BSI Standards PublicationRailway applications — Track — Noise barriers and related devices acting on airborne sound propagation — Test method for determining the acoustic performance Par
General principle
The sound source generates a transient sound wave that interacts with the device under test, resulting in reflection, transmission, and diffraction A microphone positioned on the opposite side captures both the transmitted sound wave and the diffracted wave from the device's top edge, ensuring that diffraction from the lateral edges is sufficiently delayed for accurate measurement By repeating the measurement without the device, the direct free-field wave can be obtained Analyzing the power spectra of both the direct and transmitted waves allows for the calculation of the sound insulation index.
The sound insulation index shall be the logarithmic average of the values measured at nine points placed on the measurement grid (scanning points) See Figure 3 and Formula (1)
Measurements should be conducted in a reflection-free sound field within the Adrienne temporal window To achieve this, it is advisable to acquire an impulse response with sharp peaks, allowing for the identification and rejection of reflections from other surfaces based on their delay time.
Measured quantity
The expression used to compute the sound insulation index SI as a function of frequency, in one-third octave bands, is:
∆ n ∆ k f ik ik f tk tk j j j df t w t h F df t w t h F
The incident reference component of the free-field impulse response at the k-th scanning point is denoted as \$h_{ik}(t)\$, while the transmitted component is represented by \$h_{tk}(t)\$ Additionally, the time window for the incident reference component is indicated as \$w_{ik}(t)\$, and the time window for the transmitted component is denoted as \$w_{tk}(t)\$.
F is the symbol of the Fourier transform;
Test arrangement
The test method can be utilized both in situ and on a specially constructed barrier sample designed for testing In the latter scenario, the specimen should be constructed according to the specifications outlined in Figure 7.
— a first part, composed of acoustic elements;
— a post (if applicable for the specific noise reducing device under test);
— a second part, composed of acoustic elements
The test specimen shall be mounted and assembled in the same manner as the manufactured device is used in practice with the same connections and seals
The measurement area is defined as a circle with a radius of 2 meters, centered in the middle of the grid Each sample must be sufficiently large to fully encompass this circle for accurate measurements.
The minimum distance between two posts for laboratory measurements is set at L = 4 m, which also defines the length of the minimum sample required for accurate measurements in controlled conditions.
For qualifying the sound insulation index of posts only, it is only necessary to have acoustic elements that extend
2 m or more on either side of the post, so that L tot = 4 m (see Figure 7 b))
For devices with a post separation of less than 4 m, the distance between posts must be adjusted accordingly, ensuring that the total minimum construction length remains at 6 m This is illustrated in Figure 7 The article also discusses sound insulation index measurements for various configurations: a) measurements for elements and posts, b) measurements in front of a single post, and c) measurements for samples with post separations smaller than 4 m.
Key dotted circles: tested area for posts L distance between two posts thin circles: tested area for elements L tot overall minimum length [m] h B barrier height [m]
Figure 7 — Sketch of the minimum sample required for measurements in laboratory conditions
1 measurement grid h B noise barrier height [m]
2 loudspeaker front panel h S reference height [m] d M distance nois barrier to measurment = 0,25 m t B noise barrier thickness [m] d S distance noise barrier to speaker = 1 m
The setup for measuring the sound insulation index involves normal incidence of sound on the sample, with transmitted component measurements taken in front of various types of noise barriers These include flat, concave, convex, and inclined barriers, each providing distinct data on sound transmission.
1 measurement grid h B noise barrier height [m]
2 loudspeaker front panel h S reference height [m] d S distance noise barrier to speaker = 1 m t B noise barrier thickness [m] d M distance noise barrier to measurement = 0,25 m
Figure 9 — (not to scale - informative) Examples of the set-up for the sound insulation index measurement
— Normal incidence of sound on the sample
Figure 10 — Sketch representing the essential components of the measuring system
Measuring equipment
Components of the measuring system
The measuring equipment includes an electro-acoustic system featuring an electrical signal generator, a power amplifier, and a loudspeaker It also consists of one or nine microphones with their respective microphone amplifiers, along with a signal analyzer that can perform transformations between the time and frequency domains.
