It is plausible even without considering the supernatural.
Fluid
We do not know about the Bacta fluid, though. So it is hard to be exact. Let's assume it is at least like water or maybe more viscous. As a rule of thumb you can say, the more viscous a fluid is the better it can transmit vibrations, aka sound.
Tank
The tank itself is probably made of glass. A hard material with a crystalline atomic structure. Also it is transparent, which is not only nice for light to pass through, it is also an indicator that it is able to transmit vibrations (sound) well.
Dampening
In both cases the sound may not be transmitted in exact form. Some degree of dampening or dispersion will occur. Also the sound maybe skewed or even certain frequencies are fully absorbed.
Given the small size of the tank, I would argue that those effects are not strong enough to dissipate the sound beyond recognition.
A beneficial effect also is, that the fluid seems to be perfectly in rest. No waves or other turmoil, no bubbles, that might disturb the sound paths.
Real World Examples
There are a few ways to give a little proof to the concept that glass and a fluid like water allow for sound transmitting into the tank:
Just put on your ear on the glass window and check for yourself how much of the sounds you are able to hear from the outside. In my experience this is plenty and far louder than you would expect. In most cases you will hear cars passing by though. That is of course just noise.
Ever had some noisy neighbors chatting in front of your (closed) window? It is not a problem to discern words and whole sentences even if being on the other side of the room (given there is not much else noise, as cars passing by).
There are laser microphones, which are able to use a window as measuring surface to be able to eavesdrop spoken words inside the room (The article mentions an infrared beam used by the Buran eavesdropping device in case of glass windows).
Fill a bathtub with water, put up a music player outside, and submerge yourself carefully (try not to make waves). It is possible to listen to the music and not even too bad.
You can check out this video of Veritasium, where someone is submerged in a similar tank and holds his breath for 17 minutes. The relevant parts are at 15:00, 16:45 and 17:00 minutes, where he asks for the elapsed time (by signing), and the answer is given verbally to him, which he then acknowledges (by signing).