Underwater Helmholtz silencer with wide working frequency band

Abstract

The utility model designs an underwater Helmholtz silencer with a wide working frequency band. Comprising a main pipeline, a neck part, a resonant cavity, a cross-shaped sound absorption structure and an air bag structure. The low-frequency resonance frequency of the Helmholtz muffler can be reduced by increasing the sound inertia and reducing the sound rigidity, the muffling frequency is close to the low frequency, and the effective muffling working frequency band is widened. And the change amplitude of the resonant frequency of the Helmholtz silencer can be controlled by selecting sound absorption structures made of different materials and filling different gases into the air bag, so that the silencing effect on a specific working frequency band is realized. The problem that the low-frequency resonance frequency of the Helmholtz silencer is reduced to achieve the effective silencing effect of a wider frequency band is solved.

Description

Technical Field

[0001] The utility model belongs to the field of muffler devices, and in particular relates to an underwater Helmholtz muffler with a wide working frequency band. Background Art

[0002] Current Helmholtz silencers are commonly used in HVAC systems, mechanical equipment, transportation, audio equipment, and other fields. Due to specific needs, a variety of Helmholtz resonance-based silencer designs and products are now available on the market. These include multi-cavity Helmholtz silencers, which are composite structures composed of multiple Helmholtz cavities that control noise across a wider frequency range through cavities of varying sizes and arrangements; and membrane Helmholtz silencers, which incorporate a vibrating membrane at the inlet or outlet of a resonant wall, enhancing the sound attenuation effect through the membrane's vibration characteristics.

[0003] The utility model provides an underwater Helmholtz muffler with a wide operating frequency band, which solves the problem of achieving an effective muffler effect in a wider frequency band by reducing the low-frequency resonance frequency of the Helmholtz muffler. Utility Model Content

[0004] The purpose of the utility model is to provide an underwater Helmholtz muffler with a wide operating frequency band.

[0005] The purpose of the utility model is achieved through the following technical solutions:

[0006] An underwater Helmholtz muffler with a wide operating frequency band comprises a muffler shell, a main pipe and a resonance cavity are provided inside the muffler shell, a passage leading to the resonance cavity is provided in the middle of the main pipe, a neck is provided at the entrance of the passage inside the resonance cavity, and a cross-shaped sound absorbing structure and an airbag structure are provided inside the resonance cavity; the lower part of the cross-shaped sound absorbing structure blocks the passage between the main pipe and the resonance cavity, the upper end of the cross-shaped sound absorbing structure is connected to the inner wall of the resonance cavity by a spring, and the bottom surfaces of the left and right ends of the cross-shaped sound absorbing structure are connected to the neck by a spring; the airbag structure is connected to the outside of the muffler shell through an inflation hole.

[0007] Furthermore, the cross-shaped sound absorbing structure has a wide lower portion adapted to the neck, and a narrow upper portion and left and right portions.

[0008] Furthermore, the airbag structures are distributed on both sides of the resonance cavity.

[0009] Furthermore, the airbag structure and the resonance cavity are separated by a perforated plate.

[0010] Furthermore, there are two groups of resonance cavities, which are located on the upper and lower sides of the main pipe respectively. The two groups of airbag structures in the upper resonance cavity are connected to the outside of the muffler shell through inflation holes, and the two groups of airbag structures in the lower resonance cavity do not have inflation holes.

[0011] The beneficial effects of the present invention are:

[0012] 1. By increasing the acoustic inertia and reducing the acoustic stiffness, the low-frequency resonance frequency of the Helmholtz muffler is reduced, and the muffler frequency is moved closer to the low frequency, thereby widening the effective muffler working frequency band.

[0013] 2. By selecting sound-absorbing structures of different materials and filling the airbag with different gases, the change amplitude of the resonant frequency of the Helmholtz muffler can be controlled to achieve the noise reduction effect in a specific working frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a cross-sectional view of the overall structure of an underwater Helmholtz muffler with a wide operating frequency band according to the present invention; DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings.

[0016] It should be noted that, unless otherwise specified, the relative arrangement of components and steps, numerical expressions, and numerical values ​​described in these embodiments do not limit the scope of the present invention. Obviously, the described embodiments are only a portion of the embodiments of the present invention, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0017] See Figure 1 The utility model provides a technical solution: an underwater Helmholtz muffler with a wide working frequency band.

[0018] The device comprises a main pipe 1, a neck 2, a resonant cavity 3, a cross-shaped sound-absorbing structure 4, and an airbag structure 5. The neck 2 is connected to a cross-shaped sound-absorbing structure 4, which is connected to the resonant cavity by a spring. The airbag structures are installed on both sides of the resonant cavity and separated from the central cavity by a perforated plate.

[0019] The cross-shaped sound-absorbing structure 4 should use viscoelastic sound-absorbing materials, occupying the entire space of the neck 2, which can effectively increase the acoustic inertia of the muffler. The cross-shaped sound-absorbing structure 4 is connected to the resonance cavity with a spring to reduce the impact on the structural vibration of the muffler.

