AIA-DAGA 2013 Merano
Comparison Between Field Measurements Methods of Acoustic Performances of Buildings Chiara Martina Pontarollo, Antonino Di Bella Department of Industrial Engineering, University of Padova, 35131 Padova, Italy, Email:
[email protected] [email protected]
Introduction The ISO 10052 Standard describe a survey method for building acoustic measurements: airborne and facade sound insulation, impact noise and equipment sound pressure level. Usually, for building acoustic measurements, engineering methods are used. However ISO 10052 survey methods have several advantages in term of measurement and elaboration speed. For a larger diffusion of this standard a comparison between engineering and survey measurements is necessary, especially in term of measurements accuracy (repeatability and reproducibility). ISO 10052 application fields Airborne sound insulation Impact sound insulation Facade sound insulation Service equipment sound
Corresponding engineering standards ISO 140-4 ISO 140-7 ISO 140-5 ISO 16032
Figure 1: Airborne measurements - comparison between single number results using ISO 140-4 and ISO 10052
Table 1: ISO 10052 application fields and corresponding engineering standards
For this scope, in this paper the results of different comparison campaigns between ISO 10052 measurements and respective precision measurements are presented: 1) in situ comparison for airborne, impact and facade sound insulation using Standard ISO 140 parts 4, 5 and 7 and ISO 10052; 2) in situ comparison for equipment noise measurements using Standard ISO 16032 and ISO 10052; 3) interlaboratory test for airborne and impact sound insulation using both Standard ISO 140 parts 4 and 5 and ISO 10052.
Figure 2: Impact measurements - comparison between single number results using ISO 140-7 and ISO 10052
In situ comparison for airborne, impact and facade sound insulation In a residential building with six building units all acoustic verifications have been repeated using both engineering and survey measurement methods. Standard ISO 140 parts 4, 5 and 7 have been used with fixed microphone positions whereas ISO 10052 provide the operator to hold by hand the sound level meter covering a 8 shape path over a time of at least 30 seconds. The operator should stay in the centre of the room and only one position is needed. So the number of sound level acquisitions is very small. Differently from ISO 10052 standard prescriptions sound pressure levels have been measured not only in octave bands but also in 1/3 octave bands.
Figure 3: Facade measurements - comparison between single number results using ISO 140-5 and ISO 10052
Three different cases have been considered:
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AIA-DAGA 2013 Merano 1) levels and reverberation times measured in 1/3 octave bands; 2) levels and reverberation times measured in octave bands; 3) levels measured in octave bands and reverberation time correction given by table (depending on room volume and type: with or without furniture, with soft or hard surfaces). The comparison has been made on: - 28 airborne sound insulation measurements (floors sound reduction measured bidirectionally); - 14 impact level measurements; - 18 facade sound insulation measurements. Comparisons, for single numbers results, are shown on Figures 1, 2 and 3. Using the survey method with 1/3 octave bands single number results are very close to ones obtained using engineering methods. Differences increase using octave band or worse using reverberation time index by table. In Figure 4 and 5 frequency spectrum results, using Standards ISO 140 series and ISO 10052 (with 1/3 octave band measurements) are compared. Some differences are visible at low and high frequencies. This has not been observed for facade measurements.
In situ comparison for equipment noise On 29 in situ equipment noise measurements (WC flush and sink draining) a comparison between ISO 16032 engineering method and ISO 10052 survey method has been performed. The main features of survey method are the following: - only overall levels are considered; - no correction for background noise is applied; - correction for reverberation time is applied globally; - no corner selection procedure is needed (corner position should be chosen close to the apparent corner with the acoustically hardest surfaces, preferably in a distance of 0.5 m from the walls); - only two microphone positions are needed, one in a corner and one in diffuse field. According to ISO 16032 measurement repetition number, in each microphone position depend on the difference on the overall A-weighted levels between two consecutive corner measurements. Furthermore two measurements diffuse field position are required. So, with the precision standard, more than one measurement has been done in each microphone position. The same measurements have been used to calculate equipment noise with the two standard but for the survey method only two measurements are required. Consequently, from ISO 16032 measurements set, two measurements, one in the corner and one in a diffuse field position, have been selected. In order to find the maximum deviation between the two standards, the following measurements have been used for ISO 10052 calculations: - the maximum A-weighted level of corner measurements and the maximum of diffuse field measurements; - the minimum A-weighted level of corner measurements and the minimum of diffuse field measurements.
Figure 4: Comparison of frequency results using ISO 1404 and ISO 10052 for the same airborne measurement
Differences between results calculated with ISO 16032 and ISO 10052 (using maximum and minimum levels) are shown in Figure 6: these are the maximum deviations due to the different number of measurements prescribed in the two standards.
