Other than it being ~500'AGL instead of ~2,000', that does sound like the "low noise" take-off the B737, & B727 I flew in (as passenger) out of John Wayne Int'l (Orange County, CA) in 1985 & 86.
It has the same engines as the E3's that fly from the same place which do departures without managing to make onlookers go wobbly. It and the E3 aren't exactly noisy anyway..
As Lord Flasheart says, it may have been a practice something or other. I was merely commenting on the odd departure.