**2.1 Practical application of the method**

An applied experiment has been carried out to check the correctness, validity, and practicability of this new methodology to quickly detect in situ acoustic leakages.

Specifically, in situ measurements were performed through multiple testing of various partition elements present in different buildings. Partition elements were chosen as a broad sample of the most common elements in use, both by their typology and materials [23]. Eight different partition elements were selected to validate the method, such as laminated plasterboard wall and different kinds of homogeneous or heterogeneous doors made of metal, wood, or glass. The assessment of those doors considered their placement onto either a plasterboard system partition element or a normal brick wall, with better sound insulation properties than the door itself; in all cases, walls with minimum indirect transmission conditions were selected (i.e., surrounding walls with heavy elements and T junctions, without ventilation grids nor cabling boxes) [24]. **Figure 1** displays all the partition elements under study. **Table 1** summarizes the main features of the performed tests, where


To perform beamforming and SONAH measurements, an 18-microphone slice wheel array (**Figure 2**) was used. Ten-second time signals were recorded with the array linked to a data acquisition system with a sample frequency of 65,536 Hz [25] governed by a computer.

In the beamforming measurements performed, the distances varied between 2 and 5 m from the partition element. **Figure 3** shows the beamforming layout used to carry out the measurements.

To process the data, the delay-and-sum algorithm was used over a flat grid with a maximum x/y axis spacing of 0.05 m. With this algorithm and an array diameter of 35 cm, the minimum working frequency would be about 1 kHz, according to Eq. (6). Moreover, defining a threshold *<sup>T</sup>* <sup>=</sup> −8 *dB*, as it is established by the manufacturer of the array for the delay-and-sum algorithm, and taking into account the array characteristics, applying Eq. (7), a fmax(30°) about 6143 Hz is obtained [26]. Taking this into account, the frequency range was defined from the third octave band centered on 1 kHz to the one centered on 5 kHz.

In SONAH measurements, since the array is 35 cm in diameter, they were performed at a distance on 10 cm on areas where fissures could be observed, which can be those characteristic areas of the door made with different materials or because they had some particularities. **Figure 4** shows the SONAH layout used to carry out the measurements.

To process the data, a flat grid with a maximum x/y axis spacing of 0.01 m was used. As the average spacing between measurement points is 0.073 m and D is 0.35 m, and applying Eqs. (8) and (9), the minimum working frequency would

**185**

**Figure 1.**

*In Situ Detection of Leakages in Partition Elements through SONAH and Beamforming Techniques*

be 123 Hz and the maximum working frequency 2353 Hz [26]. Taking this into account, the measurements were taken from the third octave band centered on

 *Photographs of partition elements under study (descriptions of each Id. included in Table 1).*

right. **Figures 3** and **4** show the reference configuration in each case.

Both beamforming and SONAH tests were post-processed considering also the option of including reference signals. In this way, five reference signals were used: two vibrating signals and three sound pressure signals. Since some partition elements are made of two different materials, it was decided to place an accelerometer centered on the surface of each material and three microphones in the array plane along a diagonal line across the assessed surface [27]: top left, center, and bottom

160 Hz to the one centered on 1600 Hz.

*DOI: http://dx.doi.org/10.5772/intechopen.82352*

*In Situ Detection of Leakages in Partition Elements through SONAH and Beamforming Techniques DOI: http://dx.doi.org/10.5772/intechopen.82352*

**Figure 1.**

*Acoustics of Materials*

leakages.

• *Ve* [m3

• *Sse* [m<sup>2</sup>

• *ST* [m2

respectively.

respectively.

tion element.

governed by a computer.

carry out the measurements.

band centered on 1 kHz to the one centered on 5 kHz.

