Audio Delay
Convert distance ↔ delay at the temperature-corrected speed of sound, and compute the alignment delay between two sources (speaker/subwoofer), in milliseconds and in samples at 48 kHz.
Inverse · delay → distance
Type a delay and get the equivalent distance and samples at the current speed of sound.
Distance → delay (at the current temperature)
| Distance | Delay | Samples @Fs |
|---|
row closest to your distance · samples at the selected Fs.
How it is calculated · speed, delay and alignment
1. Speed of sound in air:
c = 331.3 + 0.606·T (m/s), with T in °C. At
20 °C it gives 343.42 m/s; at 0 °C, 331.3 m/s.
2. Path delay:
delay(ms) = distance(m) / c × 1000. Each meter adds
~2.9 ms at 20 °C.
3. Aligning two sources: the
nearer source is delayed by the path difference,
delay = (d_far − d_near) / c × 1000, so both wavefronts
reach the listener together.
4. Samples:
samples = ms/1000 × Fs. At 48 kHz, 29.14 ms
equals 1399 samples.
5. Inverse: given a delay,
distance = c × ms/1000. Handy to read a processor's
delay and find the distance it corresponds to.
6. Simple geometric model: it uses direct distances and ignores reflections, wind, humidity and the DSP's own latency. For subwoofers, measure the real distance from the cone to the listening position.
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How it works
The calculator converts distance into audio delay and back, using the speed of sound corrected for air temperature: c = 331.3 + 0.606·T m/s (343.42 m/s at 20 °C). The travel delay is delay(ms) = distance(m) ÷ c × 1000 —roughly 2.9 ms per meter at 20 °C— and it is also expressed in samples with samples = ms/1000 × Fs, for sample rates from 44.1 to 192 kHz (48 kHz by default, the usual rate in DSP processors).
The alignment mode computes the delay you must apply to the source closest to the listener so its sound arrives together with the far source: delay = (d_far − d_near) ÷ c × 1000. This is the typical adjustment between a subwoofer and tops, or between the main PA and delay towers. The model is simple geometry: it does not account for reflections, wind, humidity or the internal latency of the DSP.
Example: aligning a subwoofer at 4 m with a top at 1.5 m
- At 20 °C the speed of sound is
331.3 + 0.606 × 20 = 343.42 m/s. - Path difference:
4 − 1.5 = 2.5 m. - Delay for the near source (the top):
2.5 ÷ 343.42 × 1000 = 7.28 ms. - In samples at 48 kHz:
0.00728 × 48,000 ≈ 349 samples.