Speaker energy aimed at rear walls degrades intelligibility via reflection and interference

Evidence

The direct component is important because it carries the information in the signal in an uncontaminated form. Therefore a high level of direct sound is required for a clear sound and good intelligibility of speech. The direct sound also behaves in the same way as sound in free space, because it has not yet interacted with any boundaries. This means that we can use the equation for the intensity of a free space wave some distance from the source Figure 6. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1729 (#expands, via linked claim)

Early reflections, for speech up to about 60 ms and for music up to about 100 ms, increase the loudness of sound. Early reflections also strongly contribute to spatial perception, such as in the estimation of room size and source distance. Late reverberation, if too loud, decreases intelligibility of speech or fast passages of music. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 273 (#corroborates, via linked claim)

The direct sound: This is the sound that carries information and articulation. For speech it is important that the listener receive a large amount of direct sound if they are to comprehend the words easily. Unfortunately, as discussed in Chapter 1, the direct sound gets weaker as it spreads out from the source. Every time you double your distance from a sound source the level of the direct sound goes down by a factor of four, that is, an inverse square law. Thus the further away you are from a sound source, the weaker the direct sound component. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2434 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Phantom center images reduce speech intelligibility due to interaural crosstalk; Adding more loudspeakers can worsen speech intelligibility by shrinking critical distance — David Howard, Jamie Angus, coustics and Psychoacoustics, 2454; Direct sound carries signal information uncontaminated and governs speech intelligibility — David Howard, Jamie Angus, coustics and Psychoacoustics, 1729 (+6 more)

Broader Connections

• Direct sound carries signal information uncontaminated and governs speech intelligibility #expands (0.90) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1729
• Speech intelligibility depends on high direct-to-reverberant sound ratios #corroborates (0.85) — David Howard, Jamie Angus, coustics and Psychoacoustics, 2434
• Early reflections boost perceived loudness while loud late reverberation degrades intelligibility #corroborates (0.85) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 273
• Room boundaries alter loudspeaker output through reflected image sources #expands (0.80)
• Near-wall listening positions create early strong rear reflections #expands (0.80)
• Room reverberation barely affects early reflection audibility but strongly elevates late-reflection thresholds #complicates (0.75) — Toole, Floyd E, Sound reproduction- the acoustics and…, 630
• Increasing speaker directivity reduces the reverberant field like a tone control does #qualifies (0.75)