Figure 5: Comparison of frequency results using ISO 1407 and ISO 10052 for the same impact measurement
Figure 6: Differences between ISO 16032 results and minimum and maximum levels obtained using ISO 10052
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AIA-DAGA 2013 Merano On the other hand, using the same number of measurements for the two methods calculations, the differences between the two standard results is nearly null: this means that to make calculation in frequency band or using overall levels do not lead to significant differences and also the background noise correction is not relevant. This last statement is not always true for is referred to this measurement campaign because all the equipment tested were mounted on heavy building structures. Using the same number of measurements for the two methods and applying also the reverberation time correction, a little difference is notable (0.23 dB averaging on 29 measurement). This means that there is a little difference in the use of reverberation time correction in every frequency band or globally. The use of standard ISO 10052 for equipment noise is particularly useful respect to standard ISO 16032 cause time needed for measurements and calculations is significantly lower. So it is important to know that the use of the survey standard lead to reliable results. To decrease the uncertainty of survey standard the number of measurement positions and measurements should be increased, maintaining the use of overall levels.
In order to be able to compare also frequency spectrum results, ISO 10052 standard has been used with 1/3 octave bands measurements instead than with octave bands. The frequency raged used for all methods was from 50 to 5000 Hz, but without any additional care for low frequency measurements. The average results of different teams are shown in Figure 8 for airborne measurements and in Figure 9 for impact measurements. Black columns refer to engineering method results and the grey ones to ISO 10052 results. The two lines indicates the average values calculated over all laboratories. The difference between the two methods average results is of 0.5 dB for impact measurements and of 0.4 dB for airborne measurements. The comparison of repeatability results of the two standard are shown in Figure 10 for airborne measurements and in Figure 11 for impact measurements. Reproducibility results are shown in Figure 12 for airborne measurements and in Figure 13 for impact measurements. 58 57
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Interlaboratory test for airborne and impact sound insulation
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In order to know the accuracy of ISO 10052 method, for airborne and impact measurements, respect to ISO 140 part 4 and 7 standard, an interlaboratory test has been organized.
11 teams took part to the interlaboratory experiment and 5 repetitions of each measurements were performer. Airborne and impact tests were made both with ISO 140 part 4 and 7 standard and with ISO 10052 standard. The engineering method has been used with fixed microphone positions and the survey method with the manually moving technique (operator holding by hand the sound level meter).
Figure 7: sketch of laboratory used for the Interlaboratory test. Partitions examined are highlighted
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Figure 8: Interlaboratory results for airborne measurements 95 94
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The test location was a private laboratory with coupled room for airborne test on walls and impact test on floor covering. Measurements have been organized in order to keep constant the receiving room. The building elements analyzed were a bare beam and clay block floor and a 12 cm hollow brick wall, lined with plasterboard on one side.
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Figure 9: Interlaboratory results for impact measurements
Figure 10: Repeatability results for airborne measurements
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AIA-DAGA 2013 Merano Hz only for ISO 140-7 measurements. However some abnormal values at low frequencies could be expected seen that no additional care for low frequency measurements have been taken. Looking at frequency spectrum results (averaged over all teams) the same deviations between the two standards at low and high frequencies occurred in the in situ campaign. At low frequency the spreads between the two methods results may be due to the non diffusivity of sound field: probably the manually moving technique, using only one position in the room center, do not sample enough the sound field. At high frequencies the differences between engineering and survey method can be due to the operator presence near the microphone or the movement of the microphone itself.
Figure 11: Repeatability results for impact measurements
Figure 12: Reproducibility results for airborne measurements Figure 15: Interlaboratory mean results for the impact measurement
Conclusion and further works The use of ISO 10052 survey methods have shown a good agreement with engineering method results except for frequency values in the extremes of the frequency range. However differences in the single number values are narrow. Also regard equipment noise the overall levels with engineering and survey methods are very close, using the same number of measurements. Also for equipment noise is necessary to compare the accuracy of the two standard, ISO 10052 and ISO 16032. For this reason an interlaboratory test on equipment noise, measured with both standards has been organised and is now in progress.
Figure 13: Reproducibility results for impact measurements
References [1] Pontarollo, C. M., Di Bella, A., Ruggeri, P., Granzotto, N.: Comparison between manually moving microphone technique and standard method in field measurements, performed according to ISO 140 part 4, 5 and 7. Proceedings of EUROREGIO 2010, Ljubljana, Slovenia. [2] Di Bella, A., Pontarollo, C.M.: Comparison of Uncertainties in Acoustic Measurements in Building with Different Test Methods. Proceedings of Forum Acusticum 2011, Aalborg, Denmark.
Figure 14: Interlaboratory mean results for the airborne measurement
The repeatability and reproducibility values are similar for the engineering and survey methods. Reproducibility shows a peak at 50 Hz, in the case of airborne measurements, for both methods; for impact measurements there is a peak at 63
[3] Di Bella, A., Pontarollo, C.M.: Noise from water installations: measurement problems in residential buildings with heavy structures Proceedings EURONOISE 2012, Prague, Czech Republic.
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