TWI530652B - Frequency adjustable noise suppression system - Google Patents

Description

Adjustable frequency sound reduction system

The present invention discloses a sound reduction system, and more particularly to a sound reduction system that can be applied to an adjustable frequency for sound reduction for a particular noise frequency.

The cooling tower is the core component of the air conditioning system, but its low frequency noise is the most difficult to suppress in the environmental noise. The reason is that the low frequency noise of the cooling tower is characterized by surface acoustic waves, and the noise penetration is extremely strong and The mixed noise of the frequency band is difficult to eliminate with a simple sound reduction device, so its noise control technology is more important. However, it is known from the performance graph of the water tower fan that the pressure is the influence factor of the air volume. Therefore, in order to maintain the cooling capacity of the cooling tower system, it is necessary to ensure the pressure to avoid excessive pressure drop and cause the system to dissipate heat efficiently.

However, one of the reasons for the formation of aerodynamic noise is the airflow flowing in the middle of the fan blade passage, which is more likely to generate turbulence when the airflow leaves the trailing end of the blade; the airflow flowing therethrough is compressed due to the rotation of the impeller. The ambient gas pressure is thus rapidly changed to form a noise; and the airflow is subjected to periodic pressure changes due to impact of the blades to form a specific frequency of noise.

For the low-frequency noise transmitted through the air, unless the noise reduction device is directly added to the noise source to reduce the low-frequency noise, it is necessary to start from the sound isolation, but when the conventional absorption or reflection muffler is directly applied to the noise source, it will affect the row. The flow of gas flow greatly increases the system pressure loss. In addition, the absorption muffling equipment with a large number of sound absorbing materials will greatly increase the system load. For the cooling system with high floors, the above-mentioned overload silencer cannot be added. . However, if the sound isolation is taken into consideration, for the high-floor cooling system, a large-area sound insulation facility (sound insulation wall) is required. In addition to the high wind pressure factor that the sound insulation facility must be considered, the related cost will be greatly improved. However, its sound reduction effect is not effective. Therefore, from the viewpoint of noise control, the use of low-voltage loss wide-band tuning silencer to reduce the sound of air and related fluid transport is a subject worthy of discussion.

In view of the above, there are many reasons for the formation of aerodynamic noise. It is not easy to find out the real cause of the aerodynamic noise from the aerodynamic noise itself. Therefore, it is not directly related to the conventional absorption or reflection muffler with large weight and high voltage loss. To suppress noise, a more effective method is to use a low-voltage loss wide-band tuning silencer to deal with aerodynamic noise.

Conventional absorption type sound absorbing devices are designed to reduce the range in a range of frequency ranges, and are not intended to suppress specific noise frequencies. However, the range-type sound absorbing devices of the cover type have a significant noise to the medium and high frequency bands. The effect, but the suppression of low frequency noise can not achieve the desired effect.

Conventional reflective sound attenuating devices are designed to reduce the range in a range of frequency ranges, and are not intended to suppress specific noise frequencies. However, the range-type sound attenuating devices have a significant effect on low-frequency noise. However, the suppression of medium and high frequency noise does not produce the desired effect.

In view of the above, an object of the present invention is to provide a sound reduction system structure capable of reducing the generation of aerodynamic noise, and to effectively deal with the above-mentioned problem of wide frequency aerodynamic noise with its simple design. The embodiments of the present invention are directed to an adjustable frequency sound reduction system. The present invention performs appropriate sound reduction device design for noise of various specific frequencies, and further adopts a modular design to reduce system installation cost.

The invention proposes to improve the sound reduction efficiency of the conventional sound reduction device by using a series multi-column tuner combined with the sound reduction mechanism of the connecting tube. The invention is based on the plane wave propagation theory and is combined with the four-turn transmission matrix to derive the sound attenuation mechanism. The analytic function of the sound transmission loss value of the sound reduction device to improve the sound reduction efficiency of the sound reduction device and adjust the range of the audio reduction rate.