NOTE Some of these components can be integrated into a frequency analyser or a personal computer equipped with specific add-on board(s)
The essential components of the measuring system are shown in Figure 10
The complete measuring system shall meet the requirements of at least a type 1 instrument in accordance with
EN 61672-1, except for the microphone which shall meet the requirements for type 2 and have a diameter of 1/2” maximum
The measurement procedure outlined relies on the ratios of power spectra from impulse responses captured using identical equipment and conditions over a brief period High precision in sound level measurement is not a priority, eliminating the need for stringent absolute accuracy in the measurement chain Additionally, the microphones must be compact and lightweight to be securely mounted on a frame, forming a stable microphone grid, while adhering to type 2 requirements.
Sound source
The electro-acoustic sound source shall meet the following characteristics:
— have a single cone full range driver (from 100 Hz to 5 kHz in one-third octave bands);
— be constructed without any port, e.g to enhance low frequency response;
— have a smooth magnitude of the frequency response without sharp irregularities throughout the measurement frequency range, resulting in an impulse response under free-field conditions with a length not greater than
Test signal
The electro-acoustic source requires a deterministic and repeatable input electrical signal, which must be carefully configured to prevent any nonlinearity in the loudspeaker's performance.
The S/N ratio is improved by repeating the same test signal and synchronously averaging the microphone response At least 16 averages shall be kept
This European Standard advocates for the use of a MLS signal as the preferred test signal, although alternative signals such as sine sweeps may be utilized if it can be conclusively demonstrated that the results are identical.
— the generation of the test signal is deterministic and exactly repeatable;
— impulse responses are accurately sampled (without distortion) on the whole frequency range of interest (one- third octave bands between 100 Hz and 5 kHz);
The test method demonstrates strong immunity to background noise, achieving an effective signal-to-noise (S/N) ratio exceeding 10 dB across the entire frequency range of interest This performance is accomplished within a brief measurement time, with each impulse response taking no longer than 5 minutes.
Choosing a sufficiently high sample rate enables precise correction of potential time shifts in impulse responses between the measurements taken in front of the sample and those in free-field conditions, which may be affected by temperature variations.
— the test signal is easy-to-use, i.e it can be conveniently generated and fed to the sound source using only equipment which is available on the market.
Data processing
Sample rate
The frequency at which the microphone response is sampled depends on the specified upper frequency limit of the measurement and on the anti-aliasing filter type and characteristics
The sample rate f s shall have a value greater than 43 kHz
Meeting the Nyquist criterion ensures a clear definition of the signal, but higher sample rates enhance signal reproduction and provide precise waveform details With appropriate sample rates, it becomes easier to detect and correct errors, such as time shifts in impulse responses caused by temperature variations between the sample measurement and free-field measurement.
The sample rate shall be equal to the clock rate of the signal generator
The cut-off frequency of the anti-aliasing filter, f co , shall have a value: s f co k f f ≤ (2) where k f is 1/3 for the Chebyshev filter and k f = 1/4 for the Butterworth and Bessel filters
For each measurement, the sample rate, the type and the characteristics of the anti-aliasing filter shall be clearly stated in each test report.
Background noise
The effective signal-to-noise ratio S/N, taking into account sample averaging, shall be greater than 10 dB over the frequency range of measurements
NOTE Coherent detection techniques, such as the MLS cross-correlation, provide high S/N ratios.
Scanning technique using a single microphone
The sound source shall be positioned as described in 3.11
The measurement grid must be square, with a side length of 0.80 m, centered at the reference height \( h_S \) It should be positioned facing the side of the noise barrier that is not exposed to noise, ensuring a horizontal distance of \( d_M = 0.25 \) m from the microphone reference plane Additionally, the grid should be placed as far as possible from the edges of the noise barrier being tested.
A single microphone will be positioned at nine scanning points to measure the resulting impulse responses Each response includes the direct component, the transmitted component through the device under test, diffracted components, and additional parasitic reflections.
A “free-field” impulse response shall be measured for each microphone position, keeping the supporting frame with the same geometrical configuration of the set-up and without the barrier present
In particular, the distance d T of the microphone position n Five from the sound source shall be kept constant (see Figure 6): where t B is the barrier thickness (see 3.10)
Care shall be taken that the supporting frame does not alter the measurement result.
Scanning technique using nine microphones
Alternatively to the procedure described in 5.5.4, the procedure described here may be used, leading to the same results
The sound source shall be positioned as described in 3.11
The measurement grid must be square with a side length of 0.80 m, centered at the reference height \( h_S \) It should be positioned facing the side of the noise barrier that is not exposed to noise, ensuring a horizontal distance of \( d_M = 0.25 \) m from the microphone reference plane Additionally, the grid should be placed as far as possible from the edges of the noise barrier being tested.
A rigid frame will support a set of nine microphones positioned at designated scanning points on the measurement grid, allowing for the simultaneous or sequential measurement of nine impulse responses Each impulse response includes the direct component, the transmitted component through the device under test, diffracted components, and additional parasitic reflections.
A “free-field” impulse response shall be measured for each microphone position, keeping the supporting frame with the same geometrical configuration of the set-up and without the barrier present
In particular, the distance d T of the microphone position n Five from the sound source shall be kept constant (see Figure 6): t B d t d d T = s + B + M =1,25+ (3) where t B is the barrier thickness (see 3.10)
Care shall be taken that the supporting frame does not alter the measurement result.
Adrienne temporal window
For the purpose of this European Standard, windowing operations in the time domain shall be performed using a temporal window, called Adrienne temporal window, with the following specifications (see Figure 11):
— a leading edge having a left-half Blackman-Harris shape and a total length of 0,5 ms (“pre-window”);
— a flat portion having a total length of 5,18 ms (“main body”);
— a trailing edge having a right-half Blackman-Harris shape and a total length of 2,22 ms
The total length of the Adrienne temporal window is T W , ADR =7,9 ms
NOTE A four-term full Blackman-Harris window of length T W,BH is: where: a0 = 0,358 75; a1 = 0,488 29; a2 = 0,141 28; a3 = 0,011 68;
Y adrienne window function w(t) [relative units]
Figure 11 — The Adrienne temporal window, with the marker point MP
In exceptional cases where the window length \( T_W \) and Average Daily Rate (ADR) need to be adjusted, the lengths of the flat portion and the right-half Blackman-Harris portion should maintain a ratio of 7:3 For instance, when conducting tests on very large samples, increasing the window length can enhance the low-frequency limit.
The point where the flat portion of the Adrienne temporal window begins is called the marker point (MP).
Placement of the Adrienne temporal window
For the “free-field” direct component, the Adrienne temporal window shall be placed as follows:
— the first peak of the impulse response, corresponding to the direct component, is detected;
— a time instant preceding the direct component peak of 0,2 ms is located;
— the direct component Adrienne temporal window is placed so that its marker point corresponds to this time instant
In other words, the direct component Adrienne temporal window is placed so that its flat portion begins 0,2 ms before the direct component peak
For the transmitted component, the Adrienne temporal window shall be placed as follows:
— the time instant when the transmission begins is located, possibly with the help of geometrical computation (conventional beginning of transmission);
— a time instant preceding the conventional beginning of transmission of 0,2 ms is located;
— the transmitted component Adrienne temporal window is placed so that its marker point corresponds to this time instant;
— the time instant when the diffraction begins is located, possibly with the help of geometrical computation (conventional beginning of the diffraction);
— the transmitted component Adrienne temporal window stops 7,4 ms after the marker point or at the conventional beginning of the diffraction, whichever of the two comes first
The Adrienne temporal window for the transmitted component is positioned such that its flat section starts 0.2 ms prior to the initial peak and its tail concludes before the onset of diffraction (refer to Figure 12).
In computations involving the speed of sound c, its temperature dependent value shall be assumed
2 diffracted component Y impulse response [relative units]
Figure 12 — Example of application of the Adrienne temporal window to the transmitted component of an impulse response
Low frequency limit and sample size
— the sound components diffracted by the edges of the noise barrier under test;
— the sound components reflected by the ground on the receiver or source side of the noise barrier under test
For noise barriers having a height smaller than the length, the most critical component is that diffracted by the top edge and therefore the critical dimension is the height
For noise barriers shorter than their length, the low frequency limit (\$f_{min}\$) for sound insulation index measurements is illustrated in Figure 13 This graph applies to acoustic barriers with negligible thickness; however, for thicker noise barriers, the low frequency limit decreases.
