Boston University Rocket Propulsion Group recently test fired their Iron Lotus rocket engine. Developing ~2500lbf (11.1kN) of thrust, the engine was tested for 1 and 3sec burn times.
As the name implies, the engine is a steel heat sink engine, not intended for long duration firing and primarily used for ignition testing, before the (flight) regen Lotus Dev 2 engine is tested.
That sound and echo are impressive!!