] and *Vr* [m3

] and *Ssr* [m2

**2.1 Practical application of the method**

or intensity levels can be identified. These areas, therefore, corresponding to leaks,

An applied experiment has been carried out to check the correctness, validity, and practicability of this new methodology to quickly detect in situ acoustic

Specifically, in situ measurements were performed through multiple testing of various partition elements present in different buildings. Partition elements were chosen as a broad sample of the most common elements in use, both by their typology and materials [23]. Eight different partition elements were selected to validate the method, such as laminated plasterboard wall and different kinds of homogeneous or heterogeneous doors made of metal, wood, or glass. The assessment of those doors considered their placement onto either a plasterboard system partition element or a normal brick wall, with better sound insulation properties than the door itself; in all cases, walls with minimum indirect transmission conditions were selected (i.e., surrounding walls with heavy elements and T junctions, without ventilation grids nor cabling boxes) [24]. **Figure 1** displays all the partition elements under study. **Table 1** summarizes the main features of the performed tests, where

] are the volume of emitting and receiving rooms,

] is the total surface of partition element or common compartmentaliza-

To perform beamforming and SONAH measurements, an 18-microphone slice wheel array (**Figure 2**) was used. Ten-second time signals were recorded with the array linked to a data acquisition system with a sample frequency of 65,536 Hz [25]

In the beamforming measurements performed, the distances varied between 2 and 5 m from the partition element. **Figure 3** shows the beamforming layout used to

To process the data, the delay-and-sum algorithm was used over a flat grid with a maximum x/y axis spacing of 0.05 m. With this algorithm and an array diameter of 35 cm, the minimum working frequency would be about 1 kHz, according to Eq. (6). Moreover, defining a threshold *<sup>T</sup>* <sup>=</sup> −8 *dB*, as it is established by the manufacturer of the array for the delay-and-sum algorithm, and taking into account the array characteristics, applying Eq. (7), a fmax(30°) about 6143 Hz is obtained [26]. Taking this into account, the frequency range was defined from the third octave

In SONAH measurements, since the array is 35 cm in diameter, they were performed at a distance on 10 cm on areas where fissures could be observed, which can be those characteristic areas of the door made with different materials or because they had some particularities. **Figure 4** shows the SONAH layout used to carry out

To process the data, a flat grid with a maximum x/y axis spacing of 0.01 m was used. As the average spacing between measurement points is 0.073 m and D is 0.35 m, and applying Eqs. (8) and (9), the minimum working frequency would

] are the floor surface of emitting and receiving rooms,

fissures, or sealing defects, are those with higher sound transmission.

**184**

the measurements.

 *Photographs of partition elements under study (descriptions of each Id. included in Table 1).*

be 123 Hz and the maximum working frequency 2353 Hz [26]. Taking this into account, the measurements were taken from the third octave band centered on 160 Hz to the one centered on 1600 Hz.

Both beamforming and SONAH tests were post-processed considering also the option of including reference signals. In this way, five reference signals were used: two vibrating signals and three sound pressure signals. Since some partition elements are made of two different materials, it was decided to place an accelerometer centered on the surface of each material and three microphones in the array plane along a diagonal line across the assessed surface [27]: top left, center, and bottom right. **Figures 3** and **4** show the reference configuration in each case.


### **Table 1.**

*Features of testing environment.*

The post-processed calculations with the reference signals were as follow:


The best results were obtained in beamforming measurements without using references at all and using the central microphone of the array or accelerometers located in areas with different materials in SONAH measurements.

**187**

treated in a similar way.

*Example of the beamforming measurement layout.*

**Figure 3.**

degree of accuracy in all the cases.

