## 2 Materials and Methods  
In the paper, SJA with nine different orifices were investigated. The first orifice was referenced and the orifice diameter was 20 mm and length 40 mm. The remaining was made based on the referenced orifice and differed in the number of chevrons. The chevrons were isosceles triangles with the same base and height length. In case \"a\", the orifices were classic chevron orifice and in case \"b\" the top of cutouts was rounded with a radius equal to R = 1/6 h--both types of the orifices were presented in Figure 2. The actuator with reference orifice was tagged as a case 0, and the next orifices were marked with consecutive numbers. The dimensions of the orifices were presented in Table 1. The orifices were printed in 3D technology from PETG (polyethylene terephthalate glycol-modified).  
The orifices were fixed with a four screw to the actuator body made from PMMA. The actuator body has a high of 20 mm and a diameter of 150 mm. The loudspeaker STH M.18.200.8.MCX was used. The same actuator but with other orifices was used in [29].  
The actuator was supplied with sinusoidal signals generated by a Rigol DG4162 waveform generator and strung by an AUNA CD-708 amplifier. The effective voltage and effective current were measured with a Keithley 2701 mm instrument (6.5 digits, 22-bit) with a 7706 all-in-one I/O module. To the current measurements was used additionally a reference resistor (1 \(\Omega\), 0.01%)- as was presented in Figure 3.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & \(d\) [mm] & \(l\) [mm] & **Number of Chevrons** & \(h\) [mm] & \(R\) [mm] \\ \hline Case 0 & 20 & 40 & - & - & - \\ \hline Case 1a & 20 & 40 & 4 & 18.85 & - \\ \hline Case 1b & 20 & 40 & 4 & 18.85 & 3.14 \\ \hline Case 2a & 20 & 40 & 7 & 10.77 & - \\ \hline Case 2b & 20 & 40 & 7 & 10.77 & 1.80 \\ \hline Case 3a & 20 & 40 & 10 & 7.54 & - \\ \hline Case 3b & 20 & 40 & 10 & 7.54 & 1.26 \\ \hline Case 4a & 20 & 40 & 14 & 5.39 & - \\ \hline Case 4b & 20 & 40 & 14 & 5.39 & 0.90 \\ \hline Case 5 [29] & 20 & 40 & 7 & 15.6 & - \\ \hline Case 6 [29] & 20 & 40 & 7 & 20.8 & - \\ \hline \end{tabular}
\end{table}
Table 1: Dimensions and parameters of SJA orifices.  
Figure 2: Schema of orifice.  
The parameters of SJ were measured with the time-mean reaction force method described by [PERSON] [34]. For this reason, SJA was measured with precision balance RADWAG WTC2000. The resolution of this device was 0.01 g, and the range was 2000 g. The SPL was measured with IEC 61672-1 Class 2 standard equipped with a 1/2 microphone. The measuring range was 35-130 dB (A) in a frequency range of 20-8000 Hz. The sound meter was located 1 m from the test stand. The background SPL of the environment was confirmed to be at least 10 dB lower than the SPL generated by the SJA. Type A frequency weighting was applied to the SPL measurements--SPL (A). The SPL was measured according to ISO 3746:2010 [35]. The same measurements method was used in [36; 37; 31].  
Atmospheric pressure was measured using a Honeywell HPB200W2 DA-B barometer, with an accuracy of \(\pm\)40 Pa. All devices were controlled using LabVIEW software with the National Instruments NI-USB-6211 card. All devices and their connections were presented in Figure 3. The measurements uncertainty was presented in Table 2.