Calculate audio delay from distance, speaker alignment, BPM, and temperature to find milliseconds, matching distance, and tempo offsets.
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Audio Delay Formula
The calculator uses the speed of sound at the selected temperature, then converts between distance, delay time, BPM, and arrival-time differences.
- v = speed of sound in meters per second
- T_C = air temperature in degrees Celsius
- delay_ms = audio delay time in milliseconds
- d = distance in meters
- v = speed of sound in meters per second
- delay_to_add_ms = delay needed to align two arrivals
- d_A = first speaker distance in meters
- d_B = second speaker distance in meters
- v = speed of sound in meters per second
- BPM = tempo in beats per minute
- quarter_note_ms = length of one quarter note in milliseconds
- M = note multiplier, such as 1 for quarter note, 0.5 for eighth note, or 0.25 for sixteenth note
- selected_delay_ms = delay time for the chosen musical note value
- distance = sound travel distance matching that delay time
Distance to delay: Use this when you know how far sound travels and need the matching delay time.
Main plus delay speakers: Use this when two speaker systems reach the same listener position at different times. The calculator finds the arrival difference and tells you which source should be delayed.
Tops plus subs alignment: This uses the same arrival-time difference formula, but labels the two distances as tops and subs.
BPM to distance: Use this when you want a musical delay value, such as an eighth note at a given tempo, converted into time and equivalent sound travel distance.
Common Sound Travel Times
These values use a typical indoor speed of sound near 72°F, about 344.8 m/s. Actual values shift slightly with temperature.
| Distance | Approximate delay | Common use |
|---|---|---|
| 1 ft | 0.88 ms | Small speaker or driver offset |
| 10 ft | 8.84 ms | Short stage or room offset |
| 25 ft | 22.10 ms | Small delay speaker zone |
| 50 ft | 44.20 ms | Larger delay speaker offset |
| 100 ft | 88.41 ms | Long throw or outdoor spacing |
Musical Delay Multipliers
| Note value | Multiplier of quarter note | Delay at 120 BPM |
|---|---|---|
| Whole note | 4 | 2000 ms |
| Half note | 2 | 1000 ms |
| Quarter note | 1 | 500 ms |
| Dotted eighth | 0.75 | 375 ms |
| Eighth note | 0.5 | 250 ms |
| Sixteenth note | 0.25 | 125 ms |
Example Audio Delay Calculations
Example 1: Convert speaker distance to delay
You have a speaker that is 50 ft from the listener. Use the indoor default temperature of 72°F.
Convert 50 ft to meters:
At about 344.77 m/s:
The delay time is about 44.20 ms.
Example 2: Convert BPM to distance
You want the distance that matches a quarter-note delay at 120 BPM using the indoor default temperature.
The quarter-note delay is 500 ms, matching about 172.39 m or 565.58 ft of sound travel.
FAQ
Why does temperature matter for audio delay?
Temperature changes the speed of sound. Warmer air carries sound faster, so the same distance produces a slightly shorter delay. Colder air carries sound more slowly, so the same distance produces a slightly longer delay. For many indoor setups the difference is small, but for outdoor sound systems or long distances it can be noticeable.
Which speaker should get delay when aligning two sources?
Delay the source that arrives first at the reference listening position. If the main speaker sound arrives before the delay speaker sound, add delay to the main. If the delay speaker arrives first, add delay to the delay speaker. The goal is to make both arrivals reach the listener at the same time.
Is 1 foot always equal to 1 millisecond of audio delay?
No. The common shortcut is close, but not exact. At typical room temperature, sound travels about 1.13 ft per millisecond, so 1 ft is about 0.88 ms. The 1 ft per 1 ms shortcut can be useful for rough estimates, but precise alignment should use the calculated value.
