A test method for the noise reduction coefficient of a sound barrier material

Abstract

This invention discloses a method for testing the noise reduction coefficient of a sound barrier material, comprising the following steps: placing a plate-shaped test specimen made of the noise reduction material into a reverberation chamber; measuring the sound absorption coefficient α at different frequency bands. s A sound absorption coefficient curve was plotted to determine the maximum sound absorption coefficient α of the noise reduction material. max Determine half of the maximum sound absorption coefficient α based on the sound absorption coefficient curve. max The minimum frequency f corresponding to / 2 min and maximum frequency f max According to f min and f max Determine the frequency band Δf = [f min ,f max According to the traffic noise frequency band Δf T And determine the traffic noise bandwidth Card(Δf) T Determine the effective sound absorption frequency band of the material Δf∩Δf T And determine the effective sound absorption bandwidth Card(Δf∩Δf) T This method allows for the determination of the noise reduction coefficient ε of the material in traffic noise applications. The method for testing the noise reduction coefficient of sound barrier materials in this invention has advantages such as the ability to analyze and evaluate the noise reduction performance of sound barriers through noise reduction coefficient evaluation indicators, and accurately reflecting the sound absorption characteristics and effects of the materials.

Description

Technical Field

[0001] This invention relates to a method for testing the performance of noise reduction materials, and more particularly to a method for testing the noise reduction coefficient of a sound barrier material. Background Technology

[0002] Noise reduction materials are materials that can reduce or eliminate sound propagation. They are widely used in various fields such as construction, transportation, and audio equipment to reduce the impact of noise on the environment and people. These materials achieve their noise reduction effect through different mechanisms, including sound absorption, reflection, and blocking.

[0003] Sound barriers are primarily used for noise reduction in highways, expressways, elevated composite roads, and other noise sources. In recent years, sound barriers have been widely applied on highways and railways as an effective traffic noise reduction measure. In sound barrier design, the sound absorption coefficient of the material is measured according to standards such as "Measurement of Sound Absorption Coefficient and Acoustic Impedance in Acoustic Impedance Tubes Part 1: Standing Wave Ratio Method" (GB / T 18696.1-2004), "Measurement of Sound Absorption Coefficient and Acoustic Impedance in Acoustic Impedance Tubes Part 2: Transfer Function Method" (GB / T 18696.2-2002), or "Measurement of Sound Absorption in Reverberation Chambers" (GB / T 20247-2006), thereby confirming the noise reduction performance of the material. Among these standards, the Noise Reduction Coefficient (NRC) is an important indicator for evaluating the noise reduction performance of sound barriers and is often used to quickly compare and screen sound barrier materials with strong acoustic performance.

[0004] With changes in vehicle type, speed, and road conditions, traffic noise is gradually shifting towards mid-to-high frequencies. Traditional sound barriers are no longer perfectly suited to the characteristics of current traffic noise, resulting in poor noise reduction. Furthermore, the traditional NRC (Noise Reduction Ratio) evaluation metric only weights and averages the sound absorption coefficients at four frequency bands: 250Hz, 500Hz, 1000Hz, and 2000Hz, failing to accurately reflect the noise reduction effect of the barrier material in actual traffic conditions.

[0005] Therefore, the existing noise reduction performance index (NRC) of sound barriers is obtained through traditional noise reduction material analysis and measurement methods, which cannot accurately reflect the true performance of sound barriers in traffic noise control and cannot guide the design of sound barriers. Therefore, it is urgent to study a testing method suitable for the performance parameters of noise reduction materials under modern traffic conditions to solve this technical problem. Summary of the Invention

[0006] To avoid the shortcomings of the existing technology, the present invention provides a method for testing the noise reduction coefficient of sound barrier materials, so as to determine the sound absorption coefficient of the sound barrier manufacturing material at different frequencies and accurately reflect the sound absorption characteristics of the material.

[0007] The present invention adopts the following technical solution to solve the technical problem.