The adjustable frequency sound reduction system of the present invention respectively performs noise reduction processing for noise of different frequencies, and the adjustable frequency sound reduction system comprises a detachable assembled complex array tuning mechanism, and the complex array tuning mechanism respectively corresponds to a plurality of specific The noise frequency, wherein each complex array tuning mechanism comprises: a plurality of tuner, each of the plurality of tuners comprising a single tuning cavity or a combination of a tuning cavity and a sound absorbing body, wherein the sound absorbing body is filled in the tuning cavity, By adjusting the length of the tuning cavity, the sectional area and the filling position of the sound absorbing body to respectively eliminate the corresponding plurality of specific frequencies; the porous shell plate to fix a plurality of tuners; and the outer shell structure, the fixed porous shell plate and the plural A tuner; wherein the complex array tuning mechanism calculates the size of the tuning cavity and the filling position of the sound absorbing body by using the sound field mathematical model and the theoretical volume reduction matching optimization algorithm.

Further, the joint assembly manner of each tuning mechanism is a flange joint.

Further, the theoretical volume reduction is calculated based on the number of holes in the porous shell plate and the modified sound field mathematical model.

Further, the sound absorbing system comprises a sound absorbing cotton or a punching plate.

Further, the manner in which the tuner is fixed to the porous shell plate includes screw locking or rivet engagement.

Further, the sound field mathematical model is Correction based on which Z is the acoustic impedance; P is the sound pressure; u is the sound particle velocity; For air density; Sound speed , f is the angular frequency; L is the length of the tuning cavity.

Further, the theoretical volume reduction system utilizes versus It is calculated that 1~n is the number of each sound field, P ₁ is the sound pressure of the first sound field, P _n is the sound pressure of the nth sound field; u ₁ is the first measuring a sound field of the sound particle velocity amounts, u _n sound particle velocity of the sound field measuring the amount of n-th; S ₁ is a cross-sectional area of the sound field measuring a first amount, S _n is the n th measuring the sound field Cross-sectional area; STL is the sound penetration loss value; For the system transfer matrix, where for System operation matrix, in which the transfer matrix of the connection tube , where dn is the sounding field number of the downstream pipeline, un is the sounding field number of the pipeline upstream; Zc is the pipeline impedance of the connecting pipe, , S is the cross-sectional area of the connecting pipe; the transmission matrix of the tuner , N is the number of parallel tuner.

Further, the optimization algorithm includes a neural network algorithm, a gene algorithm, an immunology method, a particle swarm method, a traditional gradient method, a differential algorithm, an ant group algorithm or a simulated annealing algorithm.

The main object of the present invention is to provide an adjustable frequency sound reduction system which can have the following advantages without affecting the existing functions:

1. Small pressure loss: It does not affect the pressure loss of the exhaust fan system to avoid the cooling efficiency of the exhaust air due to excessive pressure loss.

2. Lightweight: Reduce the weight of the sound reduction system, modular assembly to reduce the weight of the sound reduction system, and avoid the structural weight of the sound reduction system exceeds the allowable weight of the installed floor.

3. High noise reduction: Effectively control the aerodynamic noise, which can be reduced according to the specific frequency of the actual noise to effectively suppress and reduce the low frequency noise of the exhaust fan.

Step procedure for St1~St8‧‧‧ adjustable frequency sound reduction system
1~n‧‧‧Sampling number
Sectional area of S‧‧‧ connecting pipe (supervisor)
Sa‧‧‧ cross section of tuning cavity
2a‧‧‧Sensor cavity size
L‧‧‧ Length of tuning cavity
P‧‧‧ sound pressure
u‧‧‧Sound particle velocity
OBJ‧‧‧ objective function
STL‧‧‧ Sound penetration loss value
F1~fn‧‧‧Specific frequency
10‧‧‧ Tuner
11‧‧‧Acoustic body
12‧‧‧ Tuning cavity
20‧‧‧Perforated shell
30‧‧‧Shell structure
40‧‧‧ Tuning structure

The above and other features and advantages of the present invention will become more apparent from the detailed description of exemplary embodiments.

Fig. 1 is a flow chart showing the operation flow of the adjustable frequency sound reduction system of the present invention.

2 is a schematic diagram of a single-row sound field mathematical model of the sound-reduction structure of the adjustable frequency sound reduction system of the present invention.

FIG. 3 is a schematic diagram of a multi-row sound field mathematical model of the sound-reduction structure of the adjustable frequency sound reduction system of the present invention.

