Hooray for Li Na, whose defeat of Maria Sharapova yesterday guarantees that there will be relative quiet from at least one end of the court in the Australian Open women’s final tomorrow night.

Her opponent, Victoria Azarenka, lets out a long, agonised shriek every time she hits the ball. It begins with her backswing, increases at the point of impact, then lingers at sustained volume almost until the person across the net gets to takes a swipe.

Azarenka’s vocal histrionics are far from unique. Female players who don’t grunt loudly with every shot are now a rarity. Channel Seven can have fun with their shriek meter decibel count, but the gimmick hides a nasty truth of the modern game: grunting during a point is cheating, pure and simple.

Here’s the applicable International Tennis Federation rule:

“26. HINDRANCE If a player is hindered in playing the point by a deliberate act of the opponents(s), the player shall win the point.”

Note: win the point. No let. No warning.

The key word in that rule is “deliberate”. The players who grunt and their defenders argue that all the noise is just an involuntary physical response to the exertion of hitting the ball.

Yet a generation ago — before Chris Evert and Monica Seles were allowed to establish the habit — none of the top players felt compelled to grunt like rutting elks. There are still plenty of competitors (most notably Roger Federer) who seem able to win umpteen Grand Slams without bellowing to the bleachers with every hit.

And the full-throttle swings of golfers, cricket batsmen and baseball hitters — all of which require at least as much physical effort as a tennis ground-stroke — can apparently be executed without the athlete emitting so much as a peep. In any case, the “involuntary” excuse is already covered in ITF Rule 26:

“The point shall be replayed if a player is hindered in playing the point by either an unintentional act of the opponent(s), or something outside the player’s own control.”

In other words, a player who objected to the distracting noise coming from the other end of the court could ask that the previous point be replayed, again and again, until their opponent desisted, retired or was defaulted.

Loud, prolonged vocalising during a point is cheating not just because it is a distraction, but because it also robs the opponent of crucial sensory information.

As any bat-and-ball sport participant knows, the precise timing and sound of the ball strike and bounce provide vital cues as to spin, strength of shot, and speed and height off the ground. If these are masked by any additional sound then you are robbed of information that helps fashion the best response.

Imagine, in cricket, a bowler yelling out loudly during delivery to cover the sound of a bouncer hitting the pitch so that the batsmen then has trouble picking up the flight of the ball. Same effect.

In tennis, the grunt does nothing to improve the grunter’s shot, but potentially does plenty to handicap their competitor. Which is why so many players grunt for so long and loud. And it’s not just the female tennis players who indulge — Jimmy Connors and Rafael Nadal have been known to grunt.

It’s a form of cheating so endemic that the Women’s Tennis Association last year announced a tepid set of proposals aimed at diminishing the practice (but without penalising current offenders). Pure PR, with no discernible result.

So why has this so far gone unpunished? Because the players are now so rich and powerful that they run the sport.

Central umpires could stamp out the practice forever by applying the “hindrance” rule at the next Grand Slam tournament. But they are employed as part of the tour, and are all too concerned for their jobs to take any direct action on themselves.

Where is Darrell Hair when you need him?