As Bud nodded, Tom went on, “So we simply
DETECTION TEST 117
step up the volume till the sub’s own noise gets drowned out or ‘wasted’ in all the racket.”
This could be done, he concluded, with fairly simple amplifying equipment.
Bud, Hank, and Arv were jubilant at the idea.
“Nice going,” Bud said. “How soon can we give it a try?”
“Soon as I can rig up the amplifier,” Tom promised.
In less than two hours they were ready to submerge again. Zimby Cox joined the crew. Bud suggested taking along hydrolungs in case of any need for tinkering with the transducers or amplifying equipment.
This time, the jetmarine scored perfectly on the test, successfully eluding all the Sea Hound’s efforts to detect it. Tom returned happily to base, feeling that the antidetection problem was now solved. The jetmarine, however, failed to appear.
“That’s funny. The test was over at four-fifteen,” Tom murmured.
“Maybe Bud surfaced out at sea somewhere,” Arv Hanson suggested.
Repeated radio calls brought no response. Tom, now seriously worried, took the seacopter down again for another search, hoping that Bud would have switched off the antidetection gear by this time. But neither sonarscope nor listening devices revealed the slightest clue.
118 THE ELECTRONIC HYDROLUNG
Tom, Hank, and Arv exchanged fearful glances. Had the jetmarine foundered on the ocean bottom-perhaps fouled somehow by Tom’s new invention? Or had Bud and his crew fallen victim to the enemy?
CHAPTER XIII
ENEMY FROGMEN
AT THE end of the test period, Bud had prepared to bring the jetmarine to the surface. But just as he was about to blow the ballast tanks, Mel Flagler sang out a warning from the sonarscope.