Which cues tell a listener how far away a voice is (level, direct-to-reverberant ratio, high-frequency loss, vocal effort), and with what numbers?

Problem: a clean generated voice sounds 'in the listener's ear' regardless of shot scale; placing it at distance needs the right cues together. Conditions: dialogue or narration to sit at a stated distance in a scene. Method (review of the psychoacoustic literature): (1) Level: in an anechoic field level falls about 6 dB per doubling of distance, less in reverberant rooms (about 4 dB per doubling in one auditorium); level is a relative cue, confounded by source level and directivity. (2) Direct-to-reverberant energy ratio (DRR): direct sound falls 6 dB per doubling while reverberant energy changes only about 1 dB per doubling, so DRR falls with distance and listeners hear that as farther; perception is most accurate when level and DRR are both present. (3) Spectrum: air absorption removes high frequencies, and sounds with less high-frequency content relative to low are judged farther. (4) Speech-specific: vocal effort changes the spectrum (shouted speech has more high-frequency energy than conversational), listeners compare perceived production level with received level, so a 'distant' voice must also sound like the right effort, and distance estimates grow with vocal effort. Failure modes: a fixed DRR-to-distance mapping is not valid because it depends on room and source; a lowpass alone or a level drop alone reads as 'quiet' or 'muffled' rather than 'far'. Limitations: laboratory studies, mostly noise or speech in rooms, not film mixes. Version/date: review published online 2015-11-20. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Numbers are the review's summaries of earlier studies, not film-mix measurements. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4744263/",
      "note": "Level; DRR; Spectrum; Familiarity with speech; Cue combination"
    }
  ]
}