# How much noise would the BFR make at launch?

In addition to multi-planetary travel, SpaceX has plans to use the BFR for intercontinental travel. However, would the sound generated by the BFR's launch disrupt local communities and therefore make it unfeasible to set up launchpads across the Earth.

Specifically, how much sound would the two sea level Raptor engines (each with a an approximate thrust of 1,993 kN or about 448,000 lbf) make, and as the sound travels (and loses strength due to the inverse square law) affect nearby communities?

• The '2 sea level Raptor' line indicates you assume they'll only use the BFS (the second stage) for intercontinental travel. But the presentations indicate they plan to use the full stack. Nov 18, 2018 at 12:36
• The BF rocket would make a BF noise!
– uhoh
Nov 20, 2018 at 2:00
• Step 1. Make rocket noises with your mouth. Step 2. It's a lot louder than that. Feb 1, 2019 at 4:01
• The version originally announced had 3 sea-level engines for redundancy (the graphics were already obsolete at the time of the presentation). For the version they're working on now, all 7 of the engines are identical and designed to operate from sea level to orbit (to eventually be replaced with more optimized sea level and vacuum versions like in the original plan). In any case, operating as a single-stage hopper, Starship would need all 7 engines at liftoff. (The test hopper they're building now only gets away with 3 because it has smaller tanks and carries no payload.) Feb 1, 2019 at 23:45

The noise will be comparable to a Saturn V launch, on the exceeding side.

The dimensions of the BFR are roughly those of the Saturn V. The BFR thrust is about 1.5 times that of the 5 first stage F-1 engines. Running engines are by far the largest contributor to launch noise (followed by astronaut banter). I hesitate to put a number in decibels on it, since that depends on a lot of factors like distance. Would it really help? Can you imagine how loud 135 dB are? 200? I can't imagine how loud a jet engine is. But I will say Disaster Area, a plutonium rock band from the Gagrakacka Mind Zones, is louder. Google it :-)

• The engines don't produce coherent sound, their emissions cancel as well as reinforce each other. Adding 5 engines is an increase of 7 dB, 28 engines gives you 14.5 dB. Assuming the noise on a per-engine basis is proportional to thrust (it's not, really, but it's good enough for this rough calculation), a F-1 is 9.5 dB louder than a Raptor, and 5 F-1s will be 2 dB louder than 28 Raptors. The differences in clustering, plume geometry, exhaust velocity and composition, etc will likely make this estimate very inaccurate. Feb 13, 2021 at 20:31
• Additionally, the Bel (and by extension, a deciBel) is not a linear unit. Feb 13, 2021 at 20:37