Shotgun microphones are used to capture sound at a distance. They are often used for sporting events, news reporting, drama and documentary filming as well as live broadcasting. In many situations, shotgun microphones are an important part of a sound engineer’s gear kit.
A highly-directional microphone, also referred to as shotgun microphone, is often mounted on a boom pole and pointed directly at the sound source, for instance an actor in a film. Other, perhaps less-known uses of shotgun mics is in the surveillance and security industry as well as music production for stage miking of, for instance, opera soloists.
In some audio situations, it is a struggle to isolate sound sources enough from the surrounding noise. In the broadcast and film sector, preserving the intelligibility of the talent and separating their dialog from disturbing elements like passing traffic or other environmental noise is critical. In these situations, either a very narrow directional microphone characteristic or a bodyworn microphone is necessary. To further sharpen the directional characteristics of a directional microphone, an acoustic interference tube can be added.
Using interference tube technology
An interference tube is an acoustically semi-transparent tube placed in front of a microphone capsule to achieve higher directivity. The general idea is that the on-axis sound passes directly through the mic to the membrane. However, the sound arriving from the side of the mic is somewhat dampened due to different path lengths inside the tube. The interference tube is normally the most directive at higher frequencies.
Extensive research and development have been undertaken by DPA to optimize the sound coming from the sides and back of our shotgun microphones. One of the key accomplishments is that we have minimized the often non-linear response of our shotgun mics due to their side lobes.
DPA’s high-quality condenser capsule uses a high voltage pre-polarized back plate. This endows the shotgun with high output as well as wide dynamics, extremely low noise and distortion specifications. The sound coming from the sides and back of many other shotgun mics often seem unnatural. Fortunately, DPA has managed to make these additions sound natural as well – just damped.