Vehicle Interior Noise Prediction by Using Experimental Methods and Analysis - Thesis Example

Figure 3.3 gives a summary of the coefficients of the fibre C1 results. It can be seen that the 2mm thick sample C1 has the lowest absorption at all, the frequencies. Double 10mm has the highest absorption when we consider only a frequency of up to about 2000Hz beyond which it is seen that the other samples have higher absorption except for the C1 sample whose absorption remains low through the experiment range frequency. In can also be seen that when we consider the frequency of up to 2000Hz the absorption from highest to lowest is double 10mm, double 5mm, 10mm, double 2mm, 5mm and then 2mm.Figure 3.3: C2 absorption coefficients curves 4.

2 Fibre C2 results 4.2.1 Absorption coefficient for single fibre C2 Figure 3.4 shows the absorption coefficient for fibre C 2 for three different thickness starting from 2mm (C2), 5mm and 10mm thickness. From the figure, it can be observed that the experimental values were higher than the simulated values for all the frequency range investigated. It can also be seen that as the sample becomes thicker the experimental results curve become smoother and that the deviation between experimental curves and simulated results curves become smaller.

  From the graphs it can be seen that for the 2mm sample the maximum absorption of close to 1 is reached at a frequency of about 5500Hz, for 5mm sample maximum is reached at about 2500Hz while in the 10mm maximum absorption of close to 1 is reached at about 2000Hz frequency.Figure 3.5: Absorption coefficient for single fibre C2 curves 4.2.2 Absorption coefficients for Double C2Figure 3.2 shows the results that involved using two pieces (double) of the fibre C1 sample.

The samples used in the three set up were 2mm, 5mm and 10mm respectively. From the first pair of graphs, it can be seen that the experimental values rose to a maximum of about 0.95 when the frequency rose to about 4500Hz. 

In the case of Double 5mm the maximum about of about 0.90 was at about 2500Hz . For double 10mm the maximum absorption value is seen to low also at about 0.90 and arrived at a frequency of about 1800Hz. Figure 3.2 : Absorption coefficients for Double C1 curves 4.1.3 Comparison of C2 absorption coefficients Figure 3.3 gives the summary of the coefficients of the fibre C1 results. It can be seen that the 2mm thick sample C1 has the lowest absorption at all, the frequencies. Double 10mm has the highest absorption when we consider only a frequency of up to about 2000Hz beyond which it is seen that the other samples have higher absorption except for the C1 sample whose absorption remains low through the experiment range frequency.

In can also be seen that when we consider frequency of up to 2000Hz the absorption from highest to lowest is double 10mm, double 5mm , 10mm , double 2mm , 5mm and then 2mm. Figure 3.3: C2 absorption coefficients curves 4.2 Fibre C2 results 4.2.1 Absorption coefficient for single fibre C2 Figure 3.4 shows the absorption coefficient for fibre C 2 for three different thickness starting from 2mm (C2), 5mm and 10mm thickness. From the figure it can be observed that the experimental values were higher than the simulated values for all the frequency range investigated.

It can also be seen that as the sample becomes thicker the experimental results curve become smoother and that the deviation between experimental curves and simulated results curves become smaller. From the graphs it can be seen that for the 2mm sample the maximum absorption of close to 1 is reached at a frequency of about 5500Hz, for 5mm sample maximum is reached at about 2500Hz while in the 10mm maximum absorption of close to 1 is reached at about 2000Hz frequency. Figure 3.5: Absorption coefficient for single fibre C2 curves 4.2.2 Absorption coefficients for Double C2 Figure 3.

2 shows the results that involved using two pieces (double) of the fibre C1 sample. The samples used in the three set up were 2mm, 5mm and 10mm respectively. From the first pair of graphs it can be seen that the experimental values rose to a maximum of about 0.95 when the frequency rose to about 4500Hz. In the case of Double 5mm the maximum about of about 0.90 was at about 2500Hz. for double 10mm the maximum absorption value is seen to low also at about 0.90 and arrived at a frequency of about 1800Hz.

Figure 3.6 : Absorption coefficients for Double C2 curves 4.2.3 Comparison of C2 absorption coefficients In figure 3.7 the results of summary of the coefficients of the fibre C2 are given. It can be seen that the 2mm thick sample has the lowest absorption considering all frequencies. Double 10mm has the highest absorption when we consider only a frequency of up to about 1300Hz beyond which it is seen that the other samples start having higher frequency and at about 4000Hz the double 10mm has the lowest absorption.

In can also be seen that when we consider frequency of up to 1300Hz the absorption from highest to lowest is double 10mm, double 5mm , 10mm , double 2mm , 5mm and then 2mm. Figure 3.7: C2 absorption coefficients curves 4.3 Fibre C3 results 4.3.1 Absorption coefficient for single fibre C3 Figure 3.4 shows the absorption coefficient for fibre C 3 for samples with thickness from 2mm (C2) , 5mm and 10mm . It can be seen that the experimental values are above the simulated values. The experimental values for 2mm sample are more erratic than in the other two samples where curves are much smooth.

It can be seen that the maximum absorption is achieved at a much high frequency of well over 6000Hz while in the 5mm and 10mm sample maximum absorption is at a lower frequencies of about 2500Hz and 2000Hz respectively. Generally there is close match of simulated and experimental results. Figure 3.8: Absorption coefficient for single fibre C3 curves 4.3.2 Absorption coefficients for Double C3 Figure 3.9 shows the results that involved using two pieces (double) of the fibre C3 sample.