Delay Line (Audio)
Definition
Delay Line (Audio)
An audio delay line adds a precise time offset to a signal path, measured in milliseconds. In sound system design, delays align the arrival time of multiple speakers so sound reaches the listener simultaneously from all sources. The required delay equals the distance difference divided by the speed of sound (approximately 343 m/s at 20°C). SonaVyx calculates optimal delay from measured arrival times.
Delay (ms) = distance (m) / 0.343, or equivalently distance (ft) / 1.125
How It Is Measured
The required delay between speakers is measured using the SonaVyx impulse response or transfer function, which reveals the arrival time of the direct sound from each speaker. The time difference between the early and late speaker determines the delay to apply to the closer speaker. SonaVyx delay finder automatically identifies the optimal delay from the cross-correlation peak.
Practical Example
A front-fill speaker is 8 meters closer to the first row than the main PA. Without delay, the fill arrives 23.3 ms early, creating confusing precedence and comb filtering. SonaVyx measures the arrival time difference and recommends 23.3 ms delay on the fill. After applying delay, the transfer function shows coherence rising from 0.4 to 0.9 at the overlap region, confirming time alignment.
Speed of Sound
The speed of sound varies with temperature: approximately 331 m/s at 0°C and 343 m/s at 20°C, increasing by about 0.6 m/s per degree Celsius. For outdoor events where temperature changes significantly during the day, delay settings may need adjustment. A 10°C temperature change shifts timing by approximately 1.7%, which is audible in precision-aligned systems.
Haas Effect and Delay
The Haas effect (precedence effect) causes listeners to perceive the direction of sound from the first-arriving source, even if a delayed source is up to 10 dB louder. In PA systems, delaying fill speakers by 5 to 15 ms beyond arrival-time alignment (adding excess delay) ensures the listener perceives sound as coming from the main system while receiving reinforcement from the fill. This maintains natural directional cues.
Zone Delay
Large venues use multiