Acoustical and Psychoacoustic Properties for Mono Sound Walk

• Explore how sound changes with distance in a mono mix
• Identify psychoacoustic cues that suggest depth and movement
• Apply these cues in the Mono Sound Walk project
• Practice strategies to simulate space without stereo

Distance Illusion: Guess the Distance

• I will play the same mono clip three times: take A, take B, take C.
• Your task: identify which take is farthest and estimate the distance bin.
• Bins to choose from: 1–3 m, 4–8 m, 10–20 m.
• Listen for three cues: level change, high-frequency roll-off, and the direct-to-reverberant balance.

Click to watch a short demo on distance perception in mono sound.

Acoustical Properties of Distance Perception

• Loudness drops as the source moves farther away
• High frequencies fade first, making distant sounds more muffled
• Reverberation builds up in enclosed or reflective spaces
• Direct-to-reverberant balance shifts: more reflections = more distance

Quick Calculator Demo: Inverse-Square Law

• Try −6 dB per doubling of distance
• Start: 1 m at 70 dB
• 2 m ≈ 64 dB
• 4 m ≈ 58 dB
• 8 m ≈ 52 dB

Resources (open one live):

• Sengpiel Audio: Distance Law Calculator
• WKC: Inverse-Square Law Sound Calculator

Automation Essentials in REAPER

• Linear: smooth, constant-rate change
• S-Curve (Slow Start/End): gradual entry and exit
• Fast Start: steep change at the beginning, flattens later
• Fast End: flat at first, steep change at the end
• Square: instant jump, no transition
• Bezier: fully customizable shape for precision

Resources:

• Kenny Gioia: Automation Basics (YouTube)
• Automation Review

Automation Demo: Write, Touch, Latch

• Try Write mode: captures every move live
• Touch: adjusts only while fader is touched
• Latch: holds last change until stopped
• Practice: automate volume for a car “approach and pass-by” in mono

Volunteer to try volume automation?

Frequency Response (High-Frequency Roll-off)

• High frequencies attenuate faster than low frequencies.
• Distant sounds lose high frequencies, creating a “muffled” effect.
• Use low-pass filtering to replicate distant sounds.

Volunteer to try low-pass filtering?

Reverberation and Distance

• Near sounds: dry, minimal reverb, bright and clear
• Far sounds: more reverb, muffled, less direct energy
• Adjust wet/dry ratio and EQ to simulate depth
• Reverb should match the environment (small room, hall, outdoors)
• Direct-to-reverberant balance is a key distance cue

Direct-to-Reverberant Ratio (DRR)

• DRR = balance of direct sound vs. reverberant sound
• As DRR decreases, perceived distance increases
• High DRR → close, present, detailed
• Low DRR → far, diffuse, less intelligible

Resources:

• Intro to DRR – Montana State Univ.
• Review of Auditory Distance Cues (Larsen et al.)

Convolution Reverb for Believable Rooms

• Load real room impulse responses (IRs) into ReaVerb
• OpenAIR: free architectural IRs → realistic halls & rooms
• Samplicity M7: musical, smooth reverbs → great for creative use
• Apply: same mono sound at three “distances”
  • Near: short IR, low wet, bright EQ
  • Mid: medium IR, moderate wet, mild HF roll-off
  • Far: long IR, high wet, strong HF roll-off

Resources:

• OpenAIR Impulse Response Library
• Samplicity Bricasti M7 IR Pack

Starting Reverb Settings for Distance

• Close proximity: Short reverb time, low wet/dry mix.
• Medium distance: Moderate reverb, slight high-frequency damping.
• Far distance: Long reverb, heavy high-frequency roll-off.
• Adjust pre-delay for spatial reflection.

Advanced Automation: Tail and Pre-delay

• Tail length: Adjust reverb tail for room size.
• Pre-delay: Automate for proximity changes.
• Combine wet/dry and pre-delay for complex depth.
• Simulate large spaces with longer reverb tails.

Volunteer to try reverb?

Practice Tips for Simulating Distance with Echo or Delay Automation

• Use echo/delay to create a sense of distance
• Adjust delay time for close or distant effects
• Modify feedback to simulate multiple reflections
• Combine delay with reverb for natural depth

Suggested Starting Settings for Delay Automation

• For close proximity (1-3 meters): 10-50 ms delay, 10-20% feedback
• For medium distance (3-10 meters): 50-150 ms delay, 30-40% feedback
• For long distance (10+ meters): 200-500 ms delay, 50-80% feedback
• Automation curves: adjust for linear or fast changes

Volunteer to try delay?

Motion and Dynamic Cues

• Changing sound level or frequency suggests movement.
• The Doppler effect simulates pitch changes as sound moves.
• Adjust sound properties dynamically to reflect movement.

Volunteer to try Doppler effect?