to convey the urgency of the alarm sound to the listener.

[0005] Non-limiting embodiments of the present disclosure contribute to providing an acoustic device that suppresses a decrease in sound pressure near a predetermined frequency. [Means for solving the problem]

[0006] An acoustic device according to one embodiment of the present disclosure comprises a substrate equipped with a circuit for generating a drive signal for generating sound waves, and a housing that houses the substrate inside, wherein the substrate is provided so as to divide the space inside the housing into an upper cavity and a lower cavity, the upper cavity and the lower cavity are in communication through an opening, and the opening includes a substrate opening that penetrates the substrate. [Effects of the Invention]

[0007] According to this disclosure, it is possible to suppress the decrease in sound pressure near a predetermined frequency. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of an acoustic device according to Embodiment 1, and is a cross-sectional view along the B-B' section in Figure 2. [Figure 2] Figure 2 is a cross-sectional view along the A-A' section in Figure 1. [Figure 3A] Figure 3A is a conceptual diagram of the gap between the housing and the substrate and the opening in the substrate. [Figure 3B] Figure 3B is a conceptual diagram of the gap between the housing and the circuit board, and the opening in the circuit board. [Figure 4] Figure 4 is a diagram illustrating the aperture area ratio. [Figure 5] This graph shows the dependence of the sound pressure improvement rate around 3.0 kHz on the aperture area ratio. [Figure 6] This graph shows the dependence of the sound pressure improvement rate of the maximum sound pressure on the aperture area ratio. [Figure 7] This graph shows the dependence of the sound pressure improvement rate of the maximum sound pressure on the aperture area ratio during sweep control from 2.6kHz to 3.5kHz. [Figure 8] This graph shows the sound pressure around 3.0 kHz. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described in detail below, with reference to the drawings as appropriate. However, some unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters and redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0010] The attached drawings and the following description are provided to enable a person skilled in the art to fully understand this disclosure, and are not intended to limit the subject matter described in the claims.

[0011] The sound device 1 according to this embodiment can be used, for example, as a self-powered siren. A self-powered siren is a type of siren used in vehicle security systems and can be activated when an abnormality is detected inside the vehicle. Because this siren can operate on its own power without relying on an external power source, it can emit an alarm even if the vehicle's battery is dead. It can also work in conjunction with other sensors such as intrusion sensors and tilt sensors to detect intrusion into the vehicle or theft of tires, and deter intruders with a powerful sound. The sound device 1 can be used not only as a self-powered siren, but also as a siren for security systems in various places such as homes, offices and shops, commercial facilities and public facilities.

[0012] Figure 1 is a cross-sectional view of an acoustic device according to Embodiment 1. Figure 2 is a cross-sectional view along the A-A' section in Figure 1. As shown in these figures, the acoustic device 1 comprises a substrate 3, an acoustic output element 5, an acoustic film 4, a battery 6, and a housing 2 that houses these components.

[0013] (Enclosure 2) As shown in Figures 1 and 2, the acoustic device 1 has a housing 2 that provides space for housing the circuit board 3 and space for housing the battery 6. The housing 2 consists of an upper housing 21 and a lower housing 22, and is a component that protects the components and circuit board housed inside and isolates them from the influence of the external environment. The housing 2 is designed with mechanical strength and environmental resistance in mind, and is configured to protect the internal electronic components from external vibrations, shocks, humidity, dust, etc. The housing 2 also provides internal space or cavities to improve the efficiency of component placement and wiring.

[0014] The housing 2 can be made of a resin or metal that offers excellent durability, heat resistance, and lightweight properties. For example, the housing 2 is made of polybutylene terephthalate (PBT) resin. PBT resin has excellent impact resistance, heat resistance, and chemical resistance, and also achieves high mechanical strength. By using this material, the housing 2 is highly durable against the influence of the external environment and provides stable performance over a long period of time.

[0015] The housing 2 may be equipped with a connector for electrical connection to an external power source such as an onboard battery. The housing 2 may also be equipped with a connector for receiving siren activation and deactivation commands.

[0016] As shown in FIG. 2, on the upper surface of the upper housing 21 of the housing 2, a ring-shaped opening for radiating sound waves to the outside is provided. The inner surface of the ring-shaped opening has an increasing inner diameter upward. Also, inside the opening, a substantially conical recessed member with an increasing inner diameter upward is provided. A ring-shaped slit for providing a path through which sound waves pass is provided between the substantially conical recessed member and the substantially conical inner surface of the upper housing 21. By arranging the substantially conical slit with an increasing outer shape and inner diameter upward, the radiation direction of the sound waves to the outside spreads, and the sound waves can be diffused over a wide range. The radiation direction of the sound waves can be controlled by the width, angle, and shape of the slit, and it is possible to concentrate the sound in a specific direction or disperse the sound over a wide range. The ring-shaped slit may be divided into a plurality of regions. Note that the opening for radiating sound waves to the outside is not limited to a ring shape. The opening for radiating sound waves to the outside may be, for example, a horn-type or bell-type opening like the widened portion at the tip of a trumpet, a porous structure in which a large number of small holes are provided on the surface of the case to disperse the sound waves in a plurality of directions and diffuse them to the outside, a grill structure in which a grill-shaped opening is provided in the case so that the sound waves spread evenly to the outside, or a duct structure in which an acoustic duct is provided inside the case.

[0017] A structure for supporting the outer edge portion of the acoustic film 4 may be provided on the inner surface of the upper housing 21 of the housing 2. For example, on the inner surface of the upper housing 21, a support rib for supporting the outer edge portion of the acoustic film 4, a clamp structure for sandwiching the acoustic film 4, a flange for adhering the acoustic film 4, or a snap-fit structure for making the acoustic film 4 detachable may be provided.

[0018] As shown in FIG. 2, the lower housing 22 of the housing 2 includes a bottom portion, a side portion, and a flange portion extending in the outer peripheral direction from the side surface. The height of the edge of the side portion is higher than that of the flange portion that contacts the end of the side portion of the upper housing 21. By increasing the height of the edge, the adhesion with the upper housing 21 is improved, and the strength, assembly accuracy, and sealing performance can be enhanced.

[0019] The connection between the upper housing 21 and the lower housing 22 may be made by a snap-fit structure in which a plurality of protrusions (snaps) are provided on one of the upper housing 21 and the lower housing 22, and a recess (fit) is provided on the other. Also, screw holes may be provided in the upper housing 21 and the lower housing 22 and fixed with screws. Further, in order to ensure airtightness, the upper housing 21 and the lower housing 22 may be joined using an adhesive.

[0020] (Substrate 3) The substrate 3 is a substrate for physically supporting and electrically connecting electronic components. The substrate 3 is, for example, a single-sided substrate having a wiring pattern on one side and components mounted on the other side, a double-sided substrate having wiring patterns on both sides of the substrate and capable of connecting the front and back wirings with through holes, or a multilayer substrate having a plurality of wiring layers. Pads and through holes (however, not penetrating the substrate 3) for fixing and connecting electronic components may be arranged on the substrate 3. Examples of electronic components include a drive circuit for driving a piezoelectric buzzer, a control circuit for controlling the drive circuit, and a switch for switching from an external power source to an internal battery. The substrate 3 may be supplied from an external power source via a connector provided in the housing 2, or may be supplied from an internal battery 6 housed inside the acoustic device 1, or the external power source and the internal power source may be configured to be switchable.

[0021] In order to connect the housing 2 and the substrate 3, the housing 2 is provided with a structure for physically and stably fixing the substrate 3. This connection structure securely holds the substrate 3 inside the housing and provides means for appropriately making an electrical connection with the outside of the housing.

[0022] Inside the lower housing 22, a plurality of fixing protrusions for supporting the substrate 3 may be provided. These plurality of fixing protrusions are provided at predetermined positions of the substrate 3 and are arranged to coincide with the mounting holes of the substrate 3. The substrate 3 is fixed in a state of being fitted into these protrusions, and the substrate 3 is held inside the housing by, for example, a retainer or a snap-fit structure provided on the protrusions.

[0023] Note that the substrate opening 33 provided in the substrate 3 is not shown in Figures 1 and 2. The substrate opening 33 will be explained later using Figures 3 and 4.

[0024] (Acoustic output element 5) The acoustic output element 5 is, for example, a piezoelectric buzzer. A piezoelectric buzzer consists of a piezoelectric element and a diaphragm, and these elements work together to generate sound waves. The piezoelectric element uses the piezoelectric effect to convert electrical energy from a power source into mechanical vibrations. The piezoelectric element is placed on the diaphragm, sandwiching it from above and below. The diaphragm and the piezoelectric element each have a roughly circular shape with their centers coaxially aligned, and the diameter of the diaphragm is larger than the diameter of the piezoelectric element. When a driving voltage is applied to the piezoelectric element, an electric field is generated within the piezoelectric element, and due to the piezoelectric effect, the piezoelectric element itself deforms in response to the electric field, repeatedly performing minute expansion and contraction movements. This expansion and contraction movement becomes a mechanical vibration, and this vibration is transmitted to the diaphragm. When the diaphragm vibrates, it pushes and pulls the surrounding air, creating fluctuations in air pressure. These fluctuations in air pressure become the source of sound waves. The sound waves then propagate through the surrounding air and spread out as pressure waves.

[0025] The substrate 3 is provided with a drive circuit for controlling the piezoelectric element and wiring for sending a drive signal to the piezoelectric element. The drive signal is sent to the piezoelectric element via the drive circuit. The drive circuit controls the piezoelectric element to operate at an appropriate frequency and amplitude, electrically determining the frequency of the sound wave. In this embodiment of the present invention, the acoustic output element 5 is configured to emit sound waves having a frequency in the range of at least 2 kHz to 4 kHz.

[0026] (Audio Film 4) The acoustic film 4 is composed of a thin film material molded into a cone shape and plays a role in efficiently transmitting and diffusing sound in an acoustic device. The acoustic film 4 has high conformability to the piezoelectric plate or diaphragm and radiates sound waves to the outside.

[0027] The acoustic film 4 has a frustoconical shape. The acoustic film 4 comprises a bottom portion having a roughly circular shape, a side portion having an inverted cone shape, or a horn or bell shape, with the diameter increasing upward from the bottom, and a flange portion extending from the outer edge of the side portion.

[0028] The bottom of the acoustic film 4 is connected to the diaphragm or piezoelectric element of the acoustic output element 5 by adhesive or the like, so as to transmit vibrations from the acoustic output element 5 to the side of the acoustic film 4. The outer edge of the flange portion of the acoustic film 4 is fixed to the inner surface of the housing 2. The flange portion of the acoustic film 4 is provided with a protrusion to reduce the transmission of vibrations to the housing 2. This protrusion is intended to suppress the vibrations of the acoustic film 4 before they are transmitted to the housing 2, and plays a role in suppressing the transmission of vibration energy and confining the vibrations to the inside of the protrusion. The protrusion is arranged in a ring shape between the outer edge of the flange portion and the side of the acoustic film 4.

[0029] The acoustic film 4 may be formed from a lightweight and highly rigid material such as synthetic resin. The thickness of the acoustic film 4 may be set to provide appropriate rigidity and flexibility, and to properly transmit vibrations from the diaphragm.

[0030] (Substrate opening 33) The substrate opening 33 provided in the substrate 3 will be explained using Figure 3. Figure 3A shows a cross-sectional view of a reference example in which the substrate opening 33 is not provided in the substrate 3. In the reference example, a gap with an opening area S1 exists between the region surrounded by the inner circumferential surface 23 of the housing 2 and the region surrounded by the outer circumferential surface 31 of the substrate 3. Such a gap can be formed by the following: In existing acoustic devices, there are manufacturing tolerances in the dimensions of the housing 2 and the substrate 3, making it difficult to achieve a tight fit, and a certain amount of gap is required in the design. Also, in existing acoustic devices, a small gap is provided between the substrate 3 and the housing 2 to allow for smooth insertion or removal when the substrate 3 is placed in the housing 2. Furthermore, in existing acoustic devices, the presence of a gap allows for airflow around the substrate 3, enabling efficient dissipation of internal heat. A gap is provided between the housing 2 and the substrate 3 so that external shocks and vibrations are suppressed and transmitted to the substrate. In existing acoustic devices, an upper cavity and a lower cavity, separated vertically via a substrate 3, are connected by a gap having an opening area S1.

[0031] Figure 3B shows a cross-sectional view of an acoustic device 1 according to an embodiment of the present application. As shown in Figure 3B, in addition to a gap having an opening area S1, the substrate 3 is provided with a substrate opening 33 that penetrates the substrate 3. The substrate opening 33 has an opening area S2. The substrate opening 33 is provided to improve resonance loss between the upper cavity and the lower cavity.

[0032] (Shape of the substrate opening 33) The shape of the substrate opening 33 will now be described. As shown in Figure 3B, the substrate opening 33 can be a circular opening. A circular shape results in less stress concentration and is easy to manufacture. Also, because sound waves are diffused evenly, resonance loss can be effectively suppressed. Furthermore, the shape of the substrate opening 33 is not limited to a circular shape; it may be a rectangular or square opening. While rectangular or square openings can aim for resonance suppression effects in specific frequency bands, they are prone to stress concentration and may affect the strength of the substrate 3. In addition, the substrate opening 33 can be a polygonal opening. Shapes with multiple corners (such as a hexagon) can be effective in specific frequency bands.

[0033] (Number of substrate openings 33) The number of substrate openings 33 can be any number. For example, providing a single relatively large opening can effectively suppress resonance loss, but on the other hand, it may result in insufficient strength of the substrate 3. Multiple openings can also be provided. Providing multiple openings can further reduce resonance loss. Increasing the number of openings can improve the fluidity of sound waves throughout the substrate 3, thereby preventing the occurrence of resonance loss. However, too many openings will affect the strength of the substrate 3, so it is desirable to design while considering a balance with strength.

[0034] (Position of the substrate opening 33) Regarding the position of the substrate opening 33, it may be placed at any position as long as it does not impair the function of the circuit mounted on the substrate 3. For example, the substrate opening 33 may be placed in the center of the substrate 3. By providing an opening in the center of the substrate 3, the flow of sound waves can be improved in regions where the vibration of the piezoelectric element is relatively large, thereby effectively suppressing resonance loss. However, it is desirable to design the central part to ensure appropriate strength due to the structure of the substrate 3. The substrate opening 33 may also be placed in the peripheral part of the substrate 3. By providing multiple small openings in the peripheral part of the substrate 3, resonance occurring at the edges can be suppressed, and the overall resonance characteristics can be improved. Furthermore, the substrate openings 33 may be randomly arranged. By arranging them randomly, resonance in a specific frequency band can be dispersed, and uniform acoustic characteristics can be obtained over a wide frequency band.

[0035] (Opening area ratio) The method for calculating the opening area ratio will be explained using Figures 3A and 3B. The opening area ratio is calculated as (S1 + S2) / S0 × 100, and the unit is %.

[0036] Here, S0 is the area of ​​the closed region surrounded by the inner circumferential surface 23 of the housing, S1 is the area of ​​the gap between the inner circumferential surface 23 of the housing and the outer surface 31 of the side surface of the substrate, and S2 is the opening area of ​​the substrate opening 33 provided in the substrate 3.

[0037] Next, Figure 4 will be used to explain the aperture area ratio using reference examples and examples.

[0038] Figure 4(a) shows a cross-section of Reference Example 1 where, for example, there is no gap having S1 and no substrate opening 33 having S2, in the case where the opening area ratio is 0%. In this case, it means that there is no substantial communication between the upper cavity and the lower cavity defined vertically through the substrate 3. Therefore, the opening area ratio is 0%.

[0039] Figure 4(b) shows a cross-section of Reference Example 2, in which a gap with area S1 is provided, but no substrate opening 33 is provided in the substrate 3. S2 is 0. In this case, the opening area ratio is determined based on S1, and the opening area ratio is 18.2%.

[0040] Figure 4(c) shows a cross-section of Embodiment 1, which has a gap with the same area S1 as in Figure 4(b), in addition to a substrate opening 33 with a diameter of 5 mm that penetrates the substrate 3. The opening area ratio is 19%.

