I don't have the ap30, but I have two linear pumps and they are not near as loud as I expected. One is the cheap ebay brand 50l and its not much louder than a whisper 100. I don't think it puts out a full 50l of air, but its still a lot. The other is a 50l Medo and its built twice as heavy and puts out more air, but is a bit louder.
Also take a look at the dolphin av-50. Its a diaphragm pump and I have heard nothing but good about it.
One thing I would note about blowers is they are high volume, but low pressure. At 20" of water depth the smaller one puts out 50l of air, but its 4x the initial price and uses 4x the electricity of a linear pump.