Active noise reduction device

Abstract

The present invention discloses an active noise elimination device, including a driver, a box, an acoustic network, a cavity, a first sound pickup module, an audio processor module and a power amplifier module, wherein the driver and the cavity are arranged in the box, the front of the driver is sealed and connected to the cavity, the acoustic network is installed on the box, the acoustic network is arranged on the rear side of the driver, the first sound pickup module is arranged outside the box, the first sound pickup module is electrically connected to the audio processor module, the audio processor module is electrically connected to the power amplifier module, and the power amplifier module is electrically connected to the driver. The present invention can achieve the purpose of eliminating low-frequency standing waves in a room, improve the reverberation inside the room, and greatly improve the sound recording quality.

Description

Technical Field

[0001] The invention belongs to the technical field of noise reduction, and in particular relates to an active noise reduction device. Background Art

[0002] In the field of traditional recording, in order to improve the standing waves, reverberation and reflection effects in the room, passive sound-absorbing devices are often placed in the four corners of the room. The cavity is filled with sound-absorbing materials to improve the low-frequency sound absorption quality and reduce the impact of standing waves in the corners. The outer surface is processed at an arc angle to expand the diffusion surface. However, this passive sound-absorbing device is affected by the low-frequency wavelength, is bulky, has a high cost, and is not conducive to portable transportation. Summary of the invention

[0003] In view of the problems in the background, the purpose of the present invention is to provide an active noise reduction device, which can eliminate low-frequency standing waves in the room, improve the reverberation inside the room, and greatly improve the sound recording quality.

[0004] To achieve the above-mentioned objectives, the present invention provides an active noise reduction device, including a driver, a box, an acoustic network, a cavity, a first sound pickup module, an audio processor module and a power amplifier module, wherein the driver and the cavity are arranged in the box, the front of the driver is sealed and connected to the cavity, the acoustic network is installed on the box, the acoustic network is arranged on the rear side of the driver, the first sound pickup module is arranged outside the box, the first sound pickup module is electrically connected to the audio processor module, the audio processor module is electrically connected to the power amplifier module, and the power amplifier module is electrically connected to the driver.

[0005] Preferably, the device further comprises a current feedback module and a voltage feedback module, wherein the current feedback module and the voltage feedback module are electrically connected to the driver respectively, and the current feedback module and the voltage feedback module are electrically connected to the audio processor module respectively.

[0006] Preferably, the device further comprises a second sound pickup module, the second sound pickup module is disposed in the box, and the second sound pickup module is electrically connected to the audio processor module.

[0007] Preferably, at least one of the first sound pickup modules is provided, or at least one of the first sound pickup modules is provided and at least one of the second sound pickup modules is provided.

[0008] Preferably, the device further comprises a storage module, and the storage module is electrically connected to the audio processor module and the power amplifier module respectively.

[0009] Preferably, the device further comprises a third sound pickup module, wherein the third sound pickup module is installed in the cavity, and the third sound pickup module is electrically connected to the audio processor module.

[0010] Preferably, the cavity is filled with sound absorbing material.

[0011] Preferably, the audio processor module includes a DSP processing part for filtering frequencies outside the range of 15 Hz to 200 Hz.

[0012] Preferably, the air flow resistance characteristic of the acoustic network is 100 Pa·s / m.

[0013] Preferably, the opening size of the acoustic network is 3mm*0.2mm, and the opening rate is 5-8%.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The first pickup module outside the sound network detects the sound pressure in the room, performs acoustic characteristic impedance matching through the audio processor module, restores the sound pressure through the power amplifier module, and plays it through the driver to eliminate the low-frequency standing waves in the room, improve the reverberation inside the room, and greatly improve the sound recording quality.

[0016] 2. Small size, strong portability, low cost, and large equivalent silencing area;

[0017] 3. The sound pressure restored by the driver is detected by the second sound pickup module, compared with the sound pressure outside the sound network, and the output of the driver is controlled to form a closed-loop detection;

[0018] 4. Providing multiple first sound pickup modules and second sound pickup modules can improve detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the present invention;

[0020] Figure 2 It is a schematic diagram of module connection of the present invention.

[0021] Markings in the attached figure: 1. driver; 2. cabinet; 3. sound network; 4. cavity; 5. first sound pickup module; 6. second sound pickup module; 7. audio processor module; 8. power amplifier module; 9. sound-absorbing material; 10. storage module. DETAILED DESCRIPTION

[0022] In order to make the technical solution of the present invention more clear, the present invention is further described in detail in conjunction with the following examples. It should be understood that the specific embodiments described herein are only used to explain the invention and are not used to limit the present invention.

