It's common question we receive; 'How much noise do your motors make?' or 'Can I record audio tracks with the motors running?'. It's honestly very difficult to specify a 'noise level' or answer with a yes or no because there are a multitude of factors involved..
Let's start with a little history, only since say 2010 has this question even started to crop up. Previously it was a forgone conclusion in filmmaking; motion control means no microphones.. In the Hollywood world even recording run and gun has very rarely been used, typically the entire sound bed including dialog is carefully crafted in a controlled environment. Meanwhile in the corporate, documentary and independent production world motion control generally wasn't an option, the budget just was not there for operators and expensive equipment. That all changed about the time Dynamic Perception was founded (2009) and we're proud that we played a big roll in that change.
Today moco rigs are affordable, they have found a place in a majority of filmmakers toolkit and have stated to play an important role in filmmakers storytelling. All that said, let's cut to the chase:
1. All motors make some noise.. there is unfortunately no such thing as a completely 'silent' motor.
There are very quiet motors most of which don't produce much torque or power because they lack gearing and there are motors that are muffled or shielded in various ways (adding bulk and weight). At the end of the day, all motors make some level of noise.
2. Motor speed plays the most significant role in noise
Simply put, the faster you run a motor the more noise it will make. If you can live with slower speeds you will reap the benefit of lower noise levels.
3. Harmonics also is a factor with noise
Although speed is the strongest influence, harmonics also come into play. Motors produce slight vibrations and although not visible they are audible.. Vibrations at different frequencies can interact with the internal components in the motor like gears and bearings or with external components they are attached to.. Certain frequencies can produce more noise than others. Many times slight adjustments to the motor speed can produce very different levels of noise even though the speed difference is slight.
4. Always use off camera microphones
Directional or lav microphones can help isolate unwanted noise coming from moco motors or any noise floor issues for that matter.
5. Defeat motor noise in post!
Adobe Audition has some very powerful tools to eliminate certain noise.. With stepper motors we are in luck, the noise profile is very easy to isolate and sponge out. They usually show up as distinct 'lines' in the Spectral Frequency Display. This makes them very easy to isolate and eliminate with noise envelopes and reduction filters.