That noise! A guide to normal sounds on a flight
Thunks, whirs, chimes and the famous "barking dog" — what you're hearing, from gate to gate.
In this article · 5 sections
Airplanes are full of motors, pumps and moving parts — and each one makes a noise. Here's what's normal, roughly in the order you'll hear them. (Exact sounds vary by aircraft type.)
At the gate and while taxiing
- A low hum or whine before the engines start — the auxiliary power unit (APU), a small engine in the tail that provides electricity and air conditioning on the ground.
- A brief silence and the lights flickering — power switching from the APU or ground power to the engines. Completely normal.
- A buzzing or "barking" sound on some Airbus jets — often a hydraulic power transfer unit balancing pressure between hydraulic systems while one engine is running. It sounds odd; it's normal.
Takeoff and climb
- The roar of takeoff power, followed by a noticeable reduction a minute or two later. Pilots often reduce thrust once safely airborne, to a climb setting — engines aren't failing, they're being managed (and kept quieter for people on the ground).
- A thunk and a rumble shortly after liftoff — the landing gear folding up into its bays and the doors closing.
- A whirring sound — flaps and slats (the extensions on the wings that help the airplane fly slowly) retracting in stages.
- A "ding" — the cabin chime. Pilots and flight attendants use it to communicate; one or two chimes after takeoff often means the crew can get up and start service.
Cruise
- A steady whoosh — air flowing past the fuselage. Changes in pitch usually mean small speed or altitude changes.
- The seat belt sign turning on — passengers must be belted whenever it's lit, and it's often turned on as a precaution before expected bumps.2
Descent and landing
- Engines getting quieter at the start of descent — airplanes often descend with the engines near idle, almost like gliding downhill.
- Whirring again — flaps coming out in stages for the approach.1
- A rumbling, then a thud — the landing gear coming down and locking, sometimes several minutes before landing.
- A loud roar right after touchdown — reverse thrust helping to slow down. Along with the spoilers popping up on the wings, it's how the airplane stops smoothly.
Rule of thumb: if the crew are calm and continuing their normal routine, the noise you heard was routine too. Ask a flight attendant — they're happy to explain.
Keep reading
- Why does it feel like the plane is dropping after takeoff?
- Is this normal? The sound-by-sound library
- Save the in-flight pack before you fly: it works offline. For a calm week of preparation, see 7 days to your flight.
Quick answers
What is the barking dog sound on a plane?
On some Airbus jets it's often the power transfer unit, a hydraulic device balancing pressure between systems while one engine runs. It sounds odd and is normal.
What is the loud thunk after takeoff?
Usually the landing gear folding up into its bays and the doors closing.
Why do the engines get quieter after takeoff?
Pilots reduce from takeoff power to climb power once safely airborne. The airplane keeps climbing.
What is the roar right after landing?
Usually reverse thrust helping to slow the airplane, along with spoilers popping up on the wings.