Recording engine sound: microphones, wind protection and levels

The aircraft sits at the threshold, the picture is sharp, the pan is set – and then an A330 goes to takeoff power and your clip falls apart into a rasping noise. When recording engine sound, most mistakes happen not at the camera but at the microphone, in the wind and with a wrongly set level. This guide shows you which microphones are suited to aircraft, how to deal with wind at the open fence, why you should record too quiet rather than too loud and why the sound of an aircraft always arrives late.

Why good sound is so hard in aircraft videos

Hardly any video subject has such extreme dynamics as an airport. Between birdsong at the fence and a long-haul jet at takeoff power lies an enormous difference in loudness. Engines can reach over 140 decibels at takeoff, and even a few hundred meters away the signal remains enormously loud for a microphone. At the same time you want to capture the quiet moments before: the whistle while taxiing, the spool-up, the moment just before brake release.

Then there is the environment: airport grounds are open, flat and windy, and you often stand on hills, embankments or at fences with no cover at all. And unlike a passing train, a departing aircraft is audible for minutes, moves away in three dimensions and constantly changes its sound as it does.

The good news: three adjustments get this under control – microphone choice, wind protection and level. How sound fits into the overall package of camera, tripod and composition is described in the basics guide Shooting plane spotting videos.

What you actually record at an airport

Before you choose a microphone, it is worth looking at the sound sources. An aircraft sounds completely different depending on the phase of flight, and each phase places different demands.

• Jet noise: Most of the engine noise is generated behind the engine, where the hot exhaust jet meets the still ambient air and becomes turbulent. This is the deep, broad roar of the takeoff roll, heard most strongly at an angle behind the aircraft.
• Fan noise: Modern turbofan engines have large fans. When their blade tips reach supersonic speed at high power, the typical growling “buzzsaw” noise results, which many spotters love especially on big twinjets.
• Airflow noise: On landings with flaps and landing gear extended, the airflow around the airframe becomes clearly audible. Add touchdown, reverse thrust and braking.
• System noise: On the ground you hear auxiliary power units, hydraulics and pumps. The best-known example is the “barking” noise of the power transfer unit on the Airbus A320 family, which occurs mainly during engine start or shutdown with only one engine running.

For each of these sources there is a better position. If you want the takeoff roll with the full roar, you stand to the side behind the departure point. If you collect system noises, you need to be close to the apron or taxiway – on observation decks, for example. The basic question of which phase of flight you want to film is settled by the comparison Spotting landings or takeoffs.

Which microphones suit aircraft sound

Shotgun

A shotgun microphone picks up preferentially from the front and attenuates sound from the sides and behind. For aircraft that is ideal when you want to isolate a specific event: the touchdown of the main gear, an engine spooling up at the holding point or a single aircraft at a busy spotters’ hill with conversations next to you. The catch: a shotgun has to follow the aircraft. Mounted on the camera it follows automatically; on a tripod of its own you quickly lose the subject off-axis.

Stereo microphone (XY, ORTF, MS)

A jet moving from left to right through the soundstage, taking its Doppler effect with it, is the classic of spotter videos. For that you need stereo. XY arrangements are compact and sound clean even in mono, ORTF feels more spacious, and mid-side (MS) microphones let you still change the stereo width in the edit. Many handheld recorders already have an XY capsule built in.

Camera and smartphone microphones

Built-in microphones are the stopgap: they pick up handling, zoom and autofocus noise, have hardly any wind protection and often adjust automatically. As a reference track for synchronization they are still worth their weight in gold. If you film with your phone, you will find fitting tips in the guide Shooting aircraft videos with your smartphone; a small clip-on microphone with a furry windscreen often brings the biggest jump there.

Microphone type	Strength	Weakness	Typical use at the airport
Shotgun	isolates one event, attenuates surroundings	has to follow the aircraft, sensitive to wind	touchdown, spool-up at the holding point, loud spotters’ hills
Stereo XY	compact, mono-compatible	rather narrow stereo image	flybys, takeoff roll from the side
Stereo ORTF	wide, spatial soundstage	larger, more delicate	atmosphere on the deck and apron
Mid-side (MS)	stereo width adjustable afterward	needs decoding in the edit	flexible all-round recordings
Camera microphone	always with you	automatic gain, wind, housing noise	sync reference, emergency

Wind at the fence: the enemy you can’t repair

Wind creates pressure fluctuations at the microphone capsule that are recorded as a deep rumble and thumping. The tricky part: this rumble sits exactly in the frequency range where the engine drone has its foundation. A filter that removes one takes the punch away from the other.

Here is how to build your protection in stages:

• Foam: helps indoors against drafts, practically ineffective at an open airport.
• Furry windscreen: the minimum equipment for any outdoor recording. It swallows a touch of highs but saves the recording.
• Basket with fur cover: for exposed spots on hills and embankments, where it almost always blows.
• High-pass filter (low-cut): as a supplement, not a replacement. Set it rather low so that the deep drone of the takeoff roll is preserved.
• Find cover: A car, a hedge or your own body between the wind and the microphone often does more than any accessory.

