What podcasters can learn from filmmakers about audio
Podcasting is the new black! 2016 survey data from Edison Research show that 21% of Americans between the ages of 12 and 54 listened to at least one podcast episode per month. The podcast listener base has been growing consistently since 2013, and the 2016 figure is a 75% increase on 2013. The podcast audience in the United States in 2016 is 57 million people.
So it should be no surprise that there has been a proliferation of articles about how one might start podcasting. One of the common denominators with these articles is their suggestion of microphone choice. Almost invariably, these articles recommend a microphone with a USB connector so that one can plug it directly one’s laptop but this is not at all ideal.
Before we go any further, there are a couple of technical terms regarding microphone design that need explaining before we discuss the merits of various microphone designs for podcasting, and techniques of deploying microphones.
The first parameter is the polar pattern. The most common polar patterns are: omni-directional, cardioid and supercardioid. Photography probably provides the best analog for understanding these patterns. Think of omni-directional as the audio equivalent of a fisheye lens, cardioid as a normal lens (50 mm with a full frame camera), and supercardioid as a telephoto lens. So an omni-directional mic picks up sound almost all around it in 3D space — as the name implies. And a supercardioid mic pics up sound in a narrower blob-shaped space mainly in front of the mic.
The second parameter is the capsule-type. The capsule is what converts the vibrations of air into electrical signals. There are 3 main types of capsules: dynamic, condenser and ribbon.
Dynamic capsules are very robust and the least sensitive of the three capsule types. Consequently dynamic microphones are used in live performances where they are often dropped by roadies and performers. They are also used in noisy environments such as football stadiums and motor racing. Their lower sensitivity results in less background noise being captured. But there’s price to be paid for being less sensitive. Dynamic mics can make huge demands on the mic preamp in a recording device which results in the need to crank up the input level on the recording device, and that results in a hissy noise produced by the electronics of the device. Furthermore, most battery-operated portable devices do not have strong mic preamps.
The condenser capsule is probably the most popular of capsule type. Condensers have had a reputation of being delicate but modern manufacturing techniques have sorted that out. The big chunky mics that look like beer cans and which can be seen on many Youtube sets are large diaphragm condenser mics.
These large condenser mics probably made their way onto Youtube sets because they look imposing and make the pundit hosting the show look professional. Condenser capsules are also found in virtually all USB mics designed for the entry-level podcasting market. We’ll get back to these USB mics later when we combine capsule types with polar patterns.
Condenser mics are far more sensitive than dynamic ones but the former require 48 volts of electricity to operate. The 48 volts, known as phantom power, needs to be supplied by the recording device or mic preamp. Alternatively, some condenser mics will take a battery to supply phantom power within the mic itself.
Ribbon capsules are the most sensitive and fragile of the three capsule types. They are used almost exclusively to record vocals, particularly in jazz recordings. A ribbon mic picks up minute nuances of the human voice and imparts an alluring shimmer to the recording.
So with the technicalities done, it’s onto the relative merits of mic designs, and techniques for podcasters.
USB mics almost invariably use a condenser capsule with a cardioid polar pattern. This means that that such mics are fairly sensitive with a relatively wide coverage. These mics are targeted at newcomers to podcast production. A characteristic of podcasting newcomers is that they almost never work in an acoustically treated recording studio with heavy steel doors replete with rubber seals, and with similarly sealed double glazed windows to keep out noise from the external environment. These professional-type studios also have wider air-conditioning ducts to reduce air turbulence noise, and have walls that are treated to reduce resonance.
Most people starting out in podcasting often work from a room in their home where the acoustic environment is very different to that of a recording studio. So, while it’s extremely convenient to plug a USB mic into one’s PC or Mac, start up the audio software, and press the button with the red dot, the end result usually sounds very unlike podcasts from major players like Panopoly, Gimlet and NPR. That’s because these mics tend to pick up background noise.
As a result of their on-location work, digital and analog filmmakers have been trying for a very long time to prevent background noise from being recorded. Filmmakers use “shotgun” microphones that have condenser capsules with a supercardioid polar pattern. In Australia, they are fondly referred to as “shotties” by the industry. A shotgun mic’s narrower field of coverage reduces the amount of background noise being picked up. At the same time, its condenser capsule makes few demands of the mic preamp of the video camera. But the that’s not the whole secret of the filmmaker’s audio success.
In order to keep the shotgun mic out of the visual frame, filmmakers tend to position the shotgun a little above and in front of the subject’s head, inclined at a 45 degree angle towards the subject. Often, a sound recordist wields a boom pole to hold the mic in this position. And this miking technique allows filmmakers to minimize the recording of background noise coming from air conditioning ducts, from outside of closed windows, and from the outside of a closed door.
When podcasting, the shotgun mic can be held in this position with a full height mic stand with a boom arm.
To those starting out in podcasting, while it may cost you more money to get a shotgun mic, a digital audio interface with phantom power, a mic stand and a shock mount for the mic, you’ll almost certainly get much cleaner sound than with a USB microphone.
Although there is a lot more to podcasting than audio quality, high production values are extremely important in an increasingly crowded space.
Acknowledgements
Special thanks to filmmaker, David Muir, for his feedback and input to this article.
Key references
Shure: Microphone polar patterns/directionality
Getting better production audio
About the author
Kelvin Param is a partner at Profactual — a full-service podcasting consultancy. He is a co-creator of the research podcast from the University of Melbourne, Australia, Up Close. And was the show’s executive producer for eight years.
Follow:
Twitter: @kelvinparam
Web: https://www.kelvinparam.com and http://www.profactual.com
