Shots rang out at the John F. Kennedy assassination site yesterday morning as experts conducted a sophisticated test to determine how many shots were fired at the presidential motorcade on Nov. 22 1963.

The acoustical experts, called in by the House Assassinations Committee and employed by the same company that investigated the 18 1/2-minute Watergate tape gap, declined to comment on the results of their test here. The firm, Bolt, Veranek and Newman of Massachusetts, is expected to present its findings to the House panel next month.

It took more than four hours for three Dallas Police Department sharpshooters to fire 56 rounds of live ammunition into sandbags strategically placed along the motorcade route.

The police officers fired two Italian-made Mannlicher Carcaco rifles, identical to the one believed used by Lee Harvey Oswald, who was named by the Warren Commission as Kennedy's lone assassin. The officers fired from the sixth floor of the Texas School book Depository building, from the window where Oswald reportedly fired three shots at Kennedy.

Shots also were fired from a grassy knoll near the building with a .38-cal. Smith and Wesson revolver. The pistol was fired from behind the knoll, where some experts say a second assassin fired a fourth shot. Patrolman Tom Knight, who fired the revolver yesterday, would not comment on the reasons for its use. But it has been reported that the Jack Ruby pistol, delivered to the House panel last week, also was a .38-cal. revolver. (On Nov. 24, 1963, Ruby shot and fatally wounded Oswald.)

Yesterday's test were recorded by more than 50 microphones and the recordings were to be compared against a Dallas police tape recording of the original gunfire that seemed to indicate a fourth shot.

The testing attracted some 200 spectators, about half of them from the news media. They started gathering around police barricades at about 5:30 a.m. to watch the testing crewmen set up thir tripod-held microphones.

Almost an hour after daybreak, a policeman revved up his motorcycle to stimulate the traffic noise during the assassination, and the first shot was fired from the depository window into one of four piles of sandbags placed along the parad route. The shots reverberated in a clockwise echo, against the Dallas County records building to the left, and around the post office straight ahead.

As the shots rang out, many in the crowd seemed to shudder, startled.

A number of out-of-town bystanders interviewed yesterday seemed to think the reenactment was worthwhile, but to the few local spectators it was an unneccessary resurrection of a tragic incident that Dallas, still smarting from the brand "City of Hate," would prefer to forget.

Cab driver Geraldine Walker, who stood behind the barricades starting at dawn, put it his way:

"I hear a lot of negative attitudes toward Dallas from the people in my cab. They remember the way Adlai Stevenson was treated and they remember now Richardson [a Dallas suburb] has a hate campaign. I have people in my cab from all over the world, and this is the main thing they want to see."

"What's the purpose of it? I don't understand it." said Mary McCord of the reenactment. "It happened 13 years ago and people are still crying over it."

But spectators from other areas said the reenactment was worthwhile. "This should have been done a long time before." said John Ruiz, who came from Indiana for a Veterans of Foreign Wars convention here. Rick Bennett of Framingham, Mass., said he "just wanted to come down to make sure they did what they said they were going to do, or whether it was all a farce."

Even a non-English-speaking Venezualan military officer who was touring the John F. Kennedy Museum yesterday morning with his family agreed that restaging was valuable. "It is very important for us to know what happened," Lt. Col. Joseph Alvaroz said in Spanish. "This act is important."

But no conclusions were announced, and most spectators left bewildered. As the only patrolman at the scene who witnessed the assassination 15 years ago said, "I don't know what they can prove. It's still just as confusing now as it was then."