[0023] According to the vertical incidence model of sound waves, when there are two different media, as long as the fluid characteristic impedance of the two media is equal, then for the propagation of sound, the interface between the media is as if it does not exist, just like entering a black hole and being absorbed, the sound waves are not emitted and are all transmitted.

[0024] Embodiment 1

[0025] Refer to the attached Figure 1 An active noise reduction device includes a driver 1, a box 2, an acoustic network 3, a cavity 4, a first sound pickup module 5, a second sound pickup module 6, an audio processor module 7, a power amplifier module 8 and a storage module 10. The power amplifier module 8 includes a gain module 801 and a power module 802.

[0026] The cavity 4 is arranged at the rightmost side in the box body 2, and the front side of the driver 1 is sealed and connected to the cavity 4. The driver 1 and the cavity 4 form a sealed area as a whole. Since the inside of the cavity 4 is sealed, the sound waves played by the front side of the driver 1 will not be transmitted out of the cavity 4.

[0027] Furthermore, the cavity 4 described in this embodiment is filled with a sound-absorbing material 9. The sound-absorbing material 9 is mainly glass fiber wool, rock wool, egg wool, polyester fiber wool, etc. The sound-absorbing material 9 is mainly used to reduce the Q value of the resonant frequency after the acoustic coupling between the driver 1 and the cavity 4. The lower the Q value, the larger the low-frequency bandwidth range, and the better the active sound absorption effect of the entire product in the low-frequency band of 15Hz to 200Hz.

[0028] The sound waves played by the driver 1 from the front are absorbed by the sound-absorbing material 9 inside the cavity 4 and will not be transmitted outside the cavity 4 .

[0029] The back of the driver 1 will also radiate anti-phase sound waves with the same sound pressure as the forward direction, which will be transmitted out of the box 2 through the sound network 3.

[0030] The acoustic network 3 is installed on the left side of the box 2. The first sound pickup module 5 is arranged outside the box 2, that is, outside the acoustic network 3. The second module is arranged inside the box 2, that is, inside the acoustic network 3.

[0031] The first sound pickup module 5, specifically a microphone, is used to detect the sound pressure outside the acoustic network. When the first sound pickup module 5 senses no signal or does not reach the set threshold, the device described in this embodiment is in a standby state. When the sound pressure outside the acoustic network reaches the threshold, the device starts to work, and the first sound pickup module 5 transmits the detected signal to the audio processor 7 for processing, and then amplifies the signal through the power amplifier module 8 to restore it to the driver 1. The threshold value described in this embodiment is the sensitivity or sound pressure value corresponding to the low frequency band of 15Hz to 200Hz.

[0032] The second sound pickup module 6, specifically a microphone, is used to detect the sound pressure inside the acoustic network.

[0033] Refer to the attached Figure 2 The first sound pickup module 5 and the second sound pickup module 6 are electrically connected to the audio processor module 7 respectively, the audio processor module 7 is electrically connected to the power amplifier module 8, and the power amplifier module 8 is electrically connected to the driver 1.

[0034] The device described in this embodiment also includes a power module for supplying power to the circuit, an MCU for controlling the circuit, and an LED light module for emitting light to indicate when the power module is closed and the device starts working.

[0035] The audio processor module 7 described in this embodiment includes a DSP processing part, which performs filtering processing on frequencies outside 15Hz~200Hz and adjusts the gain value of the output level of this frequency band, thereby improving the sensitivity of the device described in this embodiment in the low frequency band of 15Hz~200Hz.

[0036] The storage module 10 is electrically connected to the audio processor module 7 and the power amplifier module 8 through the MCU. The second sound pickup module 6 detects the sound pressure restored by the driver 1, and also transmits the detected signal to the audio processor 7 for processing. After the audio processor 7 processes the signals detected by the first sound pickup module 5 and the second sound pickup module 6 respectively, it is transmitted to the built-in software of the storage module 10 through the MCU for analysis and judgment. When the sound pressure restored by the driver 1 returned by the storage module 10 is less than the result of the external sound pressure of the sound network, the MCU controls the gain module 801 to increase the output gain, which is amplified by the power module 802 and then output by the driver 1 to form a closed-loop detection, so that the sound pressure value restored by the driver 1 is always consistent with the external sound pressure value of the sound network, and the phase is opposite, so as to achieve a stable active sound absorption effect. Since the circuit loop has ultra-low latency, active noise reduction can be realized in real time.