For qualification tests, samples must meet the minimum dimensions outlined in section 5.3 (refer to Figure 7) This requirement establishes a low frequency limit for the sound insulation index at approximately 166 Hz, meaning that measurements are valid down to the 200 Hz one-third octave band Values measured below 166 Hz may be retained for informational purposes.
Y low frequency limit f min [Hz]
Figure 13 — Low frequency limit of sound insulation index measurements as a function of the height of the
Positioning of the measuring equipment
Selection of the measurement positions
The measuring equipment shall be placed near the noise barrier to be tested in positions selected according to the following rules
Distances must be measured with a relative uncertainty of no more than 1% of their nominal values The measurement grid is positioned on the side opposite the noise barrier being tested When using a single microphone, it is placed at each of the nine measurement points on the grid to sample the impulse response at each location.
When the microphone is positioned centrally within the measurement grid, the acoustic center of the sound source must align horizontally with the acoustic center of the microphone.
A "free-field" impulse response will be recorded for each microphone position, ensuring that the supporting frame maintains the same geometric configuration throughout the setup and that the barrier is absent.
The nine measurements collected from the measurement grid, along with the corresponding free-field measurements, will be processed and averaged using the sound insulation index Formula (1) When utilizing a set of nine microphones mounted on a rigid frame, they are positioned at the nine scanning points on the opposite side of the device under test, allowing for simultaneous or sequential measurement of the nine impulse responses.
A “free-field” impulse response shall be measured for each microphone, keeping the supporting frame with the same geometrical configuration of the set-up and without the barrier present (Figure 6).
Post measurements
For noise barriers with intermediate posts, such as acoustic barriers made up of one or more acoustic elements supported by vertical posts at regular intervals, it is essential to conduct nine measurements on the measurement grid Additionally, free-field measurements should be taken both at the center of a representative acoustic element and in front of a representative post.
Additional measurements
If sound leaks are suspected at a different location, such as the bottom edge of the tested barrier, additional measurements should be taken on the measurement grid along with free-field measurements near that area In this scenario, the sound signal from the bottom edge is not a "parasitic" signal but the "transmitted" signal of interest The Adrienne temporal window must be expanded to capture this signal while excluding other parasitic signals, based on geometrical calculations detailed in the test report Notably, ground reflections on the receiver side are not a concern, as the apparent sound source, or leak, is situated on the ground.
Reflecting objects
Reflecting objects, such as safety rails, fences, rocks, and parked cars, can cause parasitic reflections during testing To minimize their impact, these objects should be positioned as far away from the microphone(s) as possible, and a complete description of them must be included in the test report.
Care shall be taken that the microphone stand does not influence the measurement.
Safety considerations
This test method may pose safety risks when conducting measurements near active railways The document does not cover all potential safety issues, and it is the user's responsibility to implement suitable safety and health practices based on a thorough risk assessment.
Sample surface and meteorological conditions
Condition of the sample surface
Measurements should only be conducted on dry sample surfaces unless the goal is to assess the impact of weather or environmental conditions on sound propagation If the sample is anticipated to have a considerable void content, measurements must be postponed until it is confirmed that the pores are dry.
The sample surface temperature shall be within 0 to 70 °C during the measurement.
Wind
Wind speed at microphone positions shall not exceed 5 m/s during the measurements.
Air temperature
The ambient air temperature must range from 0 to 40 °C during measurements When calculating sound speed, it is essential to use the temperature-dependent value based on the actual temperature in the test area.
The evaluation of measurement result uncertainty should align with ISO/IEC Guide 98-3 When reported, the expanded uncertainty must include the corresponding coverage factor for a 95% coverage probability, as specified in the guide Additional details on measurement uncertainty can be found in Annex A.
