Things that go bump on a plane are enough to make anyone feel a bit anxious about flying. But before you start rushing the emergency exits and reaching for your life vest, you’ll be relieved to know that many of the noises heard on an airplane are actually very common and no cause for concern.

OnTheAir recently compiled a list of five common sounds you might hear when flying and what they mean:

1) A “poof” of air at the gate
Before the plane takes off, a loud ‘poof’ can often be heard. This just means the ventilation has switched from an outside system to one inside the aircraft.

2) A ‘bark’ as the plane taxis
When the plane travels down the runway, either departing or arriving, it will make a strange barking sound. No, it’s not the sound of dogs coming from the cargo – it’s the hydraulics, or more specifically, a device called a Power Transfer Unit (PTU) that balances the hydraulics. Totally normal.

3) ‘Whir’ of the wings
Once your plane takes off and it’s safely in the air, you’ll hear a whirring sound. This occurs when the flaps first increase the wingspan and then retract to help give lift.

4) ‘Bang’ from the belly
In everyday circumstances, a loud bang is often a sign of something gone wrong. Not so much on a plane, it seems. This particular loud bang occurs when the landing gear drops at around 2,000 feet during the plane’s descent.

5) ‘Screech’ of the brakes
When the brakes in your car screech, it usually means it’s time for a tune up. But when a plane’s brakes screech after landing, it just means that the pilot needs to maintain a certain speed to reach the runway, generally around 100-150 miles per hour. A little screeching is normal, especially considering the plane weighs 400,000 pounds.