"If you want quitet on a 738 get a seat toward the rear of the plane. Up front isnt as bad on the 738 as it doesnt make that whinny buzz sound like the A320 or 752 if you are in front of the engine."
I flew on the 738 last month and i was sitting in row 7- just in front of the left engine. I certainly DID hear the whiny buzz noise especially when take-off power was applied, and also during the climbout. During the cruise however the noise disappeared.