The principle cues for judging distance

Intensity of the sound

• amplitude diminishes inversely with distance
• depends on listener's familiarity with the sound

The ratio of reverberated to direct sound

• when the source is close to the listener, ratio of reverb to direct (R/D) is low.
• reflected energy increases with an increase in distance.
• at very large distances, an audio horizon is reached,and distance cannot be discerned.

Amount of high-frequency energy in the sound

• attenuation of a sound wave propagating through the atmosphere is greater at high frequencies.
• at long distances there is perceivable absence of high-frequency components.