[0041] Figure 4(d) shows a cross-section of Embodiment 2, which has a gap with the same area S1 as in Figure 4(b), in addition to a substrate opening 33 with a diameter of 10 mm that penetrates the substrate 3. The opening area ratio is 21.3%.

[0042] Figure 4(e) shows a cross-section of Embodiment 3, which has a gap with the same area S1 as in Figure 4(b), in addition to a substrate opening 33 with a diameter of 25.24 mm that penetrates the substrate 3. The opening area ratio is 28.2%.

[0043] Figure 4(f) shows a cross-section of Reference Example 3 when substrate 3 is absent. Since there is no substrate and S1 + S2 = S0, the aperture area ratio is 100%.

[0044] The opening area ratio can be determined by methods such as geometric calculations based on the dimensions and shape of the opening, calculations using CAD software or 3D modeling tools, or calculations based on manual measurement of the size.

[0045] The acoustic effects of the substrate opening 33 provided in the substrate 3 will be explained using the following Tables 1 to 3 and Figures 5 to 8.

[0046] [Table 1]

[0047] Using Table 1, the amount of improvement in the dip around 3.0 kHz in the frequency characteristics of the reference examples illustrated in Figures 4(a) to (f) and the embodiments of the present application will be explained. A dip is a portion in the frequency characteristics where the sound pressure decreases.

[0048] In the left column of Table 1, "Presence or Absence of a Gap" indicates the presence or absence of a gap with area S1 in Figure 4. "No Gap" indicates that area S1 in Figure 4 is 0. The diameter of the substrate opening 33 (mm) represents the diameter of the circular substrate opening 33 that penetrates the substrate 3. The opening area ratio [%] indicates what percentage of the total area of ​​the substrate 3 is occupied by the opening provided in the substrate 3.

[0049] In the left column of Table 1, the sound pressure [dBA] at frequencies around 3.0 kHz indicates the sound pressure level measured for sound waves with frequencies around 3.0 kHz. Sound pressure is a physical quantity that indicates the magnitude of pressure fluctuations that occur when sound waves travel through air or other media, and is expressed in decibels (dBA). A higher value indicates greater sound pressure. In alarm sounds, sound pressure is one of the parameters. For example, high sound pressure makes alarm sounds easier to hear even in noisy environments, effectively transmits alarm sounds over a wide area, makes the urgency more intuitively clear, and makes it less likely for alarm sounds to be blocked by buildings, etc. In the left column of Table 1, the difference [dBA] (percentage) with Reference Example 2 at around 3 kHz indicates the difference in sound pressure level when compared to Reference Example 2. Here, the increase in sound pressure and the percentage increase are expressed in decibels (dBA) and as a percentage, with Reference Example 2 as the baseline. A larger value means a greater improvement in sound pressure.

[0050] (Reference example 2) Reference Example 2 corresponds to the case illustrated in Figure 4(b). In Reference Example 2, where the aperture area ratio is 18.2%, the sound pressure at 3.0 kHz is 111.27 dBA, and other reference examples and embodiments are compared to this as a baseline.

[0051] (Example 1: φ5) Example 1 corresponds to the case where a circular substrate opening 33 with a diameter of 5 mm is provided that penetrates the substrate. Providing a circular opening with a diameter of 5 mm corresponds to an opening area ratio of 19.0%. In this case, the sound pressure is 112.18 dBA, indicating an improvement of 0.91 dBA (11%) in sound pressure compared to Reference Example 2. This shows that increasing the opening area by 0.8% compared to Reference Example 2 also improves the sound pressure.

[0052] (Example 2: φ10) Example 2 corresponds to the case where a circular opening with a diameter of 10 mm is provided through the substrate 3. Providing a circular opening with a diameter of 10 mm corresponds to an opening area ratio of 21.3%. In this case, the sound pressure was 112.49 dBA, an improvement of 1.22 dBA (15%) compared to Reference Example 2. This indicates that the increase in opening area contributes to a further improvement in sound pressure.

[0053] (Example 3: φ25.24) Example 3 corresponds to the case where a circular opening with a diameter of 25.24 mm is provided through the substrate 3. Providing a circular opening with a diameter of 25.24 mm corresponds to an opening area ratio of 28.2%. In this case, the sound pressure reached 112.51 dBA, showing an improvement of 1.24 dBA (15.3%) compared to Reference Example 2. Even in this case, although the increase in opening area has a positive effect on the acoustic characteristics, the degree of improvement is substantially the same as in the case of φ10.

[0054] (Reference example 3) Reference Example 3 corresponds to the case where circuit board 3 is not provided. Although it is not practical to omit circuit board 3, by omitting it, the influence of circuit board 3 on the acoustic characteristics can be eliminated. If circuit board 3 is present, its material and shape may affect the propagation and resonance of sound waves, so by removing circuit board 3, these effects can be avoided and pure acoustic characteristics can be measured. By evaluating the acoustic characteristics without circuit board 3, it is possible to understand how circuit board 3 affects the entire acoustic device. In the case without circuit board 3, the sound pressure reached 112.65 dBA, and an improvement of 1.38 dBA (17.2%) was confirmed compared to Reference Example 2.

