At These Decibels, the Audience Is Listening . . . and Shaking : Movies: Hollywood’s techno wizards are mastering the art of noise, creating soundtracks that are louder than life.

In an episode of the old “Batman” TV series, a villain ties Robin to the clapper of a giant clock bell. When the clock is to toll at midnight, the gonging is supposed to spell a particularly gruesome auditory doom for the Boy Wonder.

Not to suggest that the makers of “Batman Forever” have plotted the same fate for moviegoers, but if you see and hear the movie in the right theater, the experience can be akin to hanging out in that bell with the Caped Crusader’s hapless sidekick.

“You can feel the building shake at certain points,” says Stephen Rollins, 24, who had just seen the film at Mann’s Chinese in Hollywood for the third time its opening weekend. “The bass tones scream out as the vibrations hit you and shake you. It’s an awesome experience.”

“The sound is bigger than life,” says Rob Sterrett, 26. “It feels like it’s coming through the floor as well as from above.”

“Batman Forever,” which broke box-office records in its opening weekend, is hardly the only movie out there this summer that allows audiences to revel in the art of noise. Already in theaters is “Die Hard With a Vengeance,” which blows up huge chunks of New York City in eardrum-wobbling Dolby stereo, and “Congo,” offering killer monkeys getting ripped apart by laser guns while a volcano erupts. On the way: “Apollo 13,” which brings you up close and personal with a rocket’s liftoff, and “Judge Dredd,” which presents the grim future as, if nothing else, extremely loud.

Time for a quick listening lesson: Sound, measured in decibels, is first discernible to the human ear at roughly 20 decibels (roughly the sound of a feather brushing the ground). Normal conversation measures about 75 decibels, while conversations in movies--those on screen, not the loudmouthed louts sitting behind you--weighs in at 85 decibels. Noise can become harmful to the human ear at around 130 to 160 decibels if held for sustained periods. Movie cacophony at its loudest is designed to be played between 110 and 120 decibels, and then for only fractions of a second at a time.

Along with the Batmobile, the highest decibel reading in “Batman Forever” comes when Tommy Lee Jones, as Two-Face, shoots a gun in his lair and the bullet ricochets around the room, good enough for a momentary 115 on the decibel level. But that’s a high-end sound effect, not employing the gut-rumbling bass of Batman’s wheels.

“Before the digital world, before Dolby, such gunshots would snap the speakers,” says Peter Macgregor-Scott, producer of “Batman Forever.” “You could never get the full range, because the speaker couldn’t handle it.”

As an example of the work that goes into creating the perfect sound mix, Macgregor-Scott points out that to get the Batmobile to roar to life, “we used 60 separate tracks. Some of our guys went to Rocketdyne and said, ‘We’d love to record a jet engine.’ They said, ‘Sorry, we don’t permit film crews here.’ They replied that they were creating the sound for the Batmobile, and they said, ‘Come on in, boys!’ ”

Thanks to the low-end bass sound (or “boom,” as Macgregor-Scott calls it) of the jet noise of the Batmobile taking off, “You can physically feel the soundwaves surrounding your body. You’re in the car.”

To get Gotham City to sound its best, Macgregor-Scott brought in the team nominated for sound engineering Oscars on his previous productions, “The Fugitive” and “Under Siege.” He noted that the former had some incredibly elaborate sound effects. For the famous train crash sequence in that film, 240 separate sound-effects tracks, “four or five” dialogue tracks and 48 tracks of music were mixed together in a mere three minutes of film. “The Fugitive” employed a staff of 100 for the film’s sound; “Batman” used slightly fewer.

“We in the film business have historically been 15 years behind the record business in terms of audio sophistication,” says Dennis Maitland, a sound mixer on “Die Hard With a Vengeance” whose work has garnered him two Oscar nominations. “Now, we’re still behind, but we’re coming up in leaps and bounds.”

Technology has allowed sound mixers such as Maitland to capture even the quietest sounds amid the mayhem of an action film. While working on “Die Hard With a Vengeance,” Maitland offered to bet star Bruce Willis their respective homes that he could record logistically difficult scenes without needing to re-record any dialogue in post-production. Wisely, Willis declined the offer, because Maitland says he would have won.

Sound is mixed into the final soundtrack from three primary sources: what is recorded on the set, sound effects created in studios and the musical score. All of this is compressed into between two and eight tracks (the majority of the best theaters run six tracks) on the film’s soundtrack.

David MacMillan, sound mixer on “Apollo 13” and part of the Oscar-winning sound team of “Speed” (he had previously won an Academy Award for another space film, “The Right Stuff”), says he helped record some of the rocket takeoff effects with sound effects supervisor Donald Flick, working from tracks provided by astronaut Dave Scott, one of the film’s technical advisers.

“They were recorded by NASA, and we heard what taking off sounded like with a lot of noise the public doesn’t hear,” MacMillan says. “We actually matched or used parts of the tape to create the feeling of what it was like in the capsule itself.”

Ironically, the astronaut didn’t recall the sound of liftoff himself, MacMillan says. “I asked David, and the thing is, so much sound is so far behind them, they don’t notice it. In the initial stages of the liftoff, the noise is 100 yards away. Once you get past the speed of sound, the sound is far behind you.”

As much work goes into recording the sound of quieter films as the noisy blockbusters, MacMillan says. “It’s purely luck that you get on films [like “Speed”] that are recognized,” he says. “They always recognize the big splash. Seldom will you see subtle pictures get recognition. As my dad always said about music, ‘If you can’t be good, be loud.’

“The most difficult things are the [quiet] dramatic pieces,” he says. “All this equipment and ambient noise all around, and you have to record quiet, subtle dialogue. That’s the most difficult stuff.”

Still, all the effort that goes in to creating the soundtrack can be messed up by the theater’s sound system.

“We send theaters a reference tone that they can align their equipment to, but they can play it so low you can’t hear everything or so loud it’s irritating as hell,” Maitland says. “Sound works in an almost subliminal way--if you have difficulty understanding people on screen, the minute that happens, you’re out of the movie, out of the make-believe.”

“I saw ‘Speed’ twice last year, once in a good theater and once not,” MacMillan says. “The difference in the soundtrack is amazing. It’s pretty disappointing to hear a movie through a bad sound system. It makes you realize how most theater operators feel that sound is secondary, when it’s obviously part of the whole experience. It really pays to see a movie in a first-class theater.”

How to choose that first-class theater? There are three main formats: Dolby Stereo and Dolby Stereo Spectral Recording (SR), which play in two-track stereo; six-track Dolby Digital, often denoted as THX or DTS in newspaper ads; and Sony Dynamic Digital Sound (SDDS), which plays in both eight and six tracks.

According to Macgregor-Scott, SDDS can be the most dynamic, but few theaters can accommodate the eight-track format, so often the sound is automatically “folded down” into six. The most reliable, Macgregor-Scott says, is Dolby Digital, because it’s “true six-track, absolute perfection.”

The difference between a theater with a six-track Dolby Digital sound system and one with a two-track SR system, says Macgregor-Scott, “is like listening to a $20,000 stereo system down to a boombox.”

Also, the bigger the auditorium the better, though anything more than 300 seats will be fine. And, if you want to see a quieter movie, make sure it’s not playing in an 18-plex next to a blockbuster whose explosions will bleed through the walls.

Back at the Mann’s Chinese--which Macgregor-Scott says has the most powerful Dolby Digital system in the area--”Batman Forever” patrons are convinced.

“It vibrated--it made us jump,” says Nosbell Vivas, 13, who saw “Batman Forever” at the Mann’s Chinese. “I was almost deaf in the beginning.”