Proto-Indo European pronounciation

I have a question about PIE, how is *h₁, *h₂, *h₃ pronounced?

There isn't a clear consensus about it. See w:Laryngeal theory. Personally I think they were something like [h] or [x] for *h₁, [χ] for *h₂, and [xʷ] or [ɣʷ] for *h₃.