Live From PyeongChang: Extreme Cold Affects Mic Operations
Vendors offer suggestions for adapting to the weather
The Winter Olympics is putting cold-weather sports on the front burner. The temperatures in PyeongChang — at a rehearsal for the Opening Ceremony, the temperature was 6 degrees F with a wind chill of -7 degrees, so cold that audiences walked out in the middle of the rehearsal, according to USA Today — reaching record lows for the Games, are putting the performance of the most fundamental broadcast-audio element, the microphone, in the spotlight.
Audio-Technica, whose AT4050ST and BP4025 stereo mics are used to capture venue ambience in various venues, cautions via its blog that the most prevalent problem with using microphones in an extremely cold environment is that a stiff diaphragm can become noisy.
“Freezing the mic will not hurt it. However, with freezing, you automatically create humidity. There is no way around this,” the commentary warns. “If you use the mic in freezing temperatures, you should expect it to be noisier and have frequency-response changes (due to stiffness of the diaphragm), and for there to be added noise (due to moisture, which [affects] element capacitance).”
According to Michael Johns, product manager, wireless systems, Shure, wireless microphone systems like Shure’s Axient Digital, 10 channels of which are deployed on the ski runs in PyeongChang, can be directly affected by extremely low temperatures. For starters, the LCD displays that indicate channels and battery status can become less responsive and, at some point, blank out completely. In addition, rechargeable batteries are specified to work only within certain temperature ranges.
“If the temperatures get low enough,” he explains, “it can affect the performance of the battery, interfering with delivery of current to the microphone or bodypack, and also affect the ability of the battery be recharged.”
(In fact, many battery warranties will not cover recharging applications below 32 degrees F. See this forum for a lengthy and detailed explanation of ion transfer rates and related issues.)
Johns also points to wind as anathema for wireless microphones, though not for the usual reasons having to do with inducing noise in the capsule. Rather, he says, the kinds of extreme winds found in very high altitudes, like winter-sports sites, can play havoc with the decidedly non-aerodynamic shapes of typical wireless systems’ antennas: “Antennas are often shaped like paddles and can act like sails in the wind.”
The solution is to be aware of wind speed and direction and to gaffer antenna stands when necessary.
Most local weather forecasts cover wind speed and direction, as well as the potential for gusts. If the event site is near an airport, very specific, on-demand information can be obtained from the local Automatic Terminal Information Service (ATIS), which broadcasts that information on a loop on a separate frequency from approach and tower frequencies. Local ATIS frequencies can be obtained through this link. (The writer knew his flight training would come in handy at some point.)
Johns adds that Axient Digital’s design enables key elements, such as bodypack clips, to be accessed with gloved hands and battery compartments to be accessed with one ungloved hand. In addition, the Axient series is currently undergoing Ingress Protection ratings testing, which will provide users with standards-based levels of sealing effectiveness of electrical enclosures against intrusion from moisture.
The Winter Olympics will go on through Sunday, but, because Punxsutawney Phil saw his shadow several weeks ago, broadcasters can likely expect cold-weather operations to continue for a while.