[0055] Here, in the case of Example 3 (φ25.24, aperture area ratio 28.2%) and the case of Reference Example 3 (aperture area ratio 100%), despite the aperture area ratio being approximately 3.5 times greater, no significant differences were observed between the two in terms of improvements compared to Reference Example 2. In the "φ25.24" housing, an opening is provided in the circuit board, and the area ratio of this opening is 28.2%. Due to this opening, the circuit board does not completely divide the space inside the housing, and the upper and lower spaces are partially connected. This partial connection mitigates the impact of the presence of the circuit board itself on the acoustic characteristics, and the sound pressure of the sound waves can become close to that of the "no circuit board" case. As a result, it is thought that even though there is a circuit board, the resonance of the space and the decrease in sound pressure are suppressed by the opening, and acoustic characteristics similar to those of the "no circuit board" case are obtained. In addition, by providing an opening, the acoustic disadvantages caused by the circuit board dividing the space are reduced. Resonance loss due to the presence of the circuit board is minimized and sound pressure is improved, so it can exhibit characteristics similar to that of the case without a circuit board. It is thought that this was effective in reducing resonance loss at the φ5 stage.

[0056] (Example 1: No gaps with area S1) Reference Example 1 in the far right column of Table 1 corresponds to a case where the gaps within the enclosure are completely eliminated. For example, this corresponds to a case where the upper cavity and lower cavity are spatially separated by a circuit board. In this "no gaps" case, the sound pressure reached 113.20 dBA, and the largest improvement of 1.93 dBA (24.8%) was confirmed compared to the reference example 2. In this case, since the upper and lower cavities are not connected, there is no resonance loss between the upper and lower cavities, nor is there any leakage of sound waves from the upper cavity to the lower cavity, which is why the sound pressure was the highest among all the examples.

[0057] Using the graph in Figure 5, we will explain in more detail the amount of improvement in the dip around 3.0 kHz in the frequency response shown in Table 1.

[0058] The horizontal axis in Figure 5 represents the aperture area ratio (%). As the aperture area ratio increases, the proportion occupied by substrate 3 decreases, indicating a larger area (S1 + S2). The vertical axis in Figure 5 represents the improvement in sound pressure around 3.0 kHz. The improvement is shown as a percentage; a larger value indicates a greater improvement in sound pressure compared to the reference example 2.

[0059] As shown in Figure 5, the sound pressure improvement rate rises sharply once the aperture area exceeds 18.2%, then slows down around 21.3% (corresponding to Example 2), and remains roughly flat until reaching 100% (corresponding to Reference 3). This result suggests that once an aperture area of ​​approximately 21.3% is secured, the sound pressure improvement effect saturates, and significant improvement through further increases in area becomes difficult.

[0060] When the aperture area ratio exceeds approximately 28%, a slight increase in sound pressure improvement can be observed, but the improvement is minimal, and no significant effect is obtained, indicating that there are limits to the effectiveness of increasing the aperture area.

[0061] The graph in Figure 5 shows that appropriately setting the aperture area affects the improvement of acoustic characteristics, and by selecting the optimal aperture area, unnecessary design changes such as creating an unnecessarily large substrate opening 33 can be avoided. For example, creating an unnecessarily large substrate opening 33 may require redesigning the existing substrate 3 or reducing the size of the circuit elements used in the existing substrate 3, which could result in significant changes to the existing substrate 3. Based on the graph shown in Figure 5, it is possible to make adjustments to obtain optimal acoustic characteristics without making an overall design change to the existing substrate 3. In this way, by utilizing the results obtained from the graph in Figure 5, it is possible to improve the performance of the acoustic device while minimizing overall design changes to the substrate 3 by appropriately setting the substrate opening 33. As a result, design efficiency is improved and cost reduction is also achieved. For example, from the graph in Figure 5, considering the balance between acoustic performance and other design requirements, an aperture area range of 19% to 28.2% that provides an appropriate improvement is considered a practical design option.

[0062] In the graph in Figure 5, a significant improvement was achieved in Reference Example 1, which has a 0% opening area ratio and no gaps, compared to other examples. However, eliminating the gap between the inner surface of the housing 2 and the substrate 3 requires the use of precise manufacturing techniques. This process, which involves assembling parts with high precision, can significantly increase manufacturing costs. It also increases the amount of additional materials and labor required to fill the gaps, making it inefficient for mass production. On the other hand, providing substrate openings 33 in the substrate 3 is easy to implement at the design stage and can be done without making significant changes to existing manufacturing processes, thus being cost-effective. By installing substrate openings 33, complex processes for filling gaps can be avoided, allowing for a balance between manufacturing speed and cost. Furthermore, providing substrate openings 33 in the substrate 3 increases design flexibility. By adjusting the number, size, and shape of the substrate openings 33, it is possible to fine-tune and optimize the acoustic characteristics. This provides flexibility to meet different acoustic requirements and allows for customization to suit specific usage environments and requirements. The method of creating a substrate opening 33 is suitable for mass production, and stable quality can be maintained even when producing many identical substrate designs. Creating a substrate opening 33 on substrate 3 requires few changes to the manufacturing process and is easy to scale up. In contrast, the process of filling gaps is time-consuming and can be an unstable factor in mass production. Also, when filling gaps, the performance of each product may vary depending on how well the gaps are filled. On the other hand, substrate openings 33 on substrate 3 can provide consistently consistent products through design. Depending on the material used to fill the gaps, degradation or shrinkage may occur after long-term use, which may affect the acoustic properties. When substrate openings 33 are created on substrate 3, the risk of such degradation is smaller.