As a reminder: landings and takeoffs are made into the wind. If you plan around the runway direction in use – as explained in the guide Understanding the runway direction in use at an airport – you also know from which direction the wind will hit your microphone. A forecast for it is provided by Windy and other weather maps. In storms and crosswinds this applies doubly; the article Filming crosswind landings and storms fits here.

Setting levels: the takeoff-power trap

The most common mistake in aircraft videos is not a piece of equipment but a knob. You set the level while the aircraft is still taxiing – everything seems quiet, so you turn it up. Then the pilots push the thrust levers forward, and the peaks are cut off. This clipping is permanent: whatever was above digital full scale is gone.

Here is how to proceed:

1. Automatic gain off. Automatic level control pulls down during the takeoff roll and then back up afterward. You hear this pumping immediately.
2. Start deliberately low. Better much too quiet than just right. Digital audio can be raised cleanly later.
3. Orient on the loudest moment. As a rule of thumb, aim for a peak around –12 dBFS at the loudest event, so there is still headroom for reverse thrust or a low flyover.
4. Use a reference. The first takeoff of a session serves for setting levels. After that you correct for the interesting aircraft.
5. Let a safety track run. Many recorders write a second, much lower-level track in parallel. It is the cheapest insurance against a ruined recording.

Also consider distance: in the free field, the level of a point source loses around 6 decibels per doubling of distance. A jet that is 300 meters away at liftoff and later flies almost directly over you at 150 meters altitude can therefore become noticeably louder than the first impression suggests.

32-bit float: level worries almost abolished

Some recorders record in 32-bit float format and work with two analog-to-digital converters for quiet and loud signals. Manufacturers such as Zoom advertise this by saying you no longer have to set the input level at all and clipping does not occur in the file – you set the loudness only in the edit. For the enormous dynamics at an airport, that is a real gain. Two limits remain: a microphone that is itself overloaded still distorts, and even the best file doesn’t help against wind.

Sound is slow: syncing audio and picture

At the airport an effect occurs that railfans hardly know: you see the aircraft immediately but hear it only later. Sound travels through air at around 343 meters per second (at 20 °C, a bit slower in the cold). An aircraft a kilometer away is heard with a delay of almost three seconds. At 25 frames per second, that is over 70 frames of offset – clearly visible when the landing gear touches down and the squeal only comes afterward.

Whether you correct it is a matter of style. The offset is honest; many viewers know it from thunderstorms. But if you want to show touchdown or reverse thrust precisely, you shift the audio track forward in the edit by the travel time. For flyovers the distance changes constantly, so there is no perfect correction – orient yourself on the most important moment.

For the actual synchronization of external recorder and camera, the proven rule applies: always let the camera audio run too and set a clear signal at the start – a sharp clap close to both devices. Many editing programs then align the tracks automatically via the waveform. What this looks like in practice is shown in the guide Video editing for spotters.

From the spot to the edit: the workflow

In post-processing, the rule is: as little as possible. Remove residual rumble with a gentle high-pass, match volumes between clips and add a light limiter against peaks at the very end. If you lay music underneath, never let the engine sound drown in it and clear the rights beforehand – more on this in the article Music and rights in spotting videos. Recorded radio traffic also has rules of its own, which the post Publishing aviation radio in videos explains.

Hearing, law and consideration

Anyone who loves engine sound exposes themselves to a lot of noise. The reflex to turn the headphones up to drown out the noise outside is the wrong one. Listen only to set levels and check, and protect your ears separately otherwise. What aircraft noise does to hearing is covered in the article Aircraft noise and hearing. At extreme places like Maho Beach on Sint Maarten, where departing jets blow their exhaust over the beach, it is moreover not just about loudness but about real risk of injury – no sound is worth standing in the jet blast.

Legally the same applies as for photography: stay on public areas, respect the operator’s house rules on decks and parking structures, and leave ladders or large setups only where they are allowed (more under Ladders, steps and tripods at the airport fence). An overview is given by Is plane spotting allowed?. With sound, one point is added: shotgun microphones pick up conversations of bystanders surprisingly clearly. Scenes with clearly intelligible conversations of others should be removed or faded before you publish.

Common mistakes with aircraft sound

• Setting levels on the taxi phase. The classic – and the sure way to clipping during the takeoff roll.
• Working without headphones. Level meters don’t show wind rumble, cable crackle or rustling on the fur.
• Microphone fixed to the camera at long focal lengths. Zoom and stabilizer noise end up on the track. A shock mount or a recorder on its own tripod helps.
• Setting the high-pass too high. Then the wind is gone, but so is the punch of the engine.
• Only one recording of rare visitors. When an Antonov An-124 or a Boeing 747-8 is expected, ideally two devices run.

Which camera and video settings go with good sound is covered in Video settings for aircraft footage, and a shopping list to get started in Video equipment for beginner spotters.

Conclusion

A takeoff is first of all an acoustic experience – the picture shows what happens, the sound makes it felt. If you want to record engine sound, you don’t need a huge budget but the right priorities: a microphone that can handle high levels, a real furry windscreen and plenty of level headroom, optionally via 32-bit float. Add to that the knowledge that sound takes time and that audio and picture drift apart for distant aircraft. Try it out at your home spot, such as the Affenfelsen in Hamburg or the Butzenbüel in Zurich, and check the recording briefly after every takeoff – after a few sessions the routine sticks.