[0020] The airbag structure 5, installed on either side of the resonance cavity 3, provides a certain degree of sound attenuation. Separated from the central cavity by appropriately designed perforated plates, the airbag structure 5 acts as a limiter while also enhancing the device's vibration isolation performance. By displacing the water previously present within the resonance cavity, the airbag structure 5 effectively reduces the muffler's acoustic stiffness.

[0021] The noise enters the resonance cavity 3 from the main pipe 1 through the neck 2, and after the resonance effect occurs, it plays a role in noise reduction.

[0022] The cross-shaped sound absorbing structure 4 is installed at the neck 2 and extends into the resonance cavity 3. The cross-shaped sound absorbing structure 4 is connected to the boundary of the resonance cavity 3 by a spring, which not only plays a limiting role but also avoids affecting the vibration of the muffler.

[0023] The airbag structure 5 is respectively arranged on both sides of the resonance cavity 3, and is connected to the inflation hole on the outside. The airbag structure 5 is separated from the cavity part of the resonance cavity 3 by a perforated plate. The perforated plate adopts an appropriate design, which not only plays a limiting role, but also is beneficial to the vibration isolation performance of the muffler.

[0024] A Helmholtz resonator is a device that operates based on the principle of resonance. Within a Helmholtz muffler, acoustic inertia and acoustic stiffness interact to form a resonant structure similar to a spring-oscillator system. The fluid mass within the resonator vibrates in response to the sound waves, and the compressibility of the resonator maximizes the vibrations. When the external sound wave frequency equals the resonator's resonant frequency, the acoustic inertia and acoustic stiffness are optimally matched, amplifying the resonance effect.

[0025] Acoustic inertia can be understood as the mass of the air within the resonant cavity. When an external sound wave enters the resonant cavity, the fluid mass begins to vibrate, similar to the mass in a spring-oscillator system. The fluid mass within the resonant cavity vibrates with the frequency of the sound wave. At the resonant frequency, the vibration amplitude of the air mass within the resonant cavity reaches its maximum. Acoustic stiffness, on the other hand, is similar to the spring stiffness in a spring system; it represents the fluid's resistance to compression. In a Helmholtz muffler, acoustic stiffness can be understood as the compressibility of the internal fluid. When an external sound wave acts on the resonant cavity, the fluid is compressed, and the compressibility of the resonant cavity reaches its maximum at the resonant frequency.

[0026] By increasing the acoustic inertia and reducing the acoustic stiffness, this utility model can reduce the low-frequency resonance frequency of the Helmholtz muffler, shifting the muffler frequency closer to low frequencies and broadening the effective muffler operating frequency band. Furthermore, by selecting sound-absorbing structures made of different materials and filling the airbag with different gases, the amplitude of the Helmholtz muffler's resonant frequency can be controlled to achieve muffler effects within specific operating frequency bands.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An underwater Helmholtz muffler with a wide operating frequency band, characterized by: The invention comprises a muffler shell, wherein a main pipe (1) and a resonance cavity (3) are provided inside the muffler shell, a passage leading to the resonance cavity (3) is provided in the middle of the main pipe (1), a neck (2) is provided at the entrance of the passage inside the resonance cavity (3), and a cross-shaped sound absorbing structure (4) and an air bag structure (5) are provided inside the resonance cavity (3); the lower part of the cross-shaped sound absorbing structure (4) blocks the passage between the main pipe (1) and the resonance cavity (3), the upper end of the cross-shaped sound absorbing structure (4) is connected to the inner wall of the resonance cavity (3) through a spring, and the bottom surfaces of the left and right ends of the cross-shaped sound absorbing structure (4) are connected to the neck (2) through a spring; and the air bag structure (5) is connected to the outside of the muffler shell through an inflation hole.

2. The underwater Helmholtz muffler with a wide operating frequency band according to claim 1, characterized in that: The cross-shaped sound absorbing structure (4) has a wide lower portion adapted to the neck (2), and a narrow upper portion and two left and right portions.

3. The underwater Helmholtz muffler with a wide operating frequency band according to claim 1, characterized in that: The airbag structures (5) are distributed on both sides of the resonance cavity (3).

4. The underwater Helmholtz muffler with a wide operating frequency band according to claim 3, characterized in that: The airbag structure (5) and the resonance cavity (3) are separated by a perforated plate.

5. The underwater Helmholtz muffler with a wide operating frequency band according to claim 4, characterized in that: There are two groups of resonance cavities (3), which are respectively located on the upper and lower sides of the main pipe (1), wherein the two groups of airbag structures (5) in the upper resonance cavity (3) are connected to the outside of the muffler shell through inflation holes, and the two groups of airbag structures (5) in the lower resonance cavity (3) do not have inflation holes.

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