Boston — Give advertisers a half-minute, and sure enough, they'll give you 34 seconds worth of sales pitch.
At least that seems to be one idea behind time compression -- a controversial technique that lets advertisers speed up commercials without making people in them sound like overwrought chipmunks.
It's done with the help of a minicomputer that electronically lifts out blank space within and between words on a recording, leaving the pitch of the human voice virtually untouched. The technique can be used on voice recordings, and also on film and videotaped programs (by slightly speeding up the action to synchronize with the ''compressed'' sound track). As a result, advertisers are able to tuck more information into commercials.
Broadcasters sometimes use it to tailor radio and television shows to fit into programming slots. For instance, the movie ''Chinatown'' was 14 minutes too long to fit the network schedule. So instead of editing, CBS simply time-compressed the film 10 percent. Many broadcasters generally don't employ time compression because it degrades video quality -- giving a slight jerkiness to motion shots.
''It's not something somebody's trying to do to brainwash you,'' says Nelson Funk, president of Rodel Audio in Washington, D.C. ''It's a device for getting more words into a minute, which in the commercial business is a real joy and treat.''
Mr. Funk figures his company uses time compression on about 10 percent of its production projects, ranging from radio advertising for used-car lots to campaigning politicians.
Meanwhile, it's hard to say just how many commercials are now being time-compressed. Many advertisers say they don't like to use the equipment, because it ''reflects sloppy work.'' But other experts say it's more common than you might suspect.
''There are a lot of well-known commercials that have been through time compression,'' says James MacLachlan, an associate professor of management at Rensselaer Polytechnic Institute who has studied the impact of compressed commercials on audiences. ''Eighteen of the top 20 agencies have used the process that I know of,'' he adds.
Questions have been raised about the impact time compression has on individual viewers. Studies conducted by Professor MacLachlan suggest there may be a link between time compression and the amount of information a listener retains.
''If the spokesperson doesn't . . . present the information at a reasonably brisk pace,'' says MacLachlan, ''it's very easy for your attention to wander, particularly in the case of TV commercials - where you can anticipate the message.''
Another subtle effect of time compression may be to increase the humor level in situation comedies. ''We aren't doing any of it for broadcast now,'' says Dick Mulliner, manager of post-production at ABC-TV. But the network has looked into the idea of compressing sitcoms. And the faster pace does seem to give the shows more spunk, he says.
Advertising agencies, meanwhile, say they don't use time compression to manipulate consumers, but to fix up botched work -- such as a 30-second commercial that runs 34 seconds.
''Whether the ability to put more selling points in a commercial makes it more effective is open to question,'' says a spokesman for one major New York advertising agency who asked not to be identified. ''We're not sure the retention rate with time compression is really any better.''
But even industry insiders admit this time-tampering technology has the potential for abuse, such as over-compressing commercials to the point that they begin to annoy viewers.
''There's always going to be some outfit that abuses it,'' says Mike Klasco, research and development director for Integrated Sound Systems, which builds time-compression equipment. ''There's a point where you go faster and it gets more interesting. And then if you go even faster, it gets to be too much,'' he notes.
For now, it appears only a few advertisers write longer commercials with the intention of compressing them later. ''People are talking to us about it,'' says Geoff Kelly, vice-president for sales at Teletronix, a New York post-production house that time-compresses commercials and feature movies. ''But they're not actually willing to go out and do it.''
One problem, Mr. Kelly says, is that TV networks may get riled if advertisers start routinely cramming additional seconds worth of information into standard-length commercials.
There are also ethical concerns. For instance, a time-compressed commercial showing a cleaner being dropped on a stain might make the product look as if it works better or faster than it really does. In the 1960s, the Federal Trade Commission dealt with a case in which TV demonstrations were speeded up, and decided they were misleading.
But some of the difficulties with time compression aren't so clear-cut, says Mr. MacLachlan, who launched a company that specializes in time-compressing commercials.
''I was asked to time-compress some politicians, and I felt in this case the politicians were the product,'' he says. He turned down the client, he adds, because he decided it misrepresented the product to make politicians seem more smooth-tongued than they are.
And yet, Rodel Audio's Mr. Funk doesn't seem to have similar qualms about compressing political commercials.
''In many cases where you've got a candidate that doesn't sound like too interesting a guy, just compressing him will make him sound a little more coherent and gives him a little more vitality,'' says Mr. Funk.