Can i say "Hearsay hangs in the air?"

well, you could; but you'd probably be the first person in all the known universe to do so. (I'm saying it this way in the hopes that we'll get some context for one of these odd questions.)

Hearsay refers to allegations picked up from gossip. The buzz,buzz of busy gossipers hangs in
the air of a crowded meeting. But 'hearsay" is an abstraction, and has the implication that
whoever reports it may well distort it. That's why it is inadmissible in legal proceedings.

Again, suededevil, I enjoy your questions, and hope you will ask lots of them.

I think it's a very nice metaphor. I would take it to mean that there are a lot of opinions about, all loosely based on fact. A lot of people are talking about something without really knowing what they're talking about. There are overtones of ominousness in it.

I like the phrase, I must say, sue

but There are overtones of ominousness in it.
reminds me that, in C17 Britain, thieves and murderers used to hang in the air - sometimes from a week or two, as an example to others!

And the Bulwer-Lytton goes to:

There was the palpable crackle of tension in the stadium and cries of shame rent the air, as the wretched prisoners were dragged into the arena, in front of an audience too busy with the macabre revelries to notice the thick, low slung cloud of hearsay ominously hanging over their drooping heads.

...in C17 Britain, thieves and murderers used to hang in the air - sometimes from a week or two, as an example to others!

At least they were theives and murderers. It reminds me of a song Billie Holliday sung from back in '38 titled "Strange Fruit".

Abel Meeropol, a white Jewish teacher in a New York City high school, wrote the lyrics and music of "Strange Fruit," and shared the piece with Billie Holiday in 1939 when she was singing at Cafe Society, the leading left-wing, integrated night club in Greenwich Village. Meeropol was a political activist, a member of the Communist Party, and after the execution of Julius and Ethel Rosenburg raised their orphaned children. "Strange Fruit" soon became the opening song for Holiday's sets and a popular success when she recorded it. The searing lyrics often upset club patrons and it became a weapon in continuing anti-lynching campaigns. Meeropol must have been surprised, but pleased at the song's impact. In an interview in 1971 he commented: "I wrote 'Strange Fruit' because I hate lynching, and I hate injustice, and I hate the people who perpetuate it."

http://womhist.binghamton.edu/aswpl/doc1.htm