Low pass vs band pass filter I've been reading some EEG papers where the authors use a bandpass filter at, say, 1Hz and 30Hz. I've also seen some accelerometer papers where they bandpass at 0.5Hz and 10Hz

What is the difference between a bandpass (1Hz, 30Hz) and just a regular low pass filter at 30Hz?

It seems like they're trying to remove really low frequencies, but does it really make that much of a difference? Is there a particular reason why this is done?
A bandpass filter allows signals between two specific frequencies to pass, but that discriminates against signals at certain frequencies. 

A lopass filter is a filter that passes signals with a frequency lower than a certain cutoff frequency and minimizes signals with frequencies higher than the cutoff.

There's a slight distinction. What's useful depends on the situation.