Direct-to-reverberant energy ratio sensitivity

Area of Science:

• Psychoacoustics
• Auditory Perception
• Acoustics

Background:

• The direct-to-reverberant (D/R) energy ratio is a key acoustic cue for perceiving sound source distance.
• Human sensitivity to variations in the D/R ratio, crucial for distance perception, remains largely unquantified.

Purpose of the Study:

• To measure human listeners' discrimination thresholds for the D/R energy ratio.
• To investigate how different sound stimuli affect the perception of D/R ratio changes.
• To determine the precision of D/R ratio as a cue for sound source distance.

Main Methods:

• Six listeners participated in a study using virtual sound source techniques.
• Direct-to-reverberant energy discrimination thresholds were measured using an adaptive 2-alternative forced choice (2AFC) procedure.
• Four stimulus types were tested: noise bursts (abrupt/gradual onset/offset), speech, and impulse sounds, across a 0-20 dB D/R range.

Main Results:

• Discrimination thresholds for the D/R ratio were consistently between 5 to 6 dB across all tested stimuli.
• Psychometric function slopes were homogeneous, indicating consistent listener performance regardless of stimulus type.
• These thresholds suggest the D/R ratio alone provides coarse, rather than fine, coding of sound source distance.

Conclusions:

• The D/R energy ratio requires substantial physical distance changes (over 2-fold) to be reliably discriminated by listeners.
• Perceptual coding of sound source distance based solely on the D/R ratio is imprecise.
• Further research is needed to explore how other acoustic cues interact with the D/R ratio for more accurate distance perception.