How Loud is it in the Pilothouse?

The following noise level readings were taken while underway using an Ipod Touch 4G running Sound Level(TM)—a free app. I was standing in the middle of the pilothouse, facing forward. The Touch was held upright and was about 5'4" high . Hmm, looks like Nellie has a resonance problem at 800 rpm ;-)

RPM	Nellie D. (63)	Knock Off (66)
	db	db
600	65
800	79
1000	71	68
1200	71	72
1400	73	73
1600	75	72
1750		74
1800	77
2000	79	79
2200	83
2400	84