A RT60 longer than 0.6 seconds negatively impacts speech intelligibility mainly due to what?

A RT60 longer than 0.6 seconds negatively impacts speech intelligibility mainly due to what?

• A. Increased Direct Sound Energy
• B. Signal-to-Noise Ratio Improves
• C. More Stable Interaural Time Difference Cues
• D. Smearing of Critical Temporal Information

Answer: (D)

Long reverberation time means reflections keep arriving after the direct sound for a surprisingly long period. Speech depends on precise timing cues—the rapid onsets of consonants, the amplitude envelope of syllables, and the distinct temporal order of sounds. When RT60 is around 0.6 seconds or longer, these cues get smeared as energy from one phoneme overlaps with the next. That temporal overlap softens or disguises the fine timing differences that help identify speech sounds, especially rapid or transient consonants, so words start to blur together and intelligibility drops. The idea isn’t that more direct energy is happening; the opposite is true—the direct-to-reverberant energy ratio decreases as late reflections add background, diffuse energy. And while binaural timing cues can become less reliable in reverberation, the key issue for intelligibility here is the loss of clear temporal information due to smearing, not an improvement in cue stability.

Long reverberation time means reflections keep arriving after the direct sound for a surprisingly long period. Speech depends on precise timing cues—the rapid onsets of consonants, the amplitude envelope of syllables, and the distinct temporal order of sounds. When RT60 is around 0.6 seconds or longer, these cues get smeared as energy from one phoneme overlaps with the next. That temporal overlap softens or disguises the fine timing differences that help identify speech sounds, especially rapid or transient consonants, so words start to blur together and intelligibility drops.

The idea isn’t that more direct energy is happening; the opposite is true—the direct-to-reverberant energy ratio decreases as late reflections add background, diffuse energy. And while binaural timing cues can become less reliable in reverberation, the key issue for intelligibility here is the loss of clear temporal information due to smearing, not an improvement in cue stability.