Figure 4 is a schematic diagram of the theoretical volume reduction of the frequency-reducible frequency reduction system of the present invention.

Figure 5 is a schematic diagram of a tuner of a frequency-reducible frequency reduction system of the present invention.

Figure 6 is a schematic diagram of the tuning mechanism of the adjustable frequency sound reduction system of the present invention.

Figure 7 is a schematic diagram of the system assembly of the adjustable frequency sound reduction system of the present invention.

The technical features, contents, and advantages of the present invention, as well as the advantages thereof, can be understood by the inspectors, and the present invention will be described in detail with reference to the accompanying drawings, in which The subject matter is only for the purpose of illustration and description. It is not intended to be a true proportion and precise configuration after the implementation of the present invention. Therefore, the scope and configuration relationship of the attached drawings should not be interpreted or limited. First described.

Please refer to FIG. 1 , which is a flow chart of the operation flow of the adjustable frequency sound reduction system. As can be seen from Fig. 1, the calculation process is that the environmental noise St1 of the sound reduction system with the adjustable frequency is first measured, and the ambient noise is analyzed by the spectrum analysis to generate the noise source St2 of different frequencies; The sound field model correction St3 is performed according to the noise source of different frequencies; then the theoretical decrementing volume St4 of the sound reduction system is derived and evaluated according to the modified model; and the theoretical decrementing volume is used as the objective function to perform the optimization analysis operation St5, and then the tuning is obtained. The relevant dimensions of the device are designed/manufactured/assembled St6, and then the sound reduction system is assembled with St7 according to different noise frequencies, and finally the noise reduction of the on-site noise source is performed to achieve the noise control purpose St8.

The measurement of the ambient noise St1 of the sound reduction system with the adjustable frequency and the noise source St2 of the different frequencies analyzed by the spectrum analysis are known steps, and therefore will not be described. However, the sound field model correction St3 is based on the noise source of different frequencies as a formula derivation process, which will be further described in detail with the second and third figures. According to the modified model, the theoretical decrementing volume St4 of the sound reduction system and the theoretical decrementing volume as the objective function for the optimization analysis operation St5 are derived and evaluated in detail in conjunction with FIG. To obtain the dimensions of the tuner for design/manufacture/assembly St6, please refer to the descriptions in Figures 5 and 6. According to different noise frequencies, the sound reduction system assembly St7 and the on-site noise source reduction for noise control purposes are described in Figure 7.

The invention is based on the plane wave propagation theory and uses the four-turn transmission matrix to derive the analytic function of the sound transmission loss value of the sound-reduction structure. It can be known from the design principle that if the volume of the sound-reduction structure is to be reduced, the tuner can be added. With the cross-sectional area of the connecting pipe and the serial/parallel multiple tuner, the length of the tuning cavity and the microstructure of the sound absorbing material can be adjusted if the audio frequency is adjusted.


Please refer to FIG. 2 , which is a schematic diagram of a single-row sound field mathematical model of the sound-reduction structure of the adjustable frequency sound reduction system of the present invention. It is known from the above design criteria that the second figure is based on the principle of increasing the number of parallels of the tuner and the connecting pipe (supervisor) to increase the volume reduction of the damping structure. The sound reduction structure is a single-row connecting tube (supervisor) with 4 tuner as an example and 6 measuring sound fields are set, among which the sound field mathematical model of the sound-reduction structure is used. Based on which Z is the acoustic impedance; P is the sound pressure; u is the sound particle velocity; For air density; Sound speed , f is the frequency; L is the length of the tuning cavity. When the acoustic impedance Z of the equivalent sound field is known as the target preset value in the mathematical model of the sound field, the length L of the tuning cavity is the correlation function coefficient of the frequency f, and the specific frequency f is correspondingly The length L of the particular tuning cavity.
The relevant formula is derived as follows:

The sound field mathematical model of the single-row 4 tuner is constructed by the acoustic impedance formula (formula 1), the four-turn transfer matrix formula (formula 2) and the sound penetration loss formula (formula 3).
(Formula 1)
(Formula 2)
(Formula 3)
1~n is the number of each sound field, P ₁ is the sound pressure of the first measurement sound field, P _n is the sound pressure of the nth measurement sound field; u ₁ is the first measurement sound field of the sound particle velocity, u _n sound particle velocity of the sound field measuring the amount of n-th; S ₁ is a cross-sectional area of the sound field measuring a first amount, S _n sectional area of the sound field measuring the amount of n-th; the STL For the sound penetration loss value.