*In Situ Detection of Leakages in Partition Elements through SONAH and Beamforming Techniques*

As the amount of data collected is very large, only the results for the base partition element and a typical and representative example for one of the doors (antipanic door, **Figure 1**; Id. 3) are exposed. The remaining elements under study were

In order to compare the results obtained with those from a standardized technique, the partition elements under test were also measured using the intensity standard described in ISO 15186-2 [2]. The configuration of the emitting room was the same than in the array-based measurements. In the receiving room, measurement grids with at least one point every 30 cm in horizontal and 40 cm in vertical were defined, carrying out two measurement sequences and averaging in each measurement point the intensity obtained for both measurements. Twenty-second measurements were taken in each measurement point using the 12-mm separator, which make possible the measure in a frequency range from the third octave band centered on 200 Hz to the one centered on 5 kHz. Moreover, the calculation of field indicators (*F2, F3, F4*) according to ISO 9614-1 [3] was performed to evaluate the accuracy of the measurements. Favorable results were obtained for the engineering

The base partition element consists of a laminated plasterboard wall built on metal profiles. Even though there are other eligible elements such as brick or plaster walls, the laminated plasterboard wall is proposed as a base reference due to the extensive bibliography available for such element [28]. In addition, this element is

*DOI: http://dx.doi.org/10.5772/intechopen.82352*

*In Situ Detection of Leakages in Partition Elements through SONAH and Beamforming Techniques DOI: http://dx.doi.org/10.5772/intechopen.82352*

**Figure 3.** *Example of the beamforming measurement layout.*

As the amount of data collected is very large, only the results for the base partition element and a typical and representative example for one of the doors (antipanic door, **Figure 1**; Id. 3) are exposed. The remaining elements under study were treated in a similar way.

In order to compare the results obtained with those from a standardized technique, the partition elements under test were also measured using the intensity standard described in ISO 15186-2 [2]. The configuration of the emitting room was the same than in the array-based measurements. In the receiving room, measurement grids with at least one point every 30 cm in horizontal and 40 cm in vertical were defined, carrying out two measurement sequences and averaging in each measurement point the intensity obtained for both measurements. Twenty-second measurements were taken in each measurement point using the 12-mm separator, which make possible the measure in a frequency range from the third octave band centered on 200 Hz to the one centered on 5 kHz. Moreover, the calculation of field indicators (*F2, F3, F4*) according to ISO 9614-1 [3] was performed to evaluate the accuracy of the measurements. Favorable results were obtained for the engineering degree of accuracy in all the cases.

The base partition element consists of a laminated plasterboard wall built on metal profiles. Even though there are other eligible elements such as brick or plaster walls, the laminated plasterboard wall is proposed as a base reference due to the extensive bibliography available for such element [28]. In addition, this element is

*Acoustics of Materials*

**186**

**Figure 2.**

**Table 1.**

*Features of testing environment.*

*Left, 18-microphone slice wheel array. Right, microphone positions (dimensions are given in meters).*

• Reference with the central microphone of the array

instance **Figure 1**, Id. 8).

across the assessed surface: top left, center, and bottom right

located in areas with different materials in SONAH measurements.

The post-processed calculations with the reference signals were as follow:

• Without reference signals in the calculations (only in the beamforming case)

**Emitter Receiver Surface R'w [dB]**

*Ssr* **[m2 ]** *ST* **[m2 ]**

**Id. Description** *Ve* **16283-1**

 Plasterboard wall 519 181 219 75 16.7 35 *Glass door* 98 33 244 85 5.3 18 Anti-panic door 246 91 124 39 11.9 24 *Wood door-2* 67 25 144 54 12.7 28 Metal door 114 48 200 213 11.9 23 *Wood door* 200 80 350 546 15.0 26 Metal door with glass spyhole 204 82 280 62 8.0 21 *Wood door with glass window* 421 145 170 60 8.5 19

*Sse* **[m2 ]**

*Vr* **[m3 ]**

**[m3 ]** **ISO** 

• Reference with three ½" microphones in the array plane along a diagonal line

• One accelerometer at the surface center in homogeneous elements or two accelerometers centered on the center of each material/surface for elements made of two different materials (e.g., wooden door with glass window—for

The best results were obtained in beamforming measurements without using references at all and using the central microphone of the array or accelerometers

**Figure 4.** *Example of the SONAH measurement layout.*

frequently used either independently or combined with doors as partition solutions, forming vertical walls between rooms.

