Why do gay men sound like a "pack of braying ninnies"? That's the rather brutal question at the heart of David Thorpe's documentary Do I Sound Gay?, screening as part of the Melbourne International Film Festival, which kicks off on Thursday night.

If you think the question sounds a touch homophobic, you'd be right. But as a gay man, Thorpe is perhaps more entitled than most to ask it – of himself as well as his friends, linguists, voice coaches and others.

This is Thorpe's first film and it was, he says, "first and foremost a personal project". He started on it five years ago, freshly single and full of the questions people often ask themselves at the end of a failed relationship – top of the list being "what's wrong with me?"

For Thorpe, the answer was "my voice".

"The loathing of the voice is the last vestige of internalised homophobia," the 45-year-old New Yorker says.

"Self-loathing is a concept every gay man is familiar with. You don't just snap your fingers and accept yourself when you come out."

Thorpe says the moment he realised he couldn't bear the sound of the gay voice – he was on a train full of gay men heading to the beach for a weekend – was "a red flag to me that I wasn't really as out, loud and proud as I thought I was".

As it happens, Thorpe's journey to out-loud-and-proudness began in Australia, where he travelled in his gap year. Aged 19, he took the mail truck from Coober Pedy​ to Oodnadatta, and spent six weeks working on a ranch alongside Aboriginal stockmen, herding cattle on dirt bikes and shooting rogue camels. "I was trying to do the most macho thing I could," he says. "At the time I was still doing my fair imitation of a straight man, and my American accent was an additional disguise."

But it was here that he finally decided to come out, in a letter written to his best friend back home. "I'd had to go to the other side of the world, as far as I could get from home, to have the guts to write that letter," he says. "I sometimes feel like I was 'born' there, because it marked the beginning of my journey out of the closet into the real world."

That journey hasn't been without bumps, though, as Do I Sound Gay? makes clear. And personal though it is, Thorpe's film makes a convincing argument – through interviews with the likes of writer David Sedaris, Star Trek actor George Takei, gay activist Dan Savage and others – that plenty of others feel the same way about the gay voice.

Speaking of which, does it even exist? The film is a little equivocal on that, suggesting that while there is clearly a "gay-sounding voice" not all gay men have it, and many straight men do.

For all the hand-wringing, Thorpe is convinced that the stigma around the voice that fuelled his self-loathing is abating.

"I think we'll have a greater diversity of voices moving forward," he says. "I think there will be more people sounding 'gay', because the millennials and the YouTube generation value individuality more, they are much more comfortable with diversity, they grew up knowing gay people, trans people, people of all races."

Is it feasible that one day, perhaps, there might be a President of the United States who wakes up and asks himself 'Do I sound gay?', and is completely OK with it if the answer is yes?

"I don't know if Liberace could be President," he says, "but someone a little further back from that might be OK. But you never know."

Do I Sound Gay? screens on July 31 and August 13. Full program at miff.com.au. The Age is a media partner of the Melbourne International Film Festival.

Do you sound gay?

Well, you might if...

• You use clearer vowels than a typical male speaker
• Your vowel duration is longer
• Your Ss are longer (not the same as having a lisp, which is not, contrary to the stereotype, a marker of the 'gay' voice)
• Your Ls are clearer
• Your Ps, Ts and Ks are over-articulated

These are the markers of the "gay-sounding voice" as described by Professor Ron Smyth, linguist, University of Toronto, who researches the impact of sexual orientation on speech sounds. In a test in which 46 speakers were identified as gay or straight on the basis of their speech patterns, he claims that 25 participants scored about 60 per cent accuracy, suggesting the voice was a seriously unreliable indicator of sexual orientation.

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