After twidling their thumbs for a day, U.S. stock investors today apparently turned thumbs down on President Carter's new energy policy designed to make the nation less dependent on foreign oil.

Trading volume picked up sharply on the New York Stock Exchange today, but prices fell. The Dow Jones Industrial Average, the most-closely-watched barometer of stock prices, fell 6.40 to 828.50.

The New York Stock Exchange index of the average price of a common stock fell 55 cents to 57.88.

"It was a delayed appraisal of President Carter's energy message," said Newton D. Zinder, market analyst for E.F. Hutton & Co.

Monday, the day after Carter's first energy address, stock prices rose slightly. But most investors seemed to adopt a wait-and-see attitude as trading volume was the lowest in nearly six weeks, with only 26.6 million shares changing hands.

Trading has been thin in most other world financial markets as well - from foreign exchange to gold trading bonds and other money markets - but prices declined, the dollar weakened and gold which usually moves in the opposite direction from the dollar, rose.

It was a repeat performance in the rest of the world today, except on Wall Street. The dollar continued to weaken, interest rates rose and bond prices fell, and gold reached new highs.

Volume on the NYSE increased to 34.5 million shares.

Analysts said investors were as shaken by the foreign reaction to Carter's speech as they were by their own appraisal. Saudi Arabia has said that if the dollar should continue to decline, the U.S. currency would be replaced as the sole currency in which oil is bought and sold worldwide. Already, Iran has began to accept payments for its oil in marks, yen and French francs.

International Business Machines Corp. was the most active issue on the NYSE today, with 555,200 shares changing hands. IBM closed down $1.125 a share at $69.375.

RCA Corp., which reported late Monday that its second quarter operating earnings were off 20 percent, was also among the most active, dropping $1 a share to $23.375.

In all, 1,059 issues fell in price today, while only 414 rose. Monday, 829 issues advanced in price, while 593 declined.

On the American Stock Exchange, the index of common stocks was down 1.72 to 195.46. More than 400 issues declined, while 182 gained in price.

Composite volume of NYSE issues traded on all exchanges and over the counter rose to 39.4 million from a slim 30 million the previous day. OTC prices, as measured by the NASDAQ index, declined 1.03 to 137.86 as volume rose to 17.5 million shares from 14 million. CAPTION: Graph, The Market July 17, The Washington Post