4-31. 4-32. 4-33. When positive gradient conditions exist in the ocean, layer depth is defined as the depth of which of the following temperatures? 1. Minimum temperature 2. Maximum temperature 3. Optimum temperature 4. Relative temperature Which of the following cruising maneuvers by a submarine should prove most effective in causing a surface vessel to lose contact with the 1. 2. 3. 4. submarine? Cruising in a uniform temperature area Cruising above layer depth Cruising below a thermocline Cruising in an isothermal layer A car is waiting at a crossing for a train to go by. The driver of the car honks the horn as the train approaches. After the train passes the crossing,   the engineer on the train blows the whistle. How will the sound of the car horn heard by the train engineer compare to the sound of the whistle heard by the car 1. 2. 3. 4. driver? The horn will sound lower than it actually is, and the whistle will sound higher than it actually is The horn will sound lower than it actually is, and the whistle will sound lower than it actually is The horn will sound higher than it actually is, and the whistle will sound higher than it actually is The horn will sound higher than it actually is, and the whistle will sound lower than it actually is 4-34. As a sound emitter moves away from a receiver, which of the following apparent changes will occur? 1. 2. 3. 4. Only frequency will increase Only wavelength will increase Wavelength and frequency will increase Wavelength will decrease 4-35. Which of the following sounds are rarely heard by the sonar operator? 1. Pings 2. Target echoes only 3. Reverberations only 4. Reverberations and target echoes IN ANSWERING QUESTIONS 4-36 THROUGH 4-39, SELECT FORM COLUMN B THE RELATIVE PITCH OF THE REFLECTED SOUND THAT IS MOST DESCRIPTIVE OF EACH OF THE MOTION CONDITIONS LISTED IN COLUMN A. NOT ALL RESPONSES IN COLUMN B ARE USED. 4-36. 4-37. 4-38. 4-39. A. RELATIVE MOTIONS B. RELATIVE PITCH Sonar stationary, all signals received classed as reverberation echoes Sonar and target moving in opposite directions, and separating Sonar and target moving toward each other Sonar and target moving abreast and the same direction 1. Higher 2. Lower 3. Same 4. Undulating in 26