However, the purpose of the sound reduction system of the present invention is that the pressure loss at the inlet and outlet of the sound reduction device is extremely small, so it is assumed that there is no pressure loss: P ₁ = P ₆ , and the relevant parameters are brought into (Formula 1) (Formula 2) (Formula 3) Available later




When the correlation coefficient is brought into the operation, the analytical solution of the length L of the tuning cavity and the size 2a of the tuning cavity can be known.

Please refer to FIG. 3 , which is a schematic diagram of a multi-row sound field mathematical model of the sound reduction structure of the adjustable frequency sound reduction system of the present invention. The third figure is based on the design criteria of connecting a plurality of tuner in series, and the sound reduction structure in which four tuners are arranged in each column and connected in series to three columns is taken as an example, and eight measurement sound fields are set. In the same way, the relevant parameters are brought into (Formula 2) (Formula 3).



However, the series sound-absorbing structure is interconnected by a connecting pipe and a tuner, so the system transmission matrix is
For the system transfer matrix, where for System operation matrix, in which the transfer matrix of the connection tube , where dn is the sounding field number of the downstream pipeline, un is the sounding field number of the pipeline upstream; Zc is the pipeline impedance of the connecting pipe, , S is the cross-sectional area of the connecting pipe; similarly, the transmission matrix of the tuner is , N is the number of parallel tuner.
When the correlation coefficient is brought into the calculation, the analytical solution of the length (L1, L2, L3) of the tuning cavity and the size (2a1, 2a2, 2a3) of the tuning cavity can be known.

Please refer to FIG. 4, which is a schematic diagram of the theoretical volume reduction of the frequency-reducible frequency reduction system of the present invention. As can be seen from Fig. 4, for a wideband noise having multiple tones (f1, f2, f3... to fn), a plurality of tunings with a specific single frequency (f1, f2, f3... to fn) can be designed. The sound penetration loss value of the integrated tuner can be concatenated as an envelope type. Therefore, the envelope curve of Fig. 4 is set as the objective function OBJ, and the theoretical deduction of the system is used and the optimization is utilized. The algorithm, in the case of the maximum volume reduction, to find the relevant size of each tuning mechanism. However, the optimization algorithm includes a neural network algorithm, a gene algorithm, an immunology method, a particle swarm method, a traditional gradient method, a differential algorithm, an ant group algorithm or a simulated annealing algorithm.

Please refer to FIG. 5, which is a schematic diagram of a tuner of a frequency-reducible frequency reduction system of the present invention. As can be seen from Fig. 5, the tuner 10 is composed of the sound absorbing body 11 and the tuning cavity 12, and the sound absorbing body 11 is filled in the tuning cavity 12, by adjusting the filling position of the sound absorbing body 11 to respectively The corresponding plurality of specific frequencies are eliminated, and the size of the tuning cavity 12 and the filling position of the sound absorbing body 11 are calculated by the above-described mathematical model of the sound field. The sound absorbing body 11 includes various sound absorbing materials such as sound absorbing cotton or punching plates. The perforated shell 20 is a perforated shell plate having a plurality of holes to hold a plurality of tuner 10, and the tuner 10 and the perforated shell 20 are secured in a manner that includes screw locking or rivet engagement.

Please refer to FIG. 6 , which is a schematic diagram of the tuning mechanism of the adjustable frequency sound reduction system of the present invention. As can be seen from Fig. 6, the tuning mechanism 40 is comprised of a tuner 10, a perforated casing 20, and an outer casing structure 30. A plurality of tuners 10 are embedded in the holes of the porous shell plate 20, and the porous shell plates of the plurality of tuners 10 are assembled by adjusting the filling position and the pore structure of the sound absorbing body 11 to absorb different ranges of noise. 20 is fixed in the outer casing structure 30 to form a tuning mechanism 40.

