Shotgun microphones are used to capture sound at a distance. Often used for sporting events, news reporting, drama and documentary filming as well as live broadcasting, 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 to directly “hit” 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, it is about preserving the intelligibility of reporters or actors and separating their dialog from disturbing elements like passing traffic or other environmental noise. In these situations, either a very narrow directional microphone characteristic or a bodyworn microphone is necessary and to further sharpen the directional characteristics of a directional microphone, an acoustic interference tube can be added.
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. The condenser capsule uses a high voltage pre-polarized back plate, endowing 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 a shotgun often sounds unnatural but DPA has managed to make these additions to sound natural as well – just damped.