The measurement process involves several critical steps: First, ensure the sample surface and meteorological conditions meet the specifications outlined in section 5.7; if not, measurements cannot proceed Next, position the measuring equipment according to section 5.6, adhering to safety considerations in 5.6.5 Select and generate the test signal, then sample the total signal received by the microphone(s) at a rate specified in 5.5.2 Process this signal to obtain the overall impulse response at the designated measurement positions If background noise contamination is suspected, average the impulse response data until the desired accuracy is achieved, maintaining at least 16 averages as per section 5.4.3 For each set of nine measurements on the grid, acquire corresponding free-field impulse responses Isolate the direct sound component and those transmitted through the device under test using Adrienne temporal windows, and compute the power spectra of the windowed signals Calculate the sound insulation index according to Formula (1), and if applicable, determine the single-number ratings for elements and posts in accordance with EN 16272-3-2 Finally, evaluate the measurement uncertainty as detailed in Annex A and compile the test report.
Expression of results
The test results will be presented through a graph and a table, displaying the sound insulation index values across one-third octave frequency bands from 100 Hz to 5 kHz If valid measurements cannot be obtained for the entire specified frequency range, the results will be limited to a narrower frequency range, with clear documentation of the reasons for any restrictions.
The values of the sound insulation index shall be rounded off to one decimal place
The measurement uncertainty of the sound reduction index SI shall be given at all frequencies of measurement
If the single-number rating(s) for elements, for posts (if applicable) and globally are to be calculated, this shall be done in accordance to EN 16272-3-2.
Further information
The test report must include a reference to the document, the name and address of the testing organization, and the date and location of the test It should provide a description of the test site, including drawings or pictures of the device under test and the measurement setup, as well as any reflecting or diffracting objects near the maximum sampled area Additionally, the report must detail the noise barrier being tested, including its brand, type, dimensions, age, actual conditions, and composition, such as the number of layers, thicknesses, and material specifications Surface conditions of the noise barrier regarding dryness and temperature, as well as the prevailing meteorological conditions during the test (wind speed, direction, and air temperature), should also be documented The test arrangement must be illustrated with a scale drawing or sketch that includes marked dimensions, along with the length of the Adrienne temporal windows used for analysis and the low frequency limit of the measurement in relation to the smallest dimension of the noise barrier Finally, the report should present the results of the measurements.
1) result of measurements in front of an acoustic element;
2) result of measurements in front of a post (if any);
3) result of measurements at selected locations (if any); n) measurement uncertainty; o) single-number rating(s) of the above result(s), if calculated; p) signature of the person responsible for the measurements
General
The ISO/IEC Guide 98-3 outlines the standard format for expressing uncertainties related to measurement methods This format includes an uncertainty budget that identifies and quantifies all sources of uncertainty, allowing for the calculation of the combined total uncertainty.
This Annex aims to establish a foundation for developing appropriate information for the application of ISO/IEC Guide 98-3 It is important to note that the information provided has not undergone round robin testing, and further research may uncover additional factors Ultimately, it is the responsibility of the laboratory conducting the measurement to assess its uncertainty, which may differ from the data presented; therefore, this annex should be viewed solely as a guide.
Expression for the calculation of sound insulation index
Currently, there is no available information to create an analytical model for the sound insulation index based on multiple input variables Initial estimates suggest that the sound insulation index of a noise-reducing device, denoted as SI\(_j\), as defined by this European Standard, depends on several parameters, represented by the following formula.
The sound insulation index, denoted as S, represents the time and space averaged value in the j-th one-third-octave frequency band Several input quantities account for uncertainties in the measurement process: δ 1 addresses uncertainties in the incident reference component of the free-field impulse response acquisition, while δ 2 accounts for uncertainties in the transmitted components Additionally, δ 3 considers uncertainties related to the measuring equipment, δ 4 pertains to uncertainties from the limited number of microphone and source positions, and δ 5 and δ 6 address fluctuations in air temperature and humidity, respectively.
Each input quantity is linked to a specific probability distribution, such as normal, rectangular, or Student’s t The expectation, or mean value, serves as the most accurate estimate of the input quantity, while the standard deviation indicates the dispersion of values The uncertainty associated with this estimate is known as standard uncertainty, which depends on the standard deviation, the probability distribution, and the number of degrees of freedom.
Contributions to measurement uncertainty
The overall uncertainty in the sound insulation index is influenced by the individual input quantities, their probability distributions, and sensitivity coefficients, denoted as \(c_i\) These sensitivity coefficients indicate the extent to which variations in the input quantities impact the sound insulation index values Mathematically, they are represented as the partial derivatives of the function \(SI_j\).
