First introduced in 1970 as a full-size car, the Monte Carlo had been downsized to a mid-size by the time the last rear drive model appeared in 1988.

Talking to engineers and mid-level executives, Mr. Toyoda said the rapid expansion exceeded the company's ability to assure the quality and reliability of each model.

The computer model finds that mid-frequency sonar is mostly filtered out for the whales, while the higher frequencies the animals use for hunting appear to be unimpeded by sonar.