HARDLY A DAY or an hour seems to pass any more without some momentous annoucement concerning defense policy - NATO, underground nuclear testing, the SALT talks, the Pentagon budget, the spread of nuclear weapons, the draft. What does it all mean? Our provisional answer is: Not nearly as much as you might think - at least not yet. These are the sounds of a new administration settling into office.

Still, the sounds can have consequences, especially if they issue from the President himself. If we know anything, it is that Mr. Carter is determined to arrest the spread of nuclear weapons to countries that don't have them and to reach arms control and reduction agreements with countries that do. He seems more preoccupied with these questions than any of his recent predecessors was, and that is good. His statements on the subject, however, have retained a certain campaign-ish quality that has left him open to challenge. How do you negotiate a complete ban on underground nuclear testing with the Russians so long as the Russians insist on pursuing so-called "peaceful" nuclear explosions underground, treaty or no? What does the new President mean when he says that he won't let the U.S.-Soviet conflict over their Backfire bomber and our cruise missiles "stand in the way of some [SALT II] agreement"? Strictly in terms of the bargaining to come, has he already unilaterally given away too much with that statement?

Since we are in favor of very nearly every arms control and antiproliferation measure Jimmy Carter has espoused, we sympathize not with his goals but also with his new dilemma. As the comedian Chevy Chase might sum up that dilemma: He is President and we are not - meaning that he now has the onerous and unaccustomed duty (of which the rest of us are blissfully free) of reconciling those sometimes conflicting goals with each other; and he must also try to bring them about in the face of foreign and domestic opposition, which is nothing you need to take much account of in a campaign pledge.

If fact, we believe the rhetorical fervor of Mr. Carter's early days in the White House has served a purpose: It has put people on notice that he is serious about wanting to do these things - government officials who might have had doubts about his commitment to arms control agreements, for instance, or allies who may have questioned the seriousness of his intention to reduce sales of dangerous nuclear materials to would-be bomb-making countries. But that is mood music, not policy. With the SALT I interim accord on offensive weapons due to run out this year, with important decisions needing to be made fairly shortly on defense investments, with the NATO forces sorely in need of revitalization, with ever more serious questions being raised about the efficacy of the all-volunteer army, and with the clock running on our capacity to do anything about the spread of nuclear weapons to certain countries, Mr. Carter now faces deadlines for action all across the board.

It will have struck you that these are not matters a government can deal with along lines made familiar by a Chinese menu - one from rom A, and two from row B. They must all be confronted and confronted in relation to each other . So we wouldn't look too hard for precise portents in the messages that have been coming out of the administration on these subjects in the past week. About all it adds up to so far is an earnest and welcome statement of intent to devise - and ultimately to execute - a comprehensive policy on defense and arms control.