ONE OF THE ARGUMENTS often made against broadcasting sessions of Congress is that the intrusion of microphones and cameras would change the nature of the proceedings. It seems clear, after three days of radio coverage of the debate on the Panama Canal treaties, that the presence of microphones does change what happens on the Senate floor. But the change, at least so far as we can see, weighs heavily in favor of broadcasting.

The sound in the Senate last week was that of a debate. Real, live senators were on the floor to challenge statements made by their colleagues. The accuracy of "facts" was questioned, interpretations were disputed, points were scored. Speakers seldom were allowed to drone on endlessly; some had to fight off questioners to get their speeches completed. Even absent senators appeared to think the debate meant something. Many tuned in their offices.

Contrast that, if you will, with the sound of the Senate during some other historic "debates." All too often it has been the sound of a series of long and boring speeches listened to, as far as an observe could tell, by practically no one. Misstatements went unchallenged. Tourists went away shaking their heads at the Senate's claim to be "the world's greatest deliberative body."

Though we can't prove it, our suspicion is that the microphones made the debate. Neither supporters nor opponents of the treaties wanted any portion of the public to get a one-sided version of what the dispute is about. Thus, each side was making an effort to see that any argument was refuted as quickly as possible. And that, we submit, is just the point. Far from encouraging showboating, the microphones seemed to concentrate senatorial minds and create conditions conducive to spirited exchange of opposing views. By broadcasting this debate live, public radio is doing a service not just to the public but to the Senate as well.