Effectively utilizing multiple microphones is potentially one of the most challenging tasks for an audio engineer. There is potential for comb filtering and undesirable localization effects if care is not taken to ensure proper phase coherence for the sources being recorded. In the case of the acoustic drum kit, it is common to use two microphone above the drum kit as overheads to capture the overall essence of the drum kit. In this case, it is desirable to maintain coherence for the kick and snare drums to ensure they are localized in the center of the stereo image and to avoid potential comb filtering effects. This can be a challenge for the audio engineer and current methods do not provide much feedback about the placement.
The goal of this project was to develop a real-time AU/VST plugin to provide additional feedback to the audio engineer about the phase coherence in regards to the kick and snare for their overhead microphone placements. To do so, the a plugin was developed using the C++ JUCE framework and a specific implementation of the Generalized Cross Correlation with Phase Transform (GCC-PHAT). The plugin can be run on stereo channel in a DAW containing the left and right overhead input signals. Then the snare and kick drums can be struck, and instantly feedback will be returned on the display showing the sample delay, path length difference, latency, and which of the two channels was delayed in relation to the other.
Check out the GitHub to check out the code for the JUCE project.
Latest working builds of the real-time phase analysis plugin.
These builds have been tested on Mac OS X 10.10.
For the most up to date code changes check the GitHub.
This project was one of seven other finalists in the Saul Walker Student Design Competition at the 143rd AES Convention.