[0008] The present invention provides a method for testing the noise reduction coefficient of a sound barrier material, comprising the following steps:

[0009] Step 1: The noise reduction material used to manufacture the sound barrier is made into a plate-shaped test piece;

[0010] Step 2: Using the reverberation chamber method, measure the sound absorption coefficient α of the noise reduction material in different frequency bands of 100Hz≤f≤5000Hz. s And plot the sound absorption coefficient curve;

[0011] Step 3: Based on the sound absorption coefficient α s And the sound absorption coefficient curve, to determine the maximum sound absorption coefficient α of the noise reduction material. max ;

[0012] Step 4: Determine half of the maximum sound absorption coefficient α based on the sound absorption coefficient curve. max The minimum frequency f corresponding to / 2 min and maximum frequency f max ;

[0013] Step 5: Based on the minimum frequency f min and maximum frequency f max The sound absorption coefficient was determined to be α. max / 2 corresponds to the frequency band Δf = [f min ,f max ];

[0014] Step 6: Based on the traffic noise frequency band Δf T Determine the traffic noise bandwidth Card(Δf) T );

[0015] Step 7: Based on Δf and Δf T Calculate the effective sound absorption frequency band Δf∩Δf of the noise reduction material. T Determine the effective sound absorption bandwidth Card(Δf∩Δf) T );

[0016] Step 8: Calculate the noise reduction coefficient ε of the noise reduction material in traffic roads.

[0017] The method for testing the noise reduction coefficient of a sound barrier material according to the present invention is also characterized by:

[0018] In specific implementation, in step 2, when no plate-shaped test piece is placed in the reverberation chamber, the calculation formula for the sound absorption A1 of the open reverberation chamber is as follows:

[0019]

[0020] In formula (1), V is the volume of the open reverberation chamber, c1 is the speed of sound in the air in the open reverberation chamber, T1 is the reverberation time of the open reverberation chamber, and m1 is the sound intensity attenuation coefficient under the open reverberation chamber condition.

[0021] After placing the plate-shaped test specimen, the formula for calculating the sound absorption A2 of the reverberation chamber is as follows:

[0022]

[0023] In formula (2), c2 is the speed of sound in the air in the reverberation chamber after the plate-shaped test piece is placed; T2 is the reverberation time of the reverberation chamber after the plate-shaped test piece is placed; and m2 is the sound intensity attenuation coefficient under the reverberation chamber conditions after the plate-shaped test piece is placed.

[0024] In specific implementation, in step 2, the sound absorption A of the plate-shaped test piece T The calculation formula is:

[0025]

[0026] The sound absorption coefficient α s The calculation formula is:

[0027]

[0028] In formula (4), S is the area of ​​the plate-shaped test piece.

[0029] In specific implementation, in step 4, if α max The minimum frequency f corresponding to / 2 min and maximum frequency f max If the frequency is not within the range [100, 5000], then the minimum frequency f is taken. min =100Hz or maximum frequency f max =5000Hz.

[0030] In specific implementation, in step 5, based on the traffic noise frequency band Δf T Traffic noise frequency band Δf T The bandwidth is Card(Δf) T ).

[0031] In specific implementation, the formula for calculating the noise reduction coefficient ε is as follows:

[0032]

[0033] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0034] This invention discloses a method for testing the noise reduction coefficient of a sound barrier material, comprising the following steps: fabricating the noise reduction material into a plate-shaped test specimen; placing the plate-shaped test specimen in a reverberation chamber and measuring the sound absorption coefficient α at different frequency bands. s A sound absorption coefficient curve was plotted to determine the maximum sound absorption coefficient α of the noise reduction material. max Determine the two absorption coefficients α that account for half of the maximum sound absorption coefficient based on the sound absorption coefficient curve. max / 2, based on two α max / 2 Determine the frequency band Δf corresponding to the center frequency of the corresponding 1 / 3 octave band. If α max The center frequency of the 1 / 3 octave band corresponding to / 2 exceeds [100, 5000] Hz. Based on actual test results, the cutoff frequency of 100 Hz or 5000 Hz is taken, according to the traffic noise frequency band Δf. T And determine the traffic noise bandwidth Card(Δf) T Determine the effective sound absorption frequency band of the material Δf∩Δf T And determine the effective sound absorption bandwidth Card(Δf∩Δf) T To determine the noise reduction coefficient ε of the material in traffic noise applications.

