Tool
The HaptiCoupler
The HaptiCoupler is a system designed to enable bidirectional tactile interaction with digital musical instruments. Effectively, it lets you both excite virtual instruments through the fingertips and also feel the vibrations of the virtual instrument at the same time. This is done with a single voice coil transducer (a loudspeaker without the speaker cone), acting as both a sensor and actuator simultaneously. This signle point of contact enables an intimate haptic coupling not normally possible with traditional digital musical isntrument designs that conform to a unidirectional tactile approach.
There are plenty of existing examples of digital musical instruments (DMIs) that using some form of audio input to excite a resonant synthesis – from simple Karplus-Strong string models to complex physical modelling with modal synthesis. The audio input to these "Hybrid Resonant Instruments" can take many forms, but often uses some form of surface pickup (e.g. a piezo disc) to transduce mechanical vibrations of a surface into the electrical domain. These vibration signals are what excites the resonant synthesis model - similar to how physical vibrations might excite a physically resonant surface such as a drum head.
This interaction paradigm provides scope for intimate control – subtle interactions can still create audio output and changes in the timbre of the excitation input will change the timbre of the synthesis. This is in contrast to other techniques such as sample-based synthesis, where an audio recording is triggered when the system detects a 'hit' on the audio input (possibly playing a different sample depending on the detected velocity/loudness).
While these techniques provide nuanced control of synthesis models, the tactile feedback from the interaction is limited to the static physicality of the interface. Unlike physical resonant systems – where the vibrations of the object can be felt and interacted with (e.g. damped by holding the surface) – hybrid resonant instruments normally use a damped surface/interface to avoid the physical system colouring the digitalc resonator's timbre. The vibrations, therefore, cannot be felt or interacted with in the same manner.
A simple solution would appear to be adding a
The HaptiCoupler system provides a means of interacting with hybrid resonant instruments while also feeling the vibrations of the synthesis output.
This kit is based around a Teensy 4.0 microcontroller in conjunction with a MAX98389 audio amplifier IC. The amplifier provides current feedback to the Teensy. The Teensy applies DSP to cancel the actuation signal from the sensed signal.
Audio rate signals are sent between the teensy and a host computer via USB (alongside serial and MIDI data for control).
This toolkit provides hardware and firmware for exploring [bidirectional haptic interaction](PROJECT PAGE LINK). The hardware and software is open source (LGPL 3).
More information on the kit and getting started with using it can be found on the corresponding GitHub repo Wiki.
If you would like to request to borrow a hardware kit for your own experimentation and exploration, please get in touch with Matthew Davison [LINK TO PERSONAL PAGE].
Alternatively, you are able to recreate the kit yourself using the provided source files on the GitHub repository.