The overall uncertainty is determined by the contributions of relevant input quantities, which are calculated using the products of their standard uncertainties and corresponding sensitivity coefficients.
Table A.1 — Template for the uncertainty budget
The quantity estimate of the sound insulation index in the j-th one-third octave frequency band, denoted as \( S I_j \), is influenced by standard uncertainty and probability distribution Additionally, the sensitivity coefficient plays a crucial role in determining the normal incident reference component of the free-field impulse response at the k-th scanning point.
, , ( ) i k j h t δ 1 transmitted component of the impulse response at the k-th scanning point
The uncertainties in measurement can be attributed to several factors: δ2 represents the uncertainty from the measuring equipment, δ3 accounts for the uncertainty arising from the limited number of microphone and source positions, δ4 reflects the uncertainty due to variations in air temperature, and δ5 indicates the uncertainty caused by fluctuations in air humidity.
Expanded uncertainty (k is a coverage factor) U = k u -
For the case of negligible correlation between the input quantities, the combined standard uncertainty of the determination of the sound insulation index, u(SI j ), is given by the following Formula:
Research is still needed to establish the standard uncertainties from various contributions Table A.1 provides an example of the information required to calculate the overall uncertainty of the method.
Expanded uncertainty of measurement
The ISO/IEC Guide 98-3 mandates the specification of an expanded uncertainty, denoted as U, ensuring that the interval \([SI_j - U, SI_j + U]\) encompasses approximately 95% of the values attributed to \(SI_j\) To achieve this, a coverage factor \(k\) is utilized, where \(U = k u\) The value of the coverage factor is contingent upon the probability distribution related to the measurand.
Measurement uncertainty based upon reproducibility data
In cases where data for uncertainty contributions is lacking, the standard deviation of reproducibility can serve as an estimate for the combined standard uncertainty in sound insulation index determinations By selecting an appropriate coverage factor, the product of this factor and the standard deviation will provide an estimate of the expanded measurement uncertainty, aligned with the chosen coverage probability Conventionally, a specific coverage probability is utilized in this context.
95 % is usually chosen To avoid any misinterpretations, the chosen coverage probability should always be stated in test reports together with the expanded measurement uncertainty
Measurement reproducibility provides valuable insights for deriving measurement uncertainties; however, it remains insufficient as it lacks a detailed analysis of the different components of measurement uncertainty and their respective magnitudes.
Template of test report on airborne sound insulation of railway noise barriers
Template of test report
for product xxxx produced by the firm yyyyy
The present test is based on the test method according to CEN/TS 16272-5 If the single- number rating is to be calculated, this is done in accordance to EN 16272-3-2
(b) Name and address of testing organization:
(d) Test situation: see description and photographic presentation in B.1
Dimensions: height, length, distance between support posts or ribs
Exposure classes according to EN 60721-3-4:
Physical condition during test (by visual inspection):
Composition: see description and photographic presentation in B.2 Drawings and photographs clearly show how the product is built; include at least front view, side view, back view
(f) Surface conditions of the test object
(g) Meteorological conditions prevailing during the test
The test arrangement must be detailed in accordance with section B.2, including a photographic presentation that clearly illustrates the precise locations of the microphone in relation to the sample It is essential to depict the microphone positions accurately, such as positioning them opposite a ridge on a non-flat product.
Type and characteristics of the anti-aliasing filter:
Smallest dimension of the test object:
(m) Test results: see tables and figures in B.3
The single-number rating for the sound reflection index amounts to:
(p) Signature of the person responsible for the measurements
Test setup (example)
The tested barrier is a single-leaf, reflective timber structure made up of two sections, each consisting of panels measuring 3.0 m wide by 2.0 m high, supported by steel I-section posts spaced 3.0 m apart This design reflects typical construction used alongside highways The overall dimensions of the test configuration are 4.0 m in height and 9.0 m in width, as illustrated in Figure B.1, which depicts the barrier from the front (traffic side).
