Early room reflections benefit speech intelligibility as much as raised direct sound level

Evidence

Lochner and Burger (1958), Soulodre et al. (1989) and Bradley et al. (2003) found that multiple room reflections contribute to improved speech intelligibility. The most elaborate of these experiments used an array of eight loudspeakers in an anechoic chamber to simulate early reflections and a reverberant decay for several different rooms (Bradley et al., 2003). The result was that early reflections (>50 ms) had the same desirable effect on speech intelligibility as increasing the level of the direct sound. Remarkably, even attenuating the direct sound had little effect on intelligibility in a sound field with sufficient early reflections. — Toole, Floyd E, Sound reproduction- the acoustics and…, 557

Categorization

• XREF: This overturns the instinct that room reflections are only a problem; relates to the book’s broader ‘listeners adapt to rooms’ argument. — connects to: Speech intelligibility in rooms can be predicted from fluctuation strength — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 2059; Early reflections boost perceived loudness while loud late reverberation degrades intelligibility — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 273; Early reflections within 30-40 ms improve speech intelligibility — , Toole, Floyd E - Sound reproduction-…, 824 (+5 more)
• corroborated: 2 independent passages support this claim — Toole, Floyd E, Sound reproduction- the acoustics and…, 557

Broader Connections

• Early reflections within 30-40 ms improve speech intelligibility #corroborates (0.92) — , Toole, Floyd E - Sound reproduction-…, 824
• Speech intelligibility depends on high direct-to-reverberant sound ratios #complicates (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2434
• Direct sound carries signal information uncontaminated and governs speech intelligibility #complicates (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1729
• Speech intelligibility gains more from reducing masker energy than from increasing target energy #expands (0.75)
• Small playback rooms impose their own early reflections on recorded sound #expands (0.75)
• Adding more loudspeakers can worsen speech intelligibility by shrinking critical distance #expands (0.72) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2454