Introduction
People attach great importance to the quality and safety of domestic water. Water purifiers can effectively purify water resources, so the market demand for water purifiers is constantly increasing. However, noise often occurs in the practical application of water purifiers. In water purifier equipment, the noise sources of the booster pump are diverse, including vibrations from the water pump, valves, and pipelines. According to the characteristics of noise formation, corresponding noise reduction technologies need to be applied to effectively solve the noise problem.

1 Noise Analysis of Booster Pumps for Water Purifiers

1.1 Noise Test Analysis

1.1.1 Test Conditions and Procedures

This test and analysis of the noise of booster pumps for water purifiers will select reverse osmosis water purifier equipment. This type of water purifier structure includes composite filter elements, reverse osmosis filter elements, self-priming booster pumps, external water tanks, etc. During operation, the equipment cannot be in direct contact with tap water; tap water needs to be placed in the water tank first. Then, the booster pump with self-priming function is connected to the composite filter element, and the composite filter element is connected to the reverse osmosis filter element to form a complete water production system of the water purifier. When analyzing the operating noise of the water purifier, it is necessary to create test conditions: the temperature of the test environment should be controlled at 25 degrees, the humidity at 40%, and the test space should be a standard anechoic chamber.

Before conducting the test, the operating parameters of the booster pump should be adjusted reasonably. When the inlet water pressure is 0, the operating pressure of the booster pump should not exceed 0.5Mpa, and the water flow during operation should not be less than 550mL per minute. Therefore, during the test, the inlet water pressure needs to be adjusted to 0, then the booster pump is connected to the raw water storage structure and the filter element structure. First, test the pure water and wastewater flow under the operation of the equipment. When the flow reaches the corresponding qualified standard, observe the operating state of the water purifier. After reaching a relatively stable level, the noise test can start.

1.1.2 Application of Test Methods

The reasonable application of test methods directly affects the reliability of noise test data. The selection of test methods needs to refer to the relevant regulations of the general requirements for noise test methods of household appliances to ensure the applicability of the test methods. This noise test research will adopt the ten-point method, using A-weighting for measurement, and the evaluation quantity is set as sound power. With this measurement method, the measurement surface structure is a hemispherical surface, and ten measurement points are set on the measurement surface structure. For the measurement surface, the diameter of the hemisphere needs to be reasonably controlled. If the size of the measuring instrument is small, the diameter of the surface hemisphere should be set to 2m, and the radius to 1m. This research uses this diameter structure for measurement activities. During the test, a measuring instrument needs to be used to ensure the accuracy of the measured values. Before the official measurement, the measuring instrument needs to be placed at the designed measurement point and installed. During the whole machine test, it is necessary to focus on observing the position of the whole machine at any time to ensure its rationality. Usually, the position of the whole machine needs to be at the center platform of the hemisphere. The sound power values obtained from each measurement point are calculated in accordance with the relevant provisions in the standards GB/T3767–1996 and GB6882–1986.

1.2 Analysis of Noise Data

For the analysis of noise measurement data, five booster pump devices from the same production batch were selected. The input voltage and current parameters of the booster pump were set to standard conditions: the input voltage was DC24V, the working current was controlled within the range of 0.5-0.72A, the flow parameter per minute under working conditions was greater than or equal to 550mL, and the motor speed parameter was greater than 800rpm but not exceeding 960rpm. During the test, the inlet water pressure was adjusted to 0, and the pump output pressure was set to 0.5Mpa. After the noise test of a single pump was completed, the five booster pumps were placed in the corresponding whole machine equipment. During the installation of the booster pump, focus on the metal supports and the sheet metal parts of the whole machine, and connect them with shock-absorbing pads and screws. After the installation of the whole machine, a trial operation was carried out first to confirm the actual inlet water pressure. When the operating state of the whole machine reached a stable level, the ten-point method was used to measure and collect noise data. The corresponding noise data obtained are shown in Table 1.

Table 1 Noise measurement data of five groups of water purifier booster pumps

A total of five booster pumps' operating noise were measured. It can be found from the noise measurement values of groups 1-5 that the noise level of the whole machine is higher than that of a single pump. The booster pump is the main noise-generating structure in the water purifier. The reasons for the higher noise level of the whole machine are, on the one hand, that the booster pump itself has relatively large noise, which gradually increases during sound propagation. On the other hand, there is a resonance effect between the whole machine and the booster pump during operation, which intensifies the noise level. Therefore, it is necessary to adopt corresponding noise reduction technologies to improve the noise of the water purifier.

2 Analysis of Noise Reduction Technology for Booster Pumps of Water Purifiers

When reducing the noise of the booster pump for water purifiers, there are mainly two approaches: one is to control the operation of the source structure that generates noise, and the other is to control the propagation of noise. The booster pump is the main source of noise in the water purifier, and the resonance generated by the joint operation of the whole machine and the booster pump is also the main body of noise formation. Noise reduction of the booster pump can be achieved by optimizing the motor operating speed and the structural design of the water purifier. The following is a specific analysis of the optimal application of noise reduction technology.

2.1 Optimization of Motor Speed

The booster pump for water purifiers will generate relatively large noise during operation, and the main reason for the noise is the rotation of the motor. During the operation of the water purifier, the motor drives the eccentric wheel through rotation to perform reciprocating motion, so that the water purifier can perform its drainage function. Noise is generated during this rotation and driving process. To reduce the noise of the booster pump, it can be achieved by reducing the rotation speed of the motor. When the speed of the motor decreases, the volume chamber and eccentric wheel angle of the booster pump can be adjusted, making the motor rotation speed 300rmp different from the original pump rotation speed. Then, the noise values of the booster pump in the operation of a single pump and the whole machine can be measured and determined. Similarly, during the measurement, the inlet water pressure needs to be set to 0, and the output pressure of the equipment operation to 0.5Mpa, then measure and analyze the operating noise of five groups of booster pumps. The specific noise measurement values of each group of booster pumps are shown in Table 2.

By comparing the noise values measured in Table 2 with those in Table 1, it can be clearly observed that the noise level of each group of booster pumps has been significantly reduced, which proves that noise reduction can be achieved by optimizing the motor speed. Moreover, by comparing the noise measurement values before and after optimization, it can be found that the noise reduction effect of the whole machine is better than that of a single pump. Thus, it can be determined that after the noise level of a single pump decreases, the noise level generated by resonance during the operation of the whole machine will also decrease synchronously, and the operating state of the whole machine has been optimized accordingly.

When the speed of a single pump decreases, the current level during the operation of the equipment also decreases to 0.56A. Through calculation, the power value after the change can be obtained, which is lower than that in the original operating state. Therefore, the application of this noise reduction technology is feasible, which can reduce noise and the operating power of the booster pump, while ensuring sufficient water supply for the water purifier. After the motor speed is reduced, the average noise level of the whole machine is maintained at 52dB (A), and there is still room for reduction. Therefore, it is necessary to combine other noise reduction optimization measures to further strengthen noise reduction.

2.2 Optimization of the Booster Pump Structure

Materials with shock-absorbing properties can be used in the structural design of water purifiers. For example, silicone materials can well isolate vibration effects and have good sound insulation functions, which can alleviate vibration and sound propagation. Silicone materials can be applied to the structural design of water purifiers to improve the noise reduction level. Silicone material with a Shore hardness of 50 can be made into a silicone sleeve to fix the booster pump, or a noise reduction box combined with silicone can be used to fix the booster pump. In this way, the booster pump can be placed in the bracket structure in a suspended form, and there will be no vibration transmission during the operation of the water purifier. After optimizing the structure of the booster pump, install it in the corresponding water purifier, then use the same noise measurement method to obtain and collect the noise values of the equipment operation. The specific noise measurement after the optimization of the booster pump structure is shown in Table 3.

By comparing the values in Table 3 with those in Table 2, it can be seen that the application of silicone materials to optimize the structure of the booster pump can effectively enhance the noise reduction effect, which is of great help to the noise reduction of the whole water purifier. The average noise reduction range is about 2dB (A). However, in the application of different silicone materials, the actual noise reduction effects are different. Among different silicone materials, silicone with lower hardness can be selected to reduce the resonance caused by the booster pump, thereby reducing the noise of the whole machine. In this process, it is also necessary to comprehensively consider the influence of factors such as the silicone production process, structural stability, and reliability [3]. During the optimization of the booster pump structure, the noise reduction box device can absorb the noise generated during the operation of the equipment, eliminate part of the noise, and convert the noise energy into heat energy, thereby further optimizing the noise reduction quality of the water purifier.

2.3 Application of Control Software Technology

The development level of modern control technology is gradually improving. In the structural design of water purifiers, control software technology can be applied to achieve noise reduction. It mainly adjusts and controls the pulse width parameters by using control software on the basis of ensuring the standardized and efficient operation of the water purifier device, so as to optimize the operating parameters such as the input voltage of the motor and the motor speed, thereby achieving the noise reduction optimization effect of the booster pump. The impulse resistance width of the booster pump has a direct impact on the operating state of the equipment. It can be output through a digital processor to control the operation of the analog circuit, obtain pulse values with consistent amplitude at the output end, and adjust the pulse width according to corresponding rules, so as to achieve the noise reduction optimization effect.

2.3 Application of Control Software Technology

The development level of modern control technology is gradually improving. In the structural design of water purifiers, control software technology can be applied to achieve noise reduction. It mainly adjusts and controls the pulse width parameters by using control software on the basis of ensuring the standardized and efficient operation of the water purifier device, so as to optimize the operating parameters such as the input voltage of the motor and the motor speed, thereby achieving the noise reduction optimization effect of the booster pump. The impulse resistance width of the booster pump has a direct impact on the operating state of the equipment. It can be output through a digital processor to control the operation of the analog circuit, obtain pulse values with consistent amplitude at the output end, and adjust the pulse width according to corresponding rules, so as to achieve the noise reduction optimization effect.