Stilled voices for human rights in Latin America continue to be heard, however faintly. They are those of Orlando Letelier, the exiled Chilean diplomat, and Ronni Moffitt, his assistant at the Institute for Policy Studies, who were murdered six years ago last month by Chilean secret police.

Every anniversary since -- Sept. 21 -- a memorial service of speeches, songs and a rededication to human rights has been held at the traffic circle on Embassy Row in Washington, where a planted bomb exploded and killed the pair.

One brief service once a year isn't much to remind us that the goal that Letelier worked for -- the restoration of democracy and economic justice to his homeland -- remains unfulfilled. But it's something. If we listened only to other voices -- the Reagan administration, conservative economists -- we would conclude that Chile's government of brutal militarists is a model of political enlightenment that created, in Milton Friedman's words, "an economic miracle."

The violations of human rights and supression of dissent in Chile continue unabated. In August, eight critics of the Pinochet government junta were sentenced to expulsion. The government, mouthing anti-communist slogans used since the bloody coup of 1973 to justify mass killings and torture of political opponents, says the critics are dangerous leftists. They aren't at all. Two belong to the Chilean Human Rights Commission and another two are members of Justice and Peace, the organization whose leader, Adolpho Perez Esquivel of Argentina, won the 1980 Nobel Peace Prize.

The junta's sinking to still lower depths of shamelessness occurs when the Reagan administration is starry-eyed in its praise of the Pinochet government. Last July, Assistant Secretary of State Everett E. Briggs went to Santiago to praise the generals for their "devotion for the rights of man." He told them that their nine-year "program to return to a real and long-lasting democracy arouses the interest and solidarity of President Reagan's administration."

It isn't arousing the solidarity of many others. In Congress, 47 members, in a letter to the administration, have made it clear that they disapprove of its plans to restore the military aid that Congress cut off in 1976 because of state-sanctioned terrorism. The aid is conditioned on a requirement in the law for certification that Chile has made "significant progress" in human rights. Certification is also needed for the government's pursuit of Chilean officials who ordered the murders of Letelier and Moffitt.

The latter alone should be enough to block certification. Lawrence Barcella, the Justice Department prosecutor who oversees the Letelier-Moffitt investigation, said last week that he has yet to see "any cooperation at all" from the Pinochet government.

The question now is to what lengths the State Department will go to end-run the evidence that Chile is as undeserving of military aid today as it was in 1976 when the aid was withdrawn. Briggs said in July, "The present administration has tried to eliminate the remains of former problems and disagreements."

Tried, perhaps, but failed. The murder of two people, one a young American woman from New Jersey, is still not seen by officials like Barcella as a "former problem." It persists as a current horror.

If the Reagan State Department can't hide the human rights abuses, conservative economists are having less success in keeping up the cheers for the Chilean economy. Six months ago, unemployment was at 18 percent. Now it is at 23 percent, with unofficial estimates reaching 30 percent. Industrial production has declined 22 percent. Banks are failing and factories are closing.

The self-proclaimed miracle-worker, Milton Friedman, had long been counseling the junta. His free-market vision was to restore the economy so it could "be enjoyed by all." The poor were never helped. But now the wealthy are frightened that they are about to crash. Meanwhile, Friedman, leaving the ship with rodentine haste, said earlier this year that his free-market theories "will not last unless the military government is replaced by a civilian government dedicated to political liberty."

This liberty was the goal of Orlando Letelier. He was killed for working toward it. The unanswered question now is how many innocent victims the Pinochet regime will take down with itself as the pending collapse approaches.