[0063] As shown in the graph in Figure 5, while the structure of Reference Example 1, which has "no gaps," provides the highest sound pressure, achieving it involves significant cost and effort. Therefore, providing a substrate opening 33 in the substrate 3 simplifies the manufacturing process, is more cost-effective, and offers design flexibility, making it a more realistic and practical option for mass-produced products. Since this method also provides a sufficient improvement in acoustic performance, it can be said that "creating an opening" is a superior approach to "filling gaps" in the manufacturing of acoustic devices.

[0064] [Table 2]

[0065] Table 2 is used to explain the improvement in maximum sound pressure in the frequency response at approximately 3.1kHz to 3.2kHz. Specifically, the changes in sound pressure levels based on different design conditions (aperture area ratio, presence or absence of substrate 3, presence or absence of substrate openings) are compared with the improvement effect compared to the reference example 2.

[0066] In the leftmost column of Table 2, the presence or absence of gaps, the diameter of the substrate opening 33 (mm), and the opening area ratio [%] are the same as those in Table 1. In the leftmost column of Table 2, sound pressure [dBA] represents the measured maximum sound pressure level in decibels (dBA). A higher sound pressure level indicates a greater sound pressure from the sound device. In the leftmost column of Table 2, the difference in maximum sound pressure [dBA] (percentage) shows the difference in sound pressure level compared to the reference example 2, and is displayed in decibels (dBA) and its percentage increase. A larger value indicates an improvement in sound pressure.

[0067] (Reference example 2) In a reference example with an aperture area ratio of 18.2%, the maximum sound pressure is 114.42 dBA. This value is used as a baseline for comparison with other design conditions.

[0068] (Example 1: φ5) When the aperture area ratio is 19.0%, the maximum sound pressure is 114.91 dBA, which is an improvement of 0.49 dBA (5.8%) compared to Reference Example 2. This indicates that slightly increasing the aperture area slightly improves the sound pressure.

[0069] (Example 2: φ10) When the aperture area ratio was 21.3%, the maximum sound pressure reached 115.03 dBA, showing an improvement of 0.61 dBA (7.2%) compared to Reference Example 2. Further improvement in sound pressure was confirmed by increasing the aperture area.

[0070] (Example 3: φ25.24) When the aperture area ratio is 28.2%, the maximum sound pressure is 115.12 dBA, showing an improvement of 0.70 dBA (8.4%) compared to Reference Example 2. In this case, the improvement effect of increasing the aperture area is further enhanced.

[0071] (Reference example 3) Without circuit board 3, the maximum sound pressure reaches 115.24 dBA, showing an improvement of 0.82 dBA (9.9%). The absence of circuit board 3 further increases the sound pressure.

[0072] (Reference example 1) In the "no gaps" example 1, the maximum sound pressure reached 115.28 dBA, showing the greatest improvement of 0.86 dBA (10.4%) compared to example 2. In this case, the highest sound pressure is obtained because there is no sound wave leakage or resonance loss between the upper and lower cavities.

[0073] Table 2 clearly shows that increasing the aperture area of ​​substrate 3 improves the maximum sound pressure of the acoustic device. While the improvement in sound pressure tends to increase with increasing aperture area, it is suggested that there is a limit to the improvement effect even when the aperture area is increased beyond a certain point.

[0074] In this regard, the results in Table 1 and the graph in Figure 5 are consistent. Among these, the most effective method is to completely eliminate the gap, in which case the greatest sound pressure improvement is achieved. However, as mentioned above, eliminating the gap and ensuring a tight seal is difficult from a manufacturing standpoint, so it is more appropriate to achieve a realistic and effective sound pressure improvement by providing a substrate opening 33 in the substrate 3.

[0075] Using the graph in Figure 6, we will explain in more detail the improvement in maximum sound pressure in the frequency response shown in Table 2. According to the graph in Figure 6, similar to the graph in Figure 5, the sound pressure improvement rate rises sharply from around an aperture area of ​​18.2%, then becomes more gradual around an aperture area of ​​21.3% corresponding to Example 2, and remains roughly flat until reaching an aperture area of ​​100% corresponding to Reference 3. This result suggests that if an aperture area of ​​around 21.3% can be secured, the improvement effect on maximum sound pressure saturates, and significant improvement by further increasing the area is difficult. Also, for example, from the graph in Figure 6, considering the balance between acoustic performance and other design requirements, an aperture area range of 19% to 28.2% that provides appropriate improvement is considered a practical design option.

[0076] As shown in the graph in Figure 6, similar to the graph in Figure 5, the structure of Reference Example 1, which has "no gaps," provides the highest sound pressure. However, achieving this involves significant costs and effort. Therefore, providing a substrate opening 33 on the substrate 3 simplifies the manufacturing process, is more cost-effective, and offers design flexibility, making it a more realistic and practical option for mass-produced products.

[0077] [Table 3]

[0078] Table 3 describes the improvement achieved when sweep control is used to emit sound waves in the frequency range of 2.6kHz to 3.5kHz, which is the actual frequency range used in real-world applications. Specifically, the changes in sound pressure levels under different design conditions (aperture area ratio, presence or absence of substrate 3, presence or absence of substrate opening 33) are compared with the improvement effect compared to Reference Example 2. Regarding the frequency range, 2.6kHz to 3.5kHz is the frequency band in which the acoustic device operates in real-world environments. 2.6kHz is a relatively low high-pitched sound, and 3.5kHz is an even higher-pitched sound. This band is the core frequency range for many alarm sounds, notification sounds, and acoustic signals, and is also a region to which human hearing responds sensitively. Evaluating the performance in this frequency range confirms how effectively the device emits sound in real-world usage scenarios. By measuring the maximum sound pressure across the entire frequency band using sweep control, it is possible to comprehensively evaluate how the acoustic device radiates acoustic energy.

