## 5 Results and Discussions  
The side-firing front chamber designs are manufactured by using a 3D printer, as shown in Figure 10a. Type 1, type 2, and type 3 have the same tube width and tube height but different tube lengths. Type 1, type 4, and type 5 have the same tube length and tube height but different tube widths, which causes the different tube areas, while type 1, type 6, and type 7 keep the same tube length and the same tube area controlled by the tube width and tube height. The microspeaker unit and different side-firing front chambers are assembled together, as shown in Figure 10b. An experimental SPL comparison between the different side-firing front chamber designs is shown in Figure 11. In the first group, the type 2 has biggest \(f_{HREC}\) and \(f_{TEC}\), and the frequency of mid-high frequency peaks sorted from big to small is type 2, type 1, type 3, as shown in Figure 11a. In the second group, all types' \(f_{TEC}\) are the same, while the \(f_{HREC}\) are different, and the frequency of mid frequency peaks sort from big to small is type 5, type 1, type 4, as shown in Figure 11b. In the last group, all types have the same mid-high frequency peaks even though they have different tube widths and tube lengths, as shown in Figure 11c. A mid-high peak frequencies comparison between the different prediction methods is presented in Table 3.  
According to the above results, the following conclusions are obtained:  
1. The longer tube length (the same tube area), the lower \(f_{HREC}\) and the lower \(f_{TEC}\). 2. A wider tube width (the same tube length) causes a higher \(f_{HREC}\) owing to the larger tube area. The tube width has a slight influence on \(f_{TEC}\) when the end correction is considered. 3. With different tube widths and tube heights (the same tube length), the \(f_{HREC}\) can be similar when the tube area remains the same. Figure 9: Different tube designs. The mid-high peak frequencies can be calculated according to the dimensions of the tube and cavity using method #1. However, it cannot predict the SPL result, whereas method #2 can predict the SPL results and mid-high peak frequencies well. The SPL comparisons between the experimental results and the E-M-A coupling analysis results are shown in Figure 12. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & \(f_{\text{{HREC}}}\) **(Method \#1/Method \#2/Expt.)** & \(f_{\text{{TEC}}}\) **(Method \#1/Method \#2/Expt.)** \\ \hline Type 1 & 3099/3150/3000 & 14,929/15,000/15,000 \\ \hline Type 2 & 3408/3350/3350 & 18,076/17,000/17,000 \\ \hline Type 3 & 2862/2800/2800 & 12,715/13,200/13,200 \\ \hline Type 4 & 2543/2650/2650 & 15,069/15,000/15,000 \\ \hline Type 5 & 3569/3350/3350 & 14,852/15,000/15,000 \\ \hline Type 6 & 3146/3150/3150 & 15,357/15,000/15,000 \\ \hline Type 7 & 3075/3000/3000 & 14,713/14,000/15,000 \\ \hline \end{tabular}
\end{table} 
Table 3: Peak frequencies comparison (All types). Figure 10: Different side-firing front chamber samples: (**a**) The side-firing chamber; (**b**) The different samples. Figure 11: Experimental SPL comparison: (**a**) type 1, type 2, and type 3; (**b**) type 1, type 4, and type 5; (**c**) type 1, type 5, and type 6. The microspeker has a frequency response curve with certain frequencies at which the sound pressure output is particularly strong. These frequencies may be perceived as being more \"loud\" or \"intense\" by the listener, and they may also be associated with specific types of sounds. The advantage of mid-high frequency peaks to the user may depend on the specific frequencies and intensities involved, as well as the listener's individual auditory perception and preferences. For example, if the peaks occur at frequencies that correspond to certain musical notes or other sounds that are important to the listener, then these peaks may be perceived as enhancing the overall quality or clarity of the audio output. On the other hand, if the peaks are too pronounced or occur at frequencies that are unpleasant or jarring to the listener, they may be perceived as a disadvantage.