On the way to manila from Guam, i heard very noisy and annoing engine sound and it lasted about 45 minuets which was not normal. I asked a flight attendant why this plane makes this kind of noise because it didn’t seem to be safe, and she replied that it is normal to them. To me they are kind of insensitive to safety and it shouldn’t be normal at all. It sounds like high frequency rattling during take off and climb to altitude. Please inspect for passenger safety and confidence.