[0037] The number of the first sound pickup module 5 and the second sound pickup module 6 can be more than one, thereby improving the detection accuracy of the sound pressure restored by the driver 1 being lower than the sound pressure outside the sound network and the sound pressure restored by the driver 1. However, correspondingly, the product structure is more complicated and the cost is increased.

[0038] In other embodiments, the second pickup module 6 can be replaced by a combination of a current feedback module and a voltage feedback module. The current feedback module and the voltage feedback module are electrically connected to the driver 1, respectively, and the current feedback module and the voltage feedback module are electrically connected to the audio processor module 7, respectively. The vibration signal of the driver 1 is detected by voltage feedback at both ends of the driver 1 coil and current feedback at both ends of the driver 1 coil, and the MCU controls the output of the driver 1 by comparing the external sound pressure of the acoustic network and the vibration signal of the driver 1. However, the detection accuracy of this solution is reduced, and the active sound absorption effect is not as good as that of this embodiment.

[0039] In other embodiments, the device may further include a third sound pickup module, specifically a microphone. The third sound pickup module is installed in the cavity 4, and the third sound pickup module is electrically connected to the audio processor module 8. The third sound pickup module is used to detect the sound pressure inside the cavity, thereby determining the sound pressure adjustment inside the cavity 4.

[0040] The inside of cavity 4 is a pressure field, and the outside of cavity 4 (i.e., inside and outside the acoustic network) is a free field. The two feedback principles are different, and it is not recommended to use a third pickup module. Because the pressure inside cavity 4 is very high when driver 1 vibrates, it is easy to damage the condenser microphone diaphragm. In addition, the active noise reduction on the acoustic network 3 is adjusted by the free field and cannot be achieved by the pressure field.

[0041] In this embodiment, the acoustic mesh 3 needs to meet the air flow resistance characteristic of 100Pa·s / m, the size of the acoustic mesh hole is 3*0.2mm, and the opening rate is 5% to 8%. The air flow resistance characteristic of each acoustic mesh hole is the same, and the sound pressure inside the acoustic mesh 3 is evenly distributed.

[0042] The air flow resistance characteristics of the acoustic network can expand the sound pressure on the surface of the driver 1 to the interior of the entire acoustic network 3, that is, the sound absorption area will be much larger than the surface area of ​​the driver 1, achieving the characteristic of a large indoor sound absorption area and dispersing the sound absorption area in the form of a spherical wave.

[0043] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An active noise reduction device, It is characterized in that The invention comprises a driver, a housing, an acoustic network, a cavity, a first sound pickup module, an audio processor module and a power amplifier module, wherein the driver and the cavity are arranged in the housing, the front of the driver is sealed and connected to the cavity, the acoustic network is installed on the housing, the acoustic network is arranged on the rear side of the driver, the first sound pickup module is arranged outside the housing, the first sound pickup module is electrically connected to the audio processor module, the audio processor module is electrically connected to the power amplifier module, and the power amplifier module is electrically connected to the driver; and also comprises a storage module, which is electrically connected to the audio processor module and the power amplifier module respectively.

2. The active noise reduction device according to claim 1, It is characterized in that It also includes a current feedback module and a voltage feedback module, wherein the current feedback module and the voltage feedback module are electrically connected to the driver respectively, and the current feedback module and the voltage feedback module are electrically connected to the audio processor module respectively.

3. The active noise reduction device according to claim 1, It is characterized in that It also includes a second sound pickup module, which is arranged in the box body and is electrically connected to the audio processor module.

4. The active noise reduction device according to claim 2 or 3, It is characterized in that At least one of the first sound pickup modules is provided, or at least one of the first sound pickup modules is provided and at least one of the second sound pickup modules is provided.

5. The active noise reduction device according to claim 1, It is characterized in that It also includes a third sound pickup module, which is installed in the cavity and is electrically connected to the audio processor module.

6. The active noise reduction device according to claim 1, It is characterized in that The cavity is filled with sound absorbing material.

7. The active noise reduction device according to claim 1, It is characterized in that The audio processor module includes a DSP processing part for filtering frequencies outside the range of 15 Hz to 200 Hz.

8. The active noise reduction device according to claim 7, It is characterized in that The air flow resistance characteristic of the acoustic network is 100 Pa·s / m.

9. The active noise reduction device according to claim 8, It is characterized in that The opening size of the acoustic network is 3mm*0.2mm, and the opening rate is 5-8%.

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