Target-detection and localization in multilayered media through mixed TR–RTM method

Figures & data

Figure 1. Schematic diagram of three layers in layered media.

Figure 2. Signals received by the array element for (a) case 1, (b) case 2, and (c) case 3.

Table 1. Parameters of the layered media.

Medium	Material	Velocity (m s^–1)	Density (kg m^–3)	Thickness (mm)
Upper medium 1	Silicone rubber	1070	1096	50
Upper medium 2	Gelatin	1470	1047	50
Lower medium 1	Water	1500	1000	–

Figure 3. SIR for different emitter–receiver pairs at $S_1$ interface for (a) case 1, (c) case 2, and (e) case 3, at $S_2$ interface for (b) case 1, (d) case 2, and (f) case 3, respectively.

Figure 4. Results of the TR–RTM process for two interface-reflected signals (a) S1 and (b) S₂ in case 2.

Figure 5. Acoustic field (a) distribution map of the target signal in case 2.

Table 2. Comparison of the measured and actual target positions.

Case	Actual position (x, z)	Measured position (x, z)
Case 1	20 mm, 35 mm	20.9, 34.8 mm
Case 2	20 mm, 70 mm	19.3, 68.8 mm
Case 3	20 mm, 120 mm	19.4, 118.3 mm

Figure 6. Results of the TR–RTM process of the target in the first layer medium in case 1. (a) The acoustic field distribution for the target signal. (b) and (c) the acoustic field distribution of interface S₁ and interface S₂, respectively.

Figure 7. Results of the TR–RTM process of the target in the first layer medium. (a) and (b) the acoustic field distribution of interface $S_1$ and interface $S_2$, respectively, and (c) the acoustic field distribution for the target signal.

Table 3. Signal-to-interference ratio (SIR) of target signal and interface reflection interference signal.

		Before processing	After processing	Multiple of increase
Case 1	Upper interface s1	1.1	7.6	6.3
	Lower interface s2	2.2	24.8	11.3
Case 2	Upper interface s1	1.0	4.2	4.2
	Lower interface s2	17.9	120.5	6.7
Case 3	Upper interface s1	0.4	2.1	5.3
	Lower interface s2	3.9	32.1	8.2