[0035] The method for testing the noise reduction coefficient of sound barrier materials of the present invention has the advantages of being able to analyze and evaluate the noise reduction performance of sound barriers through the noise reduction coefficient of noise reduction materials, and accurately reflecting the sound absorption characteristics and effects of materials. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for testing the noise reduction coefficient of a sound barrier material according to the present invention.

[0037] Figure 2 This is a schematic diagram of the reverberation chamber method for measuring the sound absorption coefficient of noise reduction materials according to the present invention.

[0038] Figure 3 This is a field test diagram of the sound absorption coefficient of the granular rock slab in Embodiment 1 of the present invention.

[0039] Figure 4 This is a sound absorption coefficient curve of Embodiment 1 of the present invention.

[0040] Figure 5 This is a field test diagram of the sound absorption coefficient of the double-coated metal plate in Embodiment 2 of the present invention.

[0041] Figure 6 This is a sound absorption coefficient curve of Embodiment 2 of the present invention. Detailed Implementation

[0042] See Figures 1-6 The present invention provides a method for testing the noise reduction coefficient of a sound barrier material, comprising the following steps:

[0043] Step 1: The noise reduction material used to manufacture the sound barrier is made into a plate-shaped test piece;

[0044] Step 2: Using the reverberation chamber method, measure the sound absorption coefficient α of the noise reduction material in different frequency bands of 100Hz≤f≤5000Hz. s And plot the sound absorption coefficient curve;

[0045] When 100Hz≤f≤5000Hz, the center frequency f corresponding to 1 / 3 octave band includes 100Hz, 125Hz, 160Hz, 200Hz, 250Hz, 315Hz, 400Hz, 500Hz, 630Hz, 800Hz, 1000Hz, 1250Hz, 1600Hz, 2000Hz, 2500Hz, 3150Hz, 4000Hz, and 5000Hz.

[0046] Step 3: Based on the sound absorption coefficient α s And the sound absorption coefficient curve, to determine the maximum sound absorption coefficient α of the noise reduction material. max ;

[0047] Step 4: Determine half of the maximum sound absorption coefficient α based on the sound absorption coefficient curve. max The minimum frequency f corresponding to / 2 min and maximum frequency f max ;

[0048] Step 5: Based on the minimum frequency f min and maximum frequency f max The sound absorption coefficient was determined to be α. max / 2 corresponds to the frequency band Δf = [f min ,f max ];

[0049] If α max The minimum frequency f corresponding to / 2 min and maximum frequency f max If it is not within the range of [100, 5000], then according to the actual test results, take the cutoff frequencies at both ends of the range of [100, 5000], that is, the two boundary values ​​of [100, 5000], 100Hz or 5000Hz.

[0050] Step 6: Based on the traffic noise frequency band Δf T Determine the traffic noise bandwidth Card(Δf) T );

[0051] In this invention, the traffic noise frequency band Δf is taken. T = [250, 1000] Hz, the Card function represents the width of the noise frequency band, that is, the length of the interval [250, 1000]: 1000-250=750.

[0052] Step 7: Based on Δf and Δf T Calculate the effective sound absorption frequency band Δf∩Δf of the noise reduction material. T Determine the effective sound absorption bandwidth Card(Δf∩Δf) T );

[0053] Δf∩Δf T This represents the intersection operation of these two bandwidths.

[0054] Step 8: Calculate the noise reduction coefficient ε of the noise reduction material in traffic roads.

