Speech needs at least 7.5 dB signal-to-noise ratio for adequate intelligibility

Evidence

From this figure, we can see that a speech to background noise ratio of greater than +7.5 dB is required for adequate intelligibility. Ideally, a signal-to-noise ratio of greater than 10 dB is required for very good intelligibility. This assumes that there is minimal degradation due to reverberation. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2476

Categorization

• XREF: Connects to the reader’s prior work on noise and silence — a concrete quantitative threshold for when ambient noise destroys the comprehension of speech.