DIY Interference Tubes Pt. 2
Here's part 2 of my exploration into interference tubes. WARNING, it's a very image intensive post, but what isn't these days...
Here's part 2 of my exploration into interference tubes. WARNING, it's a very image intensive post, but what isn't these days...
A standard shotgun microphone is essentially just a microphone capsule and an interference tube. The capsules are simple enough, it's these interference tubes that are (apparently) complicated. An interference tube is a tube with slots cut into it to cancel out any sound coming from off axis. Any sound coming from on axis (straight down the shotgun tube) will hit the microphone without any interference ie the loudest sound. Any sound coming from off-axis will encounter the slots and bounce around in the tube until they are cancelled out with each other or attenuated down to nothing (inverse-square law). The pattern of slots on the tube can vary, depending on the amount of rejection wanted, and the effects on different frequencies. Also, generally speaking, the longer the interference tube, the better the off-axis rejection (more directionality). So I decided, why not make my own interference tube and save a bunch of money? I did a whole lot of research on the web, and was surprised to that no one had tried this. At least, no one had documented trying this, maybe it was so complicated that they failed and didn't bother posting their results online. Well I hope to change all that.