**Figure 5** shows the results through intensity and beamforming for the whole wall and through SONAH in three points of the wall in the third octave band. It can be observed, in the three images, that the wall is homogeneous separating element without leaks and, as a consequence, the intensity and pressure maps are uniform over all the surface of the element without leakages or fissures.

In the case of the anti-panic door, **Figure 6** shows the results obtained. **Figure 6(a)** shows the graphical results obtained from the sound intensity measurements (the upper-left point should not be considered because a measurement error took place). Analyzing the results obtained, it is possible to observe that the door exhibits a very homogeneous behavior with very little differences in sound intensity transmission and in addition in the sound insulation. Taken into account that, according to the intensity standard ISO-15186-2 [2], it is not possible to expand the measurement grid until the floor, it was not possible to identify the leakage in the bottom part of the door because the measurement grid does not cover this part.

The sound pressure maps obtained with beamforming and SONAH are those shown in **Figure 6(b)** and **(c)**, where it is possible to observe the areas where there is a higher sound pressure level emitted, in other words, the areas with the lower sound insulation. This area is located at the bottom of the door, because there is no adjustment between the door and the floor. The rest of the door exhibits a very homogeneous behavior because there is a big difference in sound pressure level among the main noise source and the rest ones.

**189**

*range.*

**Figure 5.**

*In Situ Detection of Leakages in Partition Elements through SONAH and Beamforming Techniques*

*Results obtained for the base element. (a) Intensity map (200–5 kHz). (b) Pressure map with Beamforming (1-5 kHz) with 10 dB dynamic range. (c) Pressure map with SONAH (160-1600 Hz) with 10 dB dynamic* 

*DOI: http://dx.doi.org/10.5772/intechopen.82352*

*In Situ Detection of Leakages in Partition Elements through SONAH and Beamforming Techniques DOI: http://dx.doi.org/10.5772/intechopen.82352*

*Acoustics of Materials*

frequently used either independently or combined with doors as partition solutions,

**Figure 5** shows the results through intensity and beamforming for the whole wall and through SONAH in three points of the wall in the third octave band. It can be observed, in the three images, that the wall is homogeneous separating element without leaks and, as a consequence, the intensity and pressure maps are uniform

In the case of the anti-panic door, **Figure 6** shows the results obtained. **Figure 6(a)** shows the graphical results obtained from the sound intensity measurements (the upper-left point should not be considered because a measurement error took place). Analyzing the results obtained, it is possible to observe that the door exhibits a very homogeneous behavior with very little differences in sound intensity transmission and in addition in the sound insulation. Taken into account that, according to the intensity standard ISO-15186-2 [2], it is not possible to expand the measurement grid until the floor, it was not possible to identify the leakage in the bottom part of the door because

The sound pressure maps obtained with beamforming and SONAH are those shown in **Figure 6(b)** and **(c)**, where it is possible to observe the areas where there is a higher sound pressure level emitted, in other words, the areas with the lower sound insulation. This area is located at the bottom of the door, because there is no adjustment between the door and the floor. The rest of the door exhibits a very homogeneous behavior because there is a big difference in sound pressure level

over all the surface of the element without leakages or fissures.

forming vertical walls between rooms.

*Example of the SONAH measurement layout.*

the measurement grid does not cover this part.

among the main noise source and the rest ones.

**188**

**Figure 4.**

### **Figure 5.**

*Results obtained for the base element. (a) Intensity map (200–5 kHz). (b) Pressure map with Beamforming (1-5 kHz) with 10 dB dynamic range. (c) Pressure map with SONAH (160-1600 Hz) with 10 dB dynamic range.*

**Figure 6.**

*Results obtained for the anti-panic door. (a) Sound intensity map (200–5 kHz), (b) pressure map with beamforming (1–5 kHz) with 10 dB dynamic range, and (c) pressure map with SONAH in the door center (160–1600 Hz) with 10 dB dynamic range.*

If both measurements are compared, the results show a similar behavior, but intensity measurements do not identify the leakage at the bottom part of the door due to the measurement grid chosen.
