I am collaborating with Chad Loughrige (head of Music Technology at Capital University) on a series of projects. These cross the boundary between hardware and software. They are presented here as “one-offs” in the sense that they will not be offered with complete details.
Binaural Microphone
These have been around for quite a few years and use a physical model of human ears to make stereo recordings which are startlingly realistic (at least in spatial orientation) when played back through headphones. There are commercially available sets.
This seemed like a good project to make since the hardware is simple and inexpensive and a good application of 3D printing for the ears. The ears were created by editing an available 3D model of the human head and then printed in TPU filament, which made them somewhat flexible. A wooden frame was fabricated to approximate the spacing on a real head and to hold the other components. Since our set was intended for studio use, it was wired with two XLR jacks using the voltage divider circuitry detailed here to bring the 48 volt phantom power supplied to the unit down to about 7.5 volts. A matched set of Primo EM172 capsules were used. The frame has a 1/4 inch threaded insert in the center for mounting to a stand.
The microphone has performed well in early testing and will be easily modifiable by printing different versions of the ears (which are attached to the frame with VHB tape).
AR Headphone Module
This is an add on module for a set of headphones that creates a true spatial sound field. The module attaches to the top of the headphones, tracks the listener’s orientation (currently just using compass readings) and sends that via bluetooth to an app (created in Unity) that adjusts the spatial sound field to the orientation of the listener’s head. In other words, as you turn your head the sounds stay where they are as if you were listening to live musicians.
The location services are provided by a 9-DOF IMU sold by Adafruit. For initial testing the output was sent to an Arduino and then over a simple serial bluetooth link. The final hardware consists of the IMU, a BLE bluetooth module–also from Adafruit, a battery that can be recharged from the bluetooth module. and a power switch in a 3D printed case.
The software side is a very simple application in Unity at present. The camera is placed among objects with sound files assigned to them. Compass readings are fed in over the bluetooth connection and the Unity camera rotates accordingly. Obviously there is great potential for developing a more sophisticated application. Unity makes it pretty easy to export the application to a variety of platforms for playback and field use.