[0055] like Figure 1 This invention discloses a method for testing the noise reduction coefficient of a sound barrier material. Targeting the main frequency range of traffic noise, the method uses a reverberation chamber to determine the sound absorption coefficient of the noise reduction material at different frequencies. Then, the maximum sound absorption coefficient α is determined. max Plot the sound absorption curve, and determine half of the maximum sound absorption coefficient α based on the sound absorption coefficient curve. max The minimum frequency f corresponding to / 2 min and maximum frequency f max Then, based on the minimum frequency f min and maximum frequency f max Determine the corresponding frequency band Δf, based on the traffic noise frequency band Δf T Determine the traffic noise bandwidth Card(Δf) T According to Δf and Δf T Determine the effective sound absorption frequency band of the material Δf∩Δf T Determine the effective sound absorption bandwidth Card(Δf∩Δf) T This invention analyzes the sound absorption characteristics of materials to obtain a noise reduction coefficient ε. A larger noise reduction coefficient ε indicates a better noise reduction effect of the material. Therefore, this method can determine the noise reduction effect of a sound barrier by measuring the magnitude of the noise reduction coefficient ε. This invention, combined with the main frequency range of traffic noise, proposes a testing method for the noise reduction coefficient of sound barrier materials, which plays a positive role in material preparation, verification of the noise reduction effect of sound barrier projects, and reduction of noise along traffic routes.

[0056] In specific implementation, in step 2, when no plate-shaped test piece is placed in the reverberation chamber, the calculation formula for the sound absorption A1 of the open reverberation chamber is as follows:

[0057]

[0058] In formula (1), V is the volume of the open reverberation chamber, c1 is the speed of sound in the air in the open reverberation chamber, T1 is the reverberation time of the open reverberation chamber, and m1 is the sound intensity attenuation coefficient under the open reverberation chamber condition.

[0059] After placing the plate-shaped test specimen, the formula for calculating the sound absorption A2 of the reverberation chamber is as follows:

[0060]

[0061] In formula (2), c2 is the speed of sound in the air in the reverberation chamber after the plate-shaped test piece is placed; T2 is the reverberation time of the reverberation chamber after the plate-shaped test piece is placed; and m2 is the sound intensity attenuation coefficient under the reverberation chamber conditions after the plate-shaped test piece is placed.

[0062] like Figure 3 and Figure 5 This is a schematic diagram of the reverberation chamber method test. The sound intensity attenuation coefficient of the same reverberation chamber is constant. In Examples 1 and 2, m1 = m2.

[0063] In specific implementation, in step 2, the sound absorption A of the plate-shaped test piece T The calculation formula is:

[0064]

[0065] The sound absorption coefficient α s The calculation formula is:

[0066]

[0067] In formula (4), S is the area of ​​the plate-shaped test piece, i.e. Figure 2 , Figure 3 and Figure 5 The area of ​​the upper surface of the plate-shaped test piece.

[0068] In specific implementation, in step 4, if α max The minimum frequency f corresponding to / 2 min and maximum frequency f max If the frequency is not within the range [100, 5000], then the minimum frequency f is taken. min =100Hz or maximum frequency f max =5000Hz.

[0069] In specific implementation, in step 5, based on the traffic noise frequency band Δf T Traffic noise frequency band Δf T The bandwidth is Card(Δf) T ).

[0070] In specific implementation, the formula for calculating the noise reduction coefficient ε is as follows:

[0071]

[0072] The present invention will be further described below through two specific embodiments, in conjunction with the accompanying drawings.

[0073] Example 1

[0074] like Figure 3 The study focused on granular rock slabs. The area S of the granular rock slab specimen was 11.76 m². 2 The volume V of the reverberation chamber is 237m³. 3 With an air temperature of 15℃, and under both empty and reverberation chamber conditions after placing the test specimen, the speeds of sound in the air, c1 and c2, are 340.45 m / s. According to the test specification "Measurement of Sound Absorption in Reverberation Chambers" (GB / T 20247-2006), the reverberation time T1 in the empty reverberation chamber and the reverberation time T2 in the reverberation chamber after placing the test specimen were measured, as shown in Table 1 below.

