The Hunt for Red October (Jack Ryan, #3)

by Tom Clancy

Ron”—he poked the sonarman in the shoulder—“that’s all right. Damned well done!” “Thanks, Skipper.” Jones’ smile stretched from ear to ear. “Pat, please call Lieutenant Butler to the attack center.” Mannion went to the phones to call the boat’s chief engineer. “Any idea what it is, Jonesy?” Mancuso turned back. The sonarman shook his head. “It isn’t screw sounds. I’ve never heard anything like it.” He ran the tape back and played it again. Two minutes later, Lieutenant Earl Butler came into the attack center. “You rang, Skipper?” “Listen to this, Earl.” Mancuso rewound the tape and played it a third time. Butler was a graduate of the University of Texas and every school the navy had for submarines and their engine systems. “What’s that supposed to be?” “Jonesy says it’s a Russian sub. I think he’s right.” “Tell me about the tape,” Butler said to Jones. “Sir, it’s speeded up ten times, and I washed it through the BC-10 five times. At normal speed it doesn’t sound like much of anything.” With uncharacteristic modesty, Jones did not point out that it had sounded like something to him. “Some sort of harmonic? I mean, if it was a propeller, it’d have to be a hundred feet across, and we’d be hearing one blade at a time. The regular interval suggests some sort of harmonic.” Butler’s face screwed up. “But a harmonic what?”