The Limits of Acoustic Levitation

When we use sound, it's a bit more tricky because you need to create something that is called like a hollow trap. And again, you do something with the waves so that that silent core moves towards the source. So what is the current limits of this then? How large of an object can you move with this sort of acoustic levitation? There are two limits. One is how dense the object can be and that depends on the power that you put on the sound. The other limit depends on the wavelength of the sound that you use - basically objects cannot be larger than half of the wavelength. But I think people usually get disappointed because they say 'can you levitate a car?'