[0075] Table 1. Reverberation times T1 and T2 of the empty and placed reverberation chambers for granular rock slab material in Example 1.

[0076] Frequency / Hz 100 125 160 200 250 315 400 500 630 <![CDATA[T1 / s]]> 10.37 10.18 9.53 9.35 8.10 7.66 6.11 4.84 3.80 <![CDATA[T2 / s]]> 10.53 10.64 11.21 11.34 10.49 10.85 8.83 8.17 6.80 Frequency / Hz 800 1000 1250 1600 2000 2500 3150 4000 5000 <![CDATA[T1 / s]]> 3.15 2.85 2.55 2.34 2.09 1.86 1.54 1.27 1.02 <![CDATA[T2 / s]]> 6.08 5.89 5.62 4.92 3.93 3.13 2.36 1.74 1.33

[0077] In Table 1, taking a center frequency of 1000Hz in the 1 / 3 octave band as an example, the sound absorption A of the plate-shaped test piece at a frequency of 1000Hz is calculated according to formula (3). T Where V = 237m 3 c1=c2=340.45m / s, T1=2.85s, T2=5.89s; in this embodiment 1, m1=m2.

[0078]

[0079] Then, according to formula (4), the sound absorption coefficient αs at a frequency of 1000Hz is calculated. S = 11.76m 2 .

[0080]

[0081] Taking this as an example, calculate the sound absorption coefficient α at the 18 1 / 3 octave band center frequencies in Table 1 above. s The calculation results are shown in Table 2.

[0082] Table 2 Sound absorption coefficient α of granular rock slab material at different 1 / 3 octave band center frequencies in Example 1 s

[0083] Frequency / Hz 100 125 160 200 250 315 400 500 630 <![CDATA[Sound absorption coefficient α s > 0.00 0.01 0.05 0.06 0.09 0.13 0.16 0.28 0.38 Frequency / Hz 800 1000 1250 1600 2000 2500 3150 4000 5000 <![CDATA[Sound absorption coefficient α s > 0.50 0.59 0.70 0.73 0.74 0.71 0.74 0.70 0.76

[0084] Based on the data in Table 2, plot the sound absorption coefficient curve of Example 1, as follows: Figure 4 As shown.

[0085] Table 2 shows that the maximum sound absorption coefficient α of the granular rock slab is... max The maximum sound absorption coefficient α is 0.76. maxHalf of α max / 2 equals 0.38. For example... Figure 4 The noise frequency corresponding to 0.38 is 630Hz on the left, which is the minimum frequency f. min =630Hz; if the other end on the right exceeds the cutoff frequency of 5000Hz, then the maximum frequency f is taken. max =5000Hz. Then α max / 2 = 0.38 corresponds to a frequency band of Δf = [630, 5000] Hz. In Example 1, the traffic noise frequency band Δf... T = [250, 1000] Hz, calculate the traffic noise bandwidth Card(Δf) T )as follows.

[0086] Card(Δf T ) = 1000 - 250 = 750

[0087] The effective sound absorption frequency band of the granular rock slab is Δf∩Δf T =[630,1000]∩[250,1000]=[630,1000]Hz, calculate the effective sound absorption bandwidth of the granular rock slab Card(Δf∩Δf) T )as follows.

[0088] Card(Δf∩Δf T ) = 1000 - 630 = 270

[0089] Then, according to formula (5), the noise reduction coefficient ε = 0.27 is calculated. The specific calculation process is as follows.