[0079] In the leftmost column of Table 3, the presence or absence of gaps, the diameter of the substrate opening 33 (mm), and the opening area ratio [%] are the same as those in Table 1. In the leftmost column of Table 3, "Sound pressure [dBA]" is the maximum sound pressure level measured when sweep control was performed so that sound waves from 2.6 kHz to 3.5 kHz were continuously generated, and is expressed in decibels (dBA). A higher sound pressure value indicates that the sound device is outputting a stronger sound. In the leftmost column of Table 3, the difference in maximum sound pressure [dBA] (percentage) shows the difference in sound pressure level compared to Reference Example 2, and the amount of improvement in sound pressure is shown in decibels (dBA) and its percentage increase. A larger value indicates a greater improvement compared to the current product.

[0080] (Reference example 2) In Reference Example 2, where the aperture area ratio is 18.2%, the maximum sound pressure is 114.88 dBA. Other design conditions are compared using this value as a baseline.

[0081] (Example 1: φ5) When the aperture area ratio was 19.0%, the sound pressure reached 115.24 dBA, showing an improvement of 0.36 dBA (4.2%) compared to Reference Example 2. This demonstrates that even a slight increase in aperture area can improve sound pressure.

[0082] (Example 2: φ10) When the aperture area ratio is 21.3%, the sound pressure reaches 115.69 dBA, showing an improvement of 0.81 dBA (9.8%) compared to Reference Example 2. This demonstrates that further improvements in sound pressure can be achieved by increasing the aperture area.

[0083] (Example 3: φ25.24) In a housing with an aperture area ratio of 28.2%, the sound pressure reached 115.75 dBA, showing an improvement of 0.87 dBA (10.5%) compared to Reference Example 2. As the aperture area increases further, the sound pressure improvement effect continues to improve.

[0084] (Example 3: No circuit board) In enclosures without circuit board 3, the sound pressure reaches 115.77 dBA, showing an improvement of 0.89 dBA (10.8%). This indicates that the sound pressure is even higher due to the absence of the influence of circuit board 3.

[0085] (Example 1: No gaps) When the gap is completely eliminated, the sound pressure reaches 115.90 dBA, showing a maximum improvement of 1.02 dBA (12.5%) compared to Reference Example 2. In this case, it is thought that the highest sound pressure was obtained because there is no sound wave leakage or resonance loss between the upper and lower cavities.

[0086] Table 3 clearly shows that increasing the aperture area ratio improves the maximum sound pressure of the acoustic device 1 in sweep control from 2.6kHz to 3.5kHz. While there is a tendency for the sound pressure improvement effect to increase with increasing the aperture area, it is suggested that there is a limit to the improvement effect even if the aperture area is increased beyond a certain point. In this respect, the results in Table 1 and the graph in Figure 5, as well as the results in Table 2 and the graph in Figure 6, are consistent. Among these, the most effective is to completely eliminate the gap, in which case the maximum sound pressure improvement is achieved. However, as mentioned above, eliminating the gap and ensuring a tight fit is difficult from a manufacturing standpoint, so it is considered more appropriate to achieve a realistic and effective sound pressure improvement by providing a substrate opening 33 in the substrate 3.

[0087] Using the graph in Figure 7, we will explain in more detail the improvement in maximum sound pressure in the frequency characteristics of sweep control that continuously emits sound waves with frequencies of 2.6kHz to 3.5kHz as shown in Table 3. According to the graph in Figure 6, similar to the graph in Figure 5, the sound pressure improvement rate increases sharply from around an aperture area of ​​18.2%, becomes more gradual around an aperture area of ​​21.3% corresponding to Example 2, and remains roughly flat until reaching an aperture area of ​​100% corresponding to Reference 3. This result suggests that if an aperture area of ​​around 21.3% can be secured, the improvement effect on maximum sound pressure saturates, and significant improvement by further increasing the area is difficult. Also, for example, from the graph in Figure 7, considering the balance between acoustic performance and other design requirements, an aperture area range of 19% to 28.2% that provides appropriate improvement is considered a practical design option.

[0088] As shown in the graph in Figure 7, similar to the graphs in Figures 5 and 6, the structure of Reference Example 1, which has "no gaps," provides the highest sound pressure. However, achieving this involves significant costs and effort. Therefore, providing a substrate opening 33 on the substrate 3 simplifies the manufacturing process, is more cost-effective, and offers design flexibility, making it a more realistic and practical option for mass-produced products.

[0089] Based on the results from Tables 1 to 3 and Figures 5 to 7, it is preferable that the aperture area ratio be in the range of, for example, 19% to 28.2%. This increases design flexibility, making it possible to accommodate devices with different acoustic characteristics, and allowing for easy adjustment of the acoustic equipment to suit different environments. Furthermore, a wide range of aperture areas can improve acoustic efficiency.

[0090] Furthermore, the aperture area ratio is preferably in the range of, for example, 19.0% to 21.3%. Setting a relatively narrow range for the aperture area ratio allows for more precise control of acoustic characteristics. This is advantageous when you want to enhance a specific frequency band or acoustic effect, and is ideal for device design where acoustic balance and quality are important.

