It's About Time: Minimizing Hardware and Software Latencies in Speech Research With Real-Time Auditory Feedback.
Kwang S Kim, Hantao Wang, Ludo Max
PMID 32640180WHAT IT FOUND
Real-time speech feedback delays are much larger than usually reported, ranging from 19 to 39 ms depending on hardware.
Using a manufacturer's own driver and specific software settings can cut this to 11.4 ms. Clinicians using this tech must measure the total loop delay, not just the software processing time.
Key findings
01Total feedback loop latency, which includes both hardware and software delays, ranged from approximately 19 ms to 39 ms across tested setups, significantly higher than the 10-15 ms often claimed in published studies.
02Using the audio interface manufacturer's own driver instead of the generic ASIO4ALL driver consistently resulted in shorter and more stable hardware latencies.
03Optimizing software parameters (lowering nDelay) and using low-latency hardware (RME Babyface Pro) reduced the total feedback loop latency to 11.4 ms without compromising formant tracking accuracy.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study only tested Windows computers; results may differ on Mac or Linux. Only formant-shift perturbations were tested; other types like pitch-shift may have different latency profiles. The study used a single male speaker's recorded voice for the latency tests, not live human speech.
Declared interests
The research was supported by grants from the National Institute on Deafness and Other Communication Disorders and the Canadian Institutes of Health Research. The authors did not declare commercial conflicts of interest, but they evaluated specific commercial hardware brands.
The easy way to misread this
Do not assume that a faster computer or a newer operating system will reduce feedback delay. The study found that hardware choice, driver selection, and specific software parameter settings were the only factors that significantly lowered latency.