Figure B.1 — (Example) General view of test barrier (from front (rail) side) – Crosses mark measurement positions based on the post spacing of 3 m
The sound source is positioned 2.0 meters above the ground, with the measurement grid strategically placed midway between the posts and directly in front of a post, as indicated by the crosses in Figure B.1, which represent the approximate locations of the loudspeaker and center microphone axis.
The barrier thickness at the height of measurement is 0,100 m midway between the posts and the post thickness at the height of measurement is 0,205 m
There are no sound reflecting nor sound diffracting parasitic objects acting in the sample area
The test situation including the loudspeaker and microphone array is shown in Figure B.2 a) b) Figure B.2 — (Example) Test arrangement showing loudspeaker and microphone array when measuring across the panel
Test object and test situation (example)
The single-leaf reflective timber noise barrier, as illustrated in Figure B.3, consists of panels made from vertical timber fence boards secured by horizontal rear rails To enhance aesthetics and functionality, vertical cover strips conceal the expansion gaps between the planks on the front Each panel measures 3.0 meters in width and 2.0 meters in height.
The barrier is constructed in two sections On the front of the barrier, the joint between the upper and lower section is sealed by a wide horizontal cover strip
The structure features steel 'I-section' columns measuring 0.105 m in width and 0.205 m in depth, with panels secured between the columns using large timber wedges at the rear.
The measurement points were arranged on the rear of the barrier in a 3 × 3 grid, with equal horizontal and vertical distances of 0.40 m This grid was positioned midway between the posts and aligned with the center of a post, approximately at the height of the joint between the upper and lower sections.
3 main planks 8 vertical cover strip
4 horizontal rail 9 horizontal cover strip
Figure B.3 — (Example) Basic composition of the single elements of the noise barrier
Figure B.4 shows a typical cross-section through the barrier, including the dimensions of the different elements
Dimensions in millimetres a) Plan view of noise barrier b) Cross-section through A-A Key
2 horizontal rail 6 horizontal cover strip at joint between upper and lower panels
Figure B.4 — (Example) Cross-section through noise barrier
Results (example)
B.4.1 Part 1 – Results for ‘element’ in tabular form
Table B.1 — Results for ‘element’ in tabular form
Third-octave band centre frequency
Particular values of sound insulation index SI for “element” for the 9 microphone positions and the logarithmic average
Single number rating of airborne sound insulation for the acoustic element, DL SI,E = 26 dB
B.4.2 Part 2 – Results for ‘element’ in graphic form
X third-octave band centre frequency [Hz]
Figure B.5 — Results in graphic form
B.4.3 Part 3 – Results for ‘post’ in tabular form
Table B.2 — Results for ‘post’ in tabular form
Third-octave band centre frequency
Particular values of sound insulation index SI for “post” for the 9 microphone positions and the logarithmic average
Single number rating of airborne sound insulation for the post, DL SI,P = 21 dB
B.4.4 Part 4 – Results for ‘post’ in graphic form
X third-octave band centre frequency [Hz]
Figure B.6 — Results in graphic form
B.4.5 Part 5 – Results for global condition (average of ‘element’ and ‘post’) in tabular form
Table B.3 — Results for global condition in tabular form
Third-octave band centre frequency
Particular values of sound insulation index SI for “global” condition (average of element and post) for the 9 microphone positions and the logarithmic average
Global single number rating of airborne sound insulation for the test sample, DL SI,G = 23 dB
B.4.6 Part 6 – Results for global condition (average of ‘element’ and ‘post’) in graphic form
X third-octave band centre frequency [Hz]
Figure B.7 — Results in graphic form
The EN 16272-3-1:2012 standard focuses on railway applications, specifically addressing noise barriers and devices that influence airborne sound propagation It outlines a test method for assessing the acoustic performance of these barriers, providing a normalized railway noise spectrum and single number ratings suitable for diffuse field applications.
CEN/TS 16272–5 outlines a test method for assessing the acoustic performance of noise barriers and related devices in railway applications This standard focuses on determining the intrinsic characteristics of these barriers, specifically measuring the in situ values of sound reflection under direct sound field conditions.
EN 60721-3-4, Classification of environmental conditions — Part 3: Classification of groups of environmental parameters and their severities — Section 4: Stationary use at non-weather protected locations (IEC 60721-3-4)
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