Please refer to FIG. 7 , which is a schematic diagram of the system assembly of the adjustable frequency sound reduction system of the present invention. The noise source spectrum according to different frequencies is designed by the method proposed by the present invention, and the modular design, manufacturing and assembly are used to save process cost, and a plurality of tuning mechanisms 40 can be disassembled or assembled according to actual environmental requirements, according to a plurality of specific noises. The frequency is correspondingly assembled to the tuning mechanism 40 of a specific frequency, wherein the connection and assembly manners of the respective tuning mechanisms 40 are flange joints, and can be freely assembled and disassembled according to requirements, so as to achieve the purpose of light weight, small pressure loss and high sound reduction.

Looking at the above, it can be seen that the present invention has achieved the desired effect under the prior art, and is not familiar to those skilled in the art. Moreover, the present invention has not been disclosed before the application, and it has Progressive and practical, it has already met the requirements for patent application, and has filed a patent application according to law. You are requested to approve the application for this invention patent to encourage creation.

The embodiments described above are merely illustrative of the technical spirit and the features of the present invention, and the objects of the present invention can be understood by those skilled in the art, and the scope of the present invention cannot be limited thereto. That is, the equivalent variations or modifications made by the spirit of the present invention should still be included in the scope of the present invention.

Step procedure for St1~St8‧‧‧ adjustable frequency sound reduction system

Claims (8)

An adjustable frequency sound reduction system for separately performing noise reduction processing on noise of different frequencies, the adjustable frequency sound reduction system comprising a detachable assembled complex array tuning mechanism, wherein the complex array tuning mechanism respectively corresponds to a plurality of specific The noise frequency, wherein each of the complex array tuning mechanisms comprises: a plurality of tuner, each of the plurality of tuners comprising a tuning cavity and a sound absorbing body, wherein the sound absorbing body is filled in the tuning cavity, Adjusting the filling position of the sound absorbing body to respectively eliminate the corresponding plurality of specific frequencies; a porous shell plate for fixing the plurality of tuners; and a casing structure for fixing the porous shell plate and the plurality of tunings The complex array tuning mechanism calculates a size of the tuning cavity and a filling position of the sound absorbing body by using a sound field mathematical model, a theoretical volume reduction, and an optimization algorithm. The sound-absorbing system of the adjustable frequency according to the first aspect of the patent application, wherein the joint assembly mode of the complex array tuning mechanism is a flange joint. The sound reduction system of the adjustable frequency according to claim 1, wherein the theoretical volume reduction is calculated according to the number of holes of the porous shell plate to correct the mathematical model of the sound field. The adjustable frequency sound reduction system of claim 1, wherein the sound absorbing system comprises at least one sound absorbing cotton or at least one punching plate. The adjustable frequency sound attenuation system of claim 1, wherein the tuner and the porous shell are fixed in a manner that includes screw locking or rivet engagement. An adjustable frequency sound reduction system as described in claim 1, wherein the sound field mathematical model is Correction based on which Z is the acoustic impedance; P is the sound pressure; u is the sound particle velocity; For air density; Sound speed , f is the frequency; L is the length of the tuning cavity. An adjustable frequency sound reduction system as described in claim 1 wherein the theoretical volume reduction system utilizes versus It is calculated that 1~n is the number of each sound field, P ₁ is the sound pressure of the first sound field, P _n is the sound pressure of the nth sound field; u ₁ is the first measuring a sound field of the sound particle velocity amounts, u _n sound particle velocity of the sound field measuring the amount of n-th; S ₁ is a cross-sectional area of the sound field measuring a first amount, S _n is the n th measuring the sound field Cross-sectional area; STL is the sound penetration loss value; For the system transfer matrix, where for System operation matrix, in which the transfer matrix of the connection tube , where dn is the sounding field number of the downstream pipeline, un is the sounding field number of the pipeline upstream; Zc is the pipeline impedance of the connecting pipe, , S is the cross-sectional area of the connecting pipe; the transmission matrix of the tuner , N is the number of parallel tuner. The adjustable frequency sound reduction system according to claim 1, wherein the optimization algorithm comprises a neural network algorithm, a gene algorithm, an immunology method, a particle swarm method, a traditional gradient method, a differential calculus Method, ant colony algorithm or simulated annealing algorithm.