One goal driving the research conducted in the lab is to predict and manipulate compensation to different forms of altered auditory feedback of speech. Acoustic parameters that have been manipulated so far include speech intensity, fundamental frequency and voice-onset time. These manipulations have been implemented in both behavioral and electroencephalographic procedures.
The workhorse for these manipulations is the TC Helicon VoiceOne processor. Settings are controlled remotely via MIDI commands issued by the stimulus presentation computer. For manipulations that require changes to certain parts of the frequency spectrum, such as formant shifts, both clean and altered signals are filtered, then mixed, before further amplification and presentation back to the subject.
Component set-up by type: mic – amp/audio interface – harmonizer – line level – analog filter – mixer – amp – earphones.
Component set-up by label: DSP – RME – TC Helicon – Ebtech – Wavetek – Behringer – Mackie – Etymotic.
For those that prefer fully digital implementation, effective alternatives include Eventide’s DAW plug-ins like the H300 Factory.