## 3 Results
### Analysis of the Delivered Acoustic Field  
The acoustic field in the culture dish was measured and modeled. Measurements were carried out with a wide-band hydrophone when the transducer was emitting a 10 sine-cycles tone-burst. Figure 3a shows the measured radiation pattern of ultrasound transmitted through the culture dish compared with the no-dish condition. The measured pattern for no-dish condition corresponds to a Bessel-like profile characteristic in the Fresnel-zone of no-backed planar transducers [21]. The acoustic field measured through the dish shows clear differences in shape from the no-dish condition. The field at the central zone of the culture dish presents a slight energy concentration of 7.8% (with a relative reduction at other more external zones) that could be influenced by wave reflections at the surface of the water that was agitated by the acoustic radiation force; this vibration was perceptible even with bare eyes and it was more intense at the center of the culture dish. This behavior is not replicated by the models since water agitation is not included.  
The modeled acoustic patterns at the surface of the water for the dish and no-dish conditions are shown in Figure 3b. The radiation profiles between the two conditions are similar at the central zone of the well with a slight variation at the border of the dish that can be also noticed in the measurements. The acoustic attenuation of the dish combined with 94% of the transmission coefficient at the two interfaces water-polystyrene [28] produces an average amplitude reduction of 9% that is congruent with measurements. The measured attenuation of the dish was 4.01 Np/m congruent with Table 1. Although the shape of the real field measured through the dish is modified by water vibration, the average pressure corresponds to the expected one, as verified by the models, with a small effect of attenuation and transmission losses.  
Standing waves produced by both parallel and inclined surfaces are analyzed for our setup. Parametric simulations varying _TD_ and _CM_ were carried out to determine the combinations of those distances that produce resonant fields. The average pressures at the surface for each parameter combination are shown in the 2D color plots of Figure 3c,d for the models with parallel and inclined boundaries, respectively. From the pattern of Figure 3c, standing waves increase the average pressure at the surface following the expected tendency, i.e., resonances are produced at distances that are multiples of half-wavelength of ultrasound in media. The observed pattern forms circle-like regions where the acoustic pressure is not increased, with a small central zone at half pressure amplitude that was produced by anti-resonant destructive interference. When the dish is inclined relatively to the transducer,\(\xi=2^{\circ}\) and \(\varphi=-1^{\circ}\), the resonances are importantly attenuated (Figure 3d). This reduction is mostly true when the dish and the transducer are individually rotated in the same direction (notice the opposite sign of the angles) to have at least \(1^{\circ}\) of relative inclination. Rotations at opposite directions (as the drawing of Figure 1c) produced mixed results showing either reduction or creation of standing waves at certain angles combinations (data not shown).