[0091] Furthermore, the aperture area ratio is preferably in the range of, for example, 21.3% to 28.2%. Setting a relatively large aperture area ratio makes it possible to obtain higher sound pressure, making it suitable for situations where high volume is output or sound needs to be diffused over a wide area. It also improves airflow and heat dissipation, increasing the durability and stability of the device. This range is effective when a powerful acoustic effect is desired. By setting these aperture area ratios, the performance and characteristics of the acoustic device can be adjusted, enabling optimal acoustic design according to the application.

[0092] Figure 8 is a graph showing the relationship between frequency (kHz) and sound pressure (dBA) for reference example 2 (aperture area ratio 18.2%), example 3 (aperture area ratio 28.2%), and reference example 1 (aperture area ratio 0%). The horizontal axis represents frequency, and the fluctuation in sound pressure is shown in the range of 2.4kHz to 3.6kHz. The vertical axis represents sound pressure level, and dB (decibels) is shown relative to N (reference sound pressure).

[0093] The solid line shows the sound pressure characteristics for the reference example 2 (aperture area ratio of 18.2%). A dip is observed around 3kHz, indicating a decrease in sound pressure. Peaks are also visible around 2.7kHz and 3.15kHz.

[0094] The dashed line shows the sound pressure characteristics for Example 3 (aperture area ratio of 28.2%). Comparing Example 3 with the reference example 2, it can be seen that the sound pressure is generally higher between approximately 2.66kHz and 3.27kHz. Also, the peak structure around 2.9kHz is more pronounced compared to reference example 2. Furthermore, although a dip exists around 3kHz, similar to reference example 2, the depth of the dip around 3kHz is shallower compared to the peaks around 2.7kHz and 3.15kHz in reference example 2. It is possible that the dip around 3kHz was filled in by the presence of the more pronounced peak around 2.9kHz in Example 3. It is also possible that the depth of the dip around 3kHz became shallower due to the suppression of resonance loss.

[0095] The dashed line between Example 3 (aperture area ratio 28.2%) and Reference Example 2 (aperture area ratio 18.2%) shows the sound pressure characteristics for Example 2 (aperture area ratio 21.3%). This frequency characteristic shows the frequency characteristics of Reference Example 2 with increased intensity.

[0096] Figure 8 shows the frequency-dependent sound pressure characteristics. Regarding the relationship between increasing the aperture area ratio and sound pressure, increasing the aperture area ratio from 18.2% to 28.2% improved the sound pressure overall, with a significant improvement observed in the frequency range of 2.66 kHz to 3.27 kHz. This indicates an improvement in the performance of the acoustic device 1. Although a dip around 3 kHz still remains, it was shown that the relative depth of the dip can be reduced. Regarding the effect of gaps, it was confirmed that in the gap-free state, the sound pressure loss was greatly improved and the maximum sound pressure was obtained. This indicates that gaps can negatively affect sound transmission, but suggests that optimizing the aperture area ratio affects acoustic performance. It was shown that sound pressure can be effectively improved by adjusting the aperture area ratio. Although the "gap-free" state, which corresponds to an aperture area ratio of 0%, shows the highest sound pressure, eliminating gaps is not always practical in actual design and manufacturing processes, so appropriate adjustment of the aperture area ratio is desirable. Such adjustment can be achieved by providing substrate openings 33 in the substrate 3. The approach of creating a substrate opening 33 is a more realistic and practical option for mass-produced products because it simplifies the manufacturing process, is cost-effective, and offers design flexibility. Furthermore, this method also yields sufficient acoustic performance improvement comparable to Reference Example 1, which showed the highest improvement rate. Therefore, in the manufacturing of the acoustic device 1, "creating an opening" is a superior approach to "filling the gap." [Industrial applicability]

[0097] This disclosure is suitable as an acoustic device that emits an alarm sound. [Explanation of Symbols]

[0098] 1 Sound equipment 2 cabinets 3 circuit boards 4. Acoustic Film 5. Acoustic output element 21 Upper cabinet 22 Lower cabinet 23 Inner surface 31 External surface 33 Substrate opening

Claims

1. A circuit board equipped with a circuit that generates a drive signal to produce sound waves, A housing that houses the aforementioned circuit board inside, Equipped with, The substrate is positioned to divide the space within the housing into an upper cavity and a lower cavity. The upper cavity and the lower cavity are in communication through an opening. The sound device is characterized in that the opening includes a substrate opening that penetrates the substrate.

2. The sound device according to claim 1, characterized in that the opening includes a gap between the inner surface of the housing and the substrate.

3. The sound device according to claim 2, characterized in that the ratio of the opening area of ​​the opening, which consists of the substrate opening and the gap, to the area of ​​the space surrounded by the inner surface of the housing is 19% or more and 28.2% or less.

4. The sound device according to claim 2, characterized in that the ratio of the opening area of ​​the opening, which consists of the substrate opening and the gap, to the area of ​​the space surrounded by the inner surface of the housing is 19.0% or more and 21.3% or less.

5. The sound device according to claim 2, characterized in that the ratio of the opening area of ​​the opening, which consists of the substrate opening and the gap, to the area of ​​the space surrounded by the inner surface of the housing is 21.3% or more and 28.2% or less.

6. The sound device according to claim 1, characterized in that the substrate opening has a circular shape.

7. The sound device according to claim 1, characterized in that the substrate opening has a polygonal shape.

8. The sound device according to claim 1, characterized in that a plurality of the aforementioned substrate openings are provided.

9. The sound device according to claim 1, characterized in that the substrate opening is provided in the central part of the substrate.

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