[0090]

[0091] Example 2

[0092] like Figure 5 The study focused on a double-coated metal plate. The area S of the double-coated metal plate specimen was 11.76 m². 2 The volume V of the reverberation chamber is 237m³. 3 With an air temperature of 18℃, and under both empty and reverberation chamber conditions after placing the test specimen, the sound propagation speeds in the air, c1 and c2, are both 342.45 m / s. According to the test specification "Measurement of Sound Absorption in Reverberation Chambers" (GB / T 20247-2006), the reverberation time T1 in the empty reverberation chamber and the reverberation time T2 in the reverberation chamber after placing the test specimen were measured, as shown in Table 3.

[0093] Table 3. Reverberation times T1 and T2 of double-coated metal plate material in open and placed reverberation chambers in Example 2.

[0094] Frequency / Hz 100 125 160 200 250 315 400 500 630 <![CDATA[T1 / s]]> 3.76 3.94 3.21 2.71 2.48 2.61 2.39 2.39 2.47 <![CDATA[T2 / s]]> 11.29 11.28 11.02 11.12 10.42 10.77 8.73 8.12 7.03 Frequency / Hz 800 1000 1250 1600 2000 2500 3150 4000 5000 <![CDATA[T1 / s]]> 2.35 2.44 2.49 2.47 2.42 2.27 2.09 1.79 1.50 <![CDATA[T2 / s]]> 6.58 6.70 6.95 6.59 5.78 4.90 3.86 2.96 2.19

[0095] Similar to Example 1, in Table 3, taking a 1 / 3 octave band center frequency of 1000Hz as an example, the sound absorption A of the plate-shaped test piece at a frequency of 1000Hz is calculated according to formula (3). T Where V = 237m 3 , c1=c2=342.25m / s, T1=2.44s, T2=6.70s; m1=m2.

[0096]

[0097] Then, according to formula (4), the sound absorption coefficient α at a frequency of 1000Hz is calculated. s S = 11.76m 2 .

[0098]

[0099] Taking this as an example, calculate the sound absorption coefficient α at the 18 1 / 3 octave band center frequencies in Table 3 above. s The calculation results are shown in Table 4.

[0100] Table 4. Sound absorption coefficient α of double-coated metal plate material in Example 2 at different 1 / 3 octave band center frequencies. s

[0101] Frequency / Hz 100 125 160 200 250 315 400 500 630 <![CDATA[Sound absorption coefficient α s > 0.58 0.54 0.72 0.91 1.00 0.94 0.99 0.96 0.86 Frequency / Hz 800 1000 1250 1600 2000 2500 3150 4000 5000 <![CDATA[Sound absorption coefficient α s > 0.89 0.85 0.84 0.82 0.78 0.77 0.72 0.71 0.69

[0102] Based on the data in Table 4, plot the sound absorption coefficient curve of Example 2, as follows: Figure 6 As shown.

[0103] Table 4 shows that the maximum sound absorption coefficient α of the double-coated metal plate max The maximum sound absorption coefficient α is 1.00. max Half of 0.5. For example... Figure 6 The frequencies at both the left and right ends corresponding to 0.5 exceed the cutoff frequencies at both ends. Therefore, the minimum frequency f is taken. min =100Hz; if the other end on the right exceeds the cutoff frequency of 5000Hz, then the maximum frequency f is taken. max =5000Hz.

[0104] Therefore, Δf = [100, 5000] Hz. Traffic noise frequency band Δf in Example 2 T = [250, 1000] Hz, calculate the traffic noise bandwidth Card(Δf) T )as follows.

[0105] Card(Δf T ) = 1000 - 250 = 750

[0106] The effective sound absorption frequency band of the double-coated metal plate is Δf∩Δf T =[100,5000]∩[250,1000]=[250,1000]Hz, calculate the effective sound absorption bandwidth of the double-coated metal plate Card(Δf∩Δf) T )as follows.

[0107] Card(Δf∩Δf T ) = 1000 - 250 = 750

[0108] Then, according to formula (5), the noise reduction coefficient ε = 1 is calculated. The specific calculation process is as follows.

