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Audio Delay & Echo Time Calculator

Calculate audio delay time in milliseconds from BPM and note value — quarter, eighth, dotted, triplet. Also computes acoustic propagation delay from speaker distance for live sound alignment.

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Formula

tbeat=60000/BPMms,tprop=d/c×1000t_beat = 60000/BPM ms, t_prop = d/c × 1000
BPM— Beats per minute (bpm)
c— Speed of sound (m/s)

How It Works

This calculator computes audio delay time for tempo-synchronized effects and acoustic propagation alignment. Music producers, live sound engineers, and studio technicians use it to synchronize delay effects with song tempo and align speaker systems for coherent sound. For tempo-synced delays, time equals 60000/BPM milliseconds per beat, with subdivisions scaled proportionally: quarter note = 60000/BPM, eighth = 30000/BPM, sixteenth = 15000/BPM. For acoustic propagation, sound travels at 343 m/s (at 20C per ISO 9613-1), creating 2.92 ms delay per meter. According to Haas effect research (1951), delays under 30 ms fuse perceptually with the original sound; 30-50 ms creates spatial widening; above 50 ms produces distinct echoes. Live sound systems using delay speakers require 10-20 ms additional 'precedence delay' beyond propagation time to maintain localization to the main PA per Meyer Sound and d&b audiotechnik guidelines.

Worked Example

Problem: Calculate delay settings for a live PA with delay speakers at 25 m from main system, plus tempo-synced delay effect at 132 BPM.

Solution - Acoustic delay for speaker alignment:

  1. Propagation distance: 25 m
  2. Speed of sound at 20C: 343 m/s (per ISO 9613-1)
  3. Propagation time: t = 25/343 * 1000 = 72.9 ms
  4. Add precedence delay: +15 ms (Haas effect - ensures main PA perceived as primary source)
  5. Final delay setting: 72.9 + 15 = 87.9 ms
Temperature correction for outdoor event at 30C:
  • c = 331.3 + 0.606 * 30 = 349.5 m/s
  • Propagation time: 25/349.5 * 1000 = 71.5 ms
  • 1.4 ms faster than 20C calculation - significant for time-alignment
Solution - Tempo-synced delay effect at 132 BPM:
  1. Quarter note delay: t = 60000/132 = 454.5 ms
  2. Eighth note: 454.5/2 = 227.3 ms
  3. Dotted-eighth (classic U2 'Edge' delay): 454.5 * 0.75 = 340.9 ms
  4. Sixteenth note: 454.5/4 = 113.6 ms
  5. Triplet-eighth: 454.5/3 = 151.5 ms
Common musical delay relationships:
  • Dotted values add 50% (eighth * 1.5 = dotted-eighth)
  • Triplets divide by 3 instead of 2
  • Half note = 909.1 ms, whole note = 1818.2 ms at 132 BPM

Practical Tips

  • ✓Tempo-synced delay reference chart at 120 BPM: whole = 2000 ms, half = 1000 ms, quarter = 500 ms, dotted-quarter = 750 ms, eighth = 250 ms, dotted-eighth = 375 ms (the 'Edge' delay), sixteenth = 125 ms. Scale linearly: at 140 BPM multiply all by 120/140 = 0.857 (dotted-eighth becomes 321 ms).
  • ✓In live PA, use measurement software (Rational Acoustics Smaart, SysTune, AFMG SysTune) to verify time alignment via impulse response measurement. Position the measurement mic at the overlap zone between main and delay coverage. Target alignment within +/-0.5 ms for frequencies above 1 kHz per Meyer Sound guidelines.
  • ✓For distributed speaker systems (convention halls, airports, worship spaces), delay each zone relative to the furthest upstream speaker. Calculate cumulative delay: Zone 1 at 0 ms, Zone 2 at D12/343 + 15 ms precedence, Zone 3 at (D12+D23)/343 + 15 ms, etc. Missing one zone in the chain causes speech intelligibility to drop 20-40% per RASTI measurements.
  • ✓Temperature compensation rule-of-thumb: sound speed changes 0.18% per degree Celsius. For a 30 m delay speaker, each 5C temperature change shifts alignment by 0.8 ms. Program delay systems to adjust automatically or check/recalibrate when temperature varies more than 10C from initial setup.

Common Mistakes

  • ✗Setting delay speaker timing to exact propagation time - this creates equal-amplitude arrivals from main and delay speakers, causing comb filtering with +/-6 dB frequency response ripple. Add 10-20 ms 'precedence offset' per Haas effect guidelines to ensure main system arrives first and dominates localization perception.
  • ✗Ignoring temperature effects on sound speed - c = 331.3 + 0.606*T (Celsius) m/s per ISO 9613-1. At 35C outdoor: c = 352 m/s (2.6% faster than 20C). For a 50 m throw, this changes propagation time by 3.8 ms - enough to cause audible comb filtering if not corrected. Professional systems (Meyer Galaxy, d&b ArrayCalc) include temperature compensation.
  • ✗Confusing tap tempo interval with note division - tap tempo pedals calculate interval directly from tap timing. A 500 ms tap at quarter-note division displays 120 BPM; the same 500 ms at eighth-note division displays 240 BPM. Verify the output waveform against a metronome if unsure which mode is active.
  • ✗Applying Haas effect delays in control room monitoring - studio engineers sometimes add 15-30 ms delay to one channel for width, creating localization issues that translate poorly to other playback systems. Per AES/EBU guidelines, monitor in true stereo without artificial delays; use pan and level for width.

Frequently Asked Questions

t = 60000/140 = 428.6 ms per quarter note. Common subdivisions at 140 BPM: dotted-eighth (the most musical delay for modern genres): 428.6 * 0.75 = 321.4 ms. Eighth note: 428.6/2 = 214.3 ms. Sixteenth note: 428.6/4 = 107.1 ms. Triplet-eighth: 428.6/3 = 142.9 ms. For EDM/pop production, dotted-eighth or sixteenth delays create rhythmic motion without cluttering the mix.
Per Haas/Wallach precedence effect research (1951): 0-10 ms - sounds fuse completely, delayed signal adds loudness only. 10-30 ms - fusion with spatial 'widening' or 'thickening'. 30-50 ms - coloration begins, comb-filter effects audible, location uncertain. 50+ ms - discrete echo perceived as separate event. The threshold varies with signal type: transients (drums, speech) reveal echoes earlier (~35 ms) than sustained tones (~60 ms). In reverberant rooms, reflections mask discrete echoes, raising the threshold to 60-80 ms.
1. Calculate propagation time: 25 m / 343 m/s * 1000 = 72.9 ms at 20C. 2. Add precedence delay: +10-20 ms (start with +15 ms) to ensure main PA wins localization. 3. Set delay processor to 87.9 ms total. 4. Verify with measurement: use Smaart or similar to measure impulse response at overlap zone; main PA impulse should arrive 10-20 ms before delay speaker impulse. 5. Temperature-correct: at 30C, propagation is 71.5 ms (total becomes 86.5 ms). Level delay speaker 3-6 dB below main at overlap zone per d&b audiotechnik design guidelines.

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