Achieving Natural Sounds with Doppler + Air

By in Audio Post, Pro Mixing

It is great when we need to create wild sounds such as spaceships or monsters, but many times, the biggest challenge is to recreate ordinary sounds, the ones we are constantly hearing in real-life. The main problem is that all humans are experts in such sounds. Every person knows what sounds natural and what doesn’t sound natural. Thus, how can sound professionals create ordinary sounds which sound natural? Well, you need to use natural sounding tools… such as Doppler+Air.

Doppler + Air is a bundle with 2 plugins: Doppler, to create Doppler effects; and Air, to simulate distance by applying air absorption equalization.


When we released Sound Particles software, our users loved the Doppler sound. I recall David Farmer (Lord of the Rings/The Hobbit) telling me that it was the best sounding Doppler software he had ever used, to which I replied “Really!?”. I thought Doppler was one of those effects which were already perfectly handled by several plugins. However, most Doppler plugins are based on pitch-shifting, which needs to create in-existent audio blocks, resulting in lower quality sounds. In real-life, Doppler is mainly a variable delay, and with Sound Particles we implemented Doppler with a very high-quality variable delay, since we didn’t used the usual shortcuts to obtain better performance, which end-up having impact on audio quality.

Imagine that you want to record a specific Doppler kind of sound, for instance, a car passing by. During the recording, you choose the mic setup; its position; you give instructions to the driver about the desired velocity, etc. Doppler works in a similar way, recreating a real-life situation, with real-life parameters. Instead of a knob for pitch variation or smoothness, you will see velocity, mic distance, and similar things.

The screen is divided in 4 main areas. On the left, you specify the behavior of the moving sound: its velocity, direction, and acceleration (constant velocity, accelerating, breaking). Once the sound is moving, the next section defines the behavior of the air, including air absorption and distance EQ (yes, Doppler includes an Air plugin inside). The third section is about the microphone: how far is the mic, which mic setup to use, and its desired rotation. Different stereo pairs will result in completely different sounds. For instance, I love the ORTF pair, because the capsules are slightly apart, thus the resulting pitch variation on each channel is slightly different (like in real-life). The plugin also supports complex setups like 5.1, or 7.1.2, or up to 3rd order Ambisonics. The last section is mainly about time: when does the sound peak? It can either be specified in timecode (“I want the peak at 1:08:34:01”) or based on the signal (“3 seconds after detecting a signal”).

There might be some Doppler plugins with more “bells and whistles”, but if your major concern with a Doppler plugin is its sound quality, search no further.


As sound travels thru the air, the higher frequencies start to suffer attenuation, and as distance increases, more and more frequencies are attenuated. Air is a very special filter that truly replicates the behavior of air absorption, based on distance. You specify the distance, and the plugin applies the right amount of EQ to recreate that exact behavior (yes, we are science geeks).

Some may be thinking “Can’t we recreate the same exact behavior with a low-pass filter or any ordinary EQ?” Eventually, if you have the time and the skills, the same way a painter can almost recreate a real picture by using a brush, instead of using a photo camera. However, in this case, Air will give you much better and faster results.

The use of the plugin is straight forward: you use the big knob to specify the distance. If you want an even more accurate result, you can specify the temperature and/or humidity. Although everyone knows temperature values, humidity is slightly more complicated to know, so the plugin also includes some temperature/humidity presets (e.g. “London in the Spring”).

At some point, some users asked us if we could also add a global distance attenuation parameter, to allow them to automate distance to control both EQ and volume. As such, we added the distance attenuation parameter: zero if you want only EQ, any other value to add volume attenuation with distance.

Although Doppler seems to catch more attention than Air, many Hollywood professionals report that Air ends up being used much more, because they are constantly adding a sense of depth to most sounds on their mix.

Get 50% Off Doppler+Air

Explore the unique features of sound and movement and get the most natural sounding emulation for your work. Get it now for only $99 USD (reg. $199 USD).

Act now—offer valid between May 14 to June 14, 2019

Creator of Sound Particles software, used by all major Hollywood studios