[0109]

[0110] The noise reduction coefficients ε = 0.27 for the granulated rock slab and ε = 1 for the double-coated metal slab demonstrate that the noise reduction effect of the double-coated metal slab is significantly greater than that of the granulated rock slab. This provides staff with a direct and accurate understanding of the noise reduction performance of the two materials.

[0111] The present invention provides a method for testing the noise reduction coefficient of sound barrier materials. Finally, based on the calculated noise reduction coefficient ε, the noise reduction effect of the noise reduction material in traffic is determined, thereby enabling a quantitative description and analysis of the noise reduction effect of the sound barrier.

[0112] The method for testing the noise reduction coefficient of sound barrier materials of the present invention uses the reverberation chamber method to determine the sound absorption coefficient of the material at different frequencies. Based on the maximum sound absorption coefficient and the effective sound absorption frequency band, the sound absorption characteristics of the material are analyzed. Combined with the main frequency range of traffic noise, this method has a positive effect on the preparation of materials, the verification of the noise reduction effect of sound barrier projects, and the reduction of traffic noise.

[0113] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0114] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for testing the noise reduction coefficient of a sound barrier material, characterized in that, Includes the following steps: Step 1: The noise reduction material used to manufacture the sound barrier is made into a plate-shaped test piece; Step 2: Using the reverberation chamber method, measure the noise reduction material at 100 Hz ≤ f Sound absorption coefficient at different frequency bands ≤5000Hz α s And plot the sound absorption coefficient curve; Step 3: Based on the sound absorption coefficient α s And the sound absorption coefficient curve, to determine the maximum sound absorption coefficient of the noise reduction material. α max ; Step 4: Determine half of the maximum sound absorption coefficient based on the sound absorption coefficient curve. α max The minimum frequency corresponding to / 2 and maximum frequency ; Step 5: Based on the minimum frequency and maximum frequency The sound absorption coefficient was determined to be α max / 2 corresponds to the frequency band ; Step 6: Based on traffic noise frequency bands Determine the bandwidth of traffic noise ; Step 7: According to and Calculate the effective sound absorption frequency band of noise reduction materials Determine the effective sound absorption bandwidth ; Step 8: Calculate the noise reduction coefficient of the noise reduction material in traffic roads. ε; The noise reduction coefficient ε The calculation formula is: （5）； In formula (5), α max This represents the maximum sound absorption coefficient of the noise reduction material. For traffic noise bandwidth, The effective sound absorption bandwidth of noise reduction materials.

2. The method for testing the noise reduction coefficient of a sound barrier material according to claim 1, characterized in that, In step 2, when no plate-shaped test piece is placed in the reverberation chamber, the formula for calculating the sound absorption A1 of the empty reverberation chamber is as follows: （1） In formula (1), V is the volume of the open reverberation chamber, c1 is the speed of sound in the air in the open reverberation chamber, and T1 is the reverberation time of the open reverberation chamber. m1 is the sound intensity attenuation coefficient under the condition of an empty reverberation chamber; After placing the plate-shaped test specimen, the formula for calculating the sound absorption A2 of the reverberation chamber is as follows: （2） In formula (2), c2 is the speed of sound in the air in the reverberation chamber after the plate-shaped test piece is placed; T2 is the reverberation time of the reverberation chamber after the plate-shaped test piece is placed; and m2 is the sound intensity attenuation coefficient under the reverberation chamber conditions after the plate-shaped test piece is placed.

3. The method for testing the noise reduction coefficient of a sound barrier material according to claim 2, characterized in that, In step 2, the sound absorption A of the plate-shaped test piece T The calculation formula is: （3） The sound absorption coefficient α s The calculation formula is: （4） In formula (4), S is the area of ​​the plate-shaped test piece.

4. The method for testing the noise reduction coefficient of a sound barrier material according to claim 1, characterized in that, In step 4, if α max The minimum frequency corresponding to / 2 and maximum frequency If the frequency is not within the range of [100, 5000], then the minimum frequency is taken. =100 Hz or maximum frequency =5000 Hz.

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