Study on the influence of different characterization characteristics on intelligent toilet noise test

With the improvement of the living standards of urban and rural residents, the popularity of intelligent toilets is increasing year by year. The noise issue of intelligent toilets has become one of the main complaints from consumers. The noise of intelligent toilets mainly comes from three functions: cleaning, blowing, and flushing. Due to the lag in research on relevant noise measurement theories and technologies, there is currently a gap in the standards for supporting testing methods. This article adopts step-by-step measurement and overall measurement methods and selects F gear, S gear, and I gear to measure the noise of the tested samples separately. The measurement results of different methods are measured according to L50 and L10, providing a scientific basis for evaluating the noise-influencing factors of intelligent toilet products.


Introduction
With the general improvement of urban and rural people's living standards, intelligent, functional diversification of equipment has become a civil building toilet interior decoration's new trend, intelligent household industry chain is included as one of the ten iconic industry chains during the 14th Five Year period in Zhejiang, and the intelligent toilet, as the core component of intelligent household industry chain, its penetration rate is increasing year by year.In the narrow toilet, in addition to the inherent fluid noise, water hammer noise, and the noise generated by various motors, controllers and other electrical system, different types of noise makes indoor noise pollution further intensified.According to the national mandatory standard GB 50096-2011 [1] "Design code for residential buildings", at least three sanitary ware toilets, baths and washers should be installed in the toilet, and the indoor area is not less than 3 m 2 ; the allowable limit of daytime noise level is 50 dB.The recommended standard GB/T 23131-2019 [2] "Household and similar electrical toilets" constrained by indoor noise monitoring requirements, specifies "sound power level of the noise from low to high A, B, C, D, the maximum limit is not greater than 68 dB (A) for electrical toilets", but is limited by the lag in research on theory and technology of correlated noise measurement.The supporting test method standard is still blank, making the above standard limit requirements, experimental verification without standard.

Test content
The noise of intelligent toilet seats mainly comes from the three functions of cleaning, blowing and washing.The noise of different functions depends on the design of the current products in the market, consumers can independently use three functions to produce single noise in the actual use process; they also can continuously use three functions of the product, making the cleaning process with brushing or blowing with brushing, and different functions produce superimposed noise to each other.In order to evaluate the noise influencing factors of intelligent toilet products more scientifically, this test adopts the A weight method through the step-by-step measurement and overall measurement method, and F, S and I pulse positions are selected to measure the noise measurement respectively, and evaluates the measurement results of different methods according to L50 and L10 [3] .

Trial scheme
The intelligent toilet noise test platform consists of a semi-anechoic room, constant temperature and pressure water tank, acoustic measurement and analysis equipment, flow meter, thermometer, drainage system, etc. Fig. 1 shows the noise test block diagram.During the test, the intelligent toilet is installed in the semi-anechoic room, the drainage outlet is closely attached to the ground and aligned with the preset drainage system, and sound insulation measures such as rubber pads are used to ensure that there is no interference noise between the sample and the ground during the test.The constant temperature and pressure water tank is placed outside the semi-anechoic room, and the water supplied to the intelligent toilet is through the preset pipeline, the water pressure and water temperature is measured at the water inlet.

Sample selection and working conditions
A total of 14 samples are selected for this test, seven of them are pressure type and the others are gravity type.Fig. 2 shows pressure type and gravity type structure diagram [4] .Because the different water pressure and water temperature have a great impact on the noise of the pressure structure, in order to make an effective comparison, the water pressure in this test is (0.35 ± 0.05) MPa of static pressure and the water temperature is (15 ± 1)℃ [5] .In terms of water supply, the water tank is filled with water in normal condition; the pressure intelligent toilet keeps connecting to the water supply pipe.The test measures the noise independently for a cleaning cycle, two minutes of warm air blowing, and a brushing cycle.

Confirmation of measuring surface
According to the installation position of the intelligent toilet, considering that the noise has certain directivity, the measuring surface is measured by the hemisphere method with a relatively large measurement distance [6] , The coordinates of the measuring points are shown in Table 1.The measurement radius is r ≥ 2 d 0 , and not less than 1 meter, not more than 16 meters.According to the value of the datum d 0 , the surface radius of the measuring hemisphere is 2 meters, and the measured area is S=2πr 2 =25.12m 2 .

Data processing and analysis
In accordance with the 1.3, 1 # -14 # sound source samples of intelligent toilets are installed by using the array of fixed microphone positions distributed on the hemisphere measurement surface to measure and locate the microphone position using a steel tape measure and a tripod according to Table 1 and Fig. 3, in order to ensure that the orientation of the microphone is the same as the incident angle of the calibrated sound wave and perpendicular to the measurement surface.In the semi-anechoic room, the tester wearing clothes with unobvious sound absorption characteristics is responsible for starting various functions of the intelligent toilet.

Water flushing noise analysis
Starting the flushing mode [7] for the sound source samples 1 # to 14 # of the intelligent toilet, the relevant measurement results are shown in Table 2, Fig. 4, and Fig. 5.According to the bar chart of flushing noise in Fig. 4 and Fig. 5, the flushing noise of 1 # -7 # sound source samples of the intelligent toilet with pressure type is higher than 8 # -14 # sound source samples of the intelligent toilet with gravity type.By exploring the noise curves of two structural flushing methods, it was found that the flushing cycle of the pressure-type intelligent toilet is about 20 seconds.The curve is shown in Fig. 6, and there is a fluctuation in the noise throughout the flushing cycle from skirt flushing to spray siphoning, water replenishment; The flushing cycle of the gravity intelligent toilet is about 40 seconds, as shown in Fig. 7.The high noise state only lasts for less than 10 seconds in the initial flushing stage, and 30 seconds is in water tank replenishment state with the relatively low noise.Therefore, there is a significant difference in the calculation results of L WA (50) and L WA (10) for both pressure and gravity products.The impact of different gears is analyzed and compared to the flushing noise.The sampling period of F gear is 125 ms, and its curve is sharp with significant changes in flushing noise within 1 second; The sampling period of S gear is 1000 ms, which means sampling a point in 1s, and the curve is relatively flat.Due to the complex changes in water flushing noise, which consists of simple noise, solid noise [8] , turbulence noise, etc., when using S gear testing, there is a problem where the collected data is not enough to reflect the true state of the product.Therefore, the data from the S gear weighting test on 8 # -14 # sound source samples has a significant deviation from other time weighting tests, and the measurement accuracy is not high.

Blowing noise analysis
Starting the blowing mode for the sound source samples 1 # to 14 # , and the relevant measurement results are shown in Table 3, Fig. 8, and Fig. 9.For different intelligent toilet products, the distribution of blowing noise is (45-62) dB.The blowing noise is related to the speed of the fan impeller, the shape and number of blades, the relative speed, etc [9] .However, through analysis, it was found that the variation of blowing noise is relatively small throughout the entire cycle, as shown in Fig. 10.The difference in statistical data between L WA (50) and L WA (10) is not significant, and the difference in measurement data between F, I, and S ranges is also not significant.

Cleaning noise analysis
Starting the cleaning mode for the sound source samples 1 # to 14 # , and the relevant measurement results are shown in Table 4, Fig. 11, and Fig. 12.    From the bar charts of Fig. 11 and Fig. 12 of cleaning noise, it was found that there were significant differences in the measurement results of cleaning noise among the three different time weighting methods of F, I, and S, as shown in Fig. 13.The cleaning noise of intelligent toilets consists of water jet noise [10] , spray bar motor stretching noise, air pump noise, etc., and there are significant differences in the cleaning functions of different enterprises in program design, spray bar structure, working principle, etc., resulting in inconsistent testing results at different sampling frequencies.

Conclusion
Based on the results and discussions presented above, the conclusions are obtained as below: (1) It is proven that there are significant differences in the noise sources of the three functions of cleaning, blowing, and flushing for intelligent toilets.Choosing different cumulative percentage sound power level characterization methods has little impact on blowing noise, but there are significant differences in cleaning and flushing noise.Therefore, it is necessary to specify this calculation method.
(2) Due to the relatively long blowing time, and even some products have blowing time exceeding 5 minutes, S-time weighting can be used to test the noise of the entire blowing cycle of the intelligent toilet, which is helpful for data collection and analysis; Due to the complexity of the cleaning function in terms of structural design, function, etc., it is recommended to select the time-weighted F gear for testing the cleaning noise to improve the accuracy of the test; (3) This paper considers the impact of environmental conditions, personnel conditions, water temperature and pressure, and different flushing structures on the test results when measuring the noise of intelligent toilets.However, due to factors such as sample quantity and measurement conditions, the noise of cleaning, blowing, and flushing is measured independently during this measurement process.However, in actual use, different types and time series of noise overlap and interfere with each other.Therefore, it is urgent to further standardize and improve the testing technology for the overall noise of toilets.
(4) According to the measurement data of 14 samples in this paper, the flushing noise of the pressure-type intelligent toilet is significantly higher than that of the gravity-type product.There are significant differences in the blowing noise and cleaning noise data of different products.The test results reflect the development level of the current intelligent toilet industry in China.There is still much room for improvement in the silent technology of pressure products, the noise reduction technology of products with large blowing air volume and Great Purge flow.

Figure 1 .
Figure 1.The noise test block diagram.

Figure 2 .
Figure 2. Pressure type structure diagram & gravity type structure diagram.

Figure 6 .
Figure 6.Flushing noise curve of the intelligent toilet with flushing valve under three time-weighted conditions.

Figure 7 .
Figure 7. Flushing noise curve of the intelligent toilet with water tank under three time-weighted conditions.

Figure 10 .
Figure 10.Blowing noise curve of intelligent toilet under three time-weighted conditions.

Figure 13 .
Figure 13.Cleaning noise curve of intelligent toilet under three time-weighted conditions.

Table 2 .
Sound power level data of flushing.

Table 3 .
Sound power level data of blowing noise.

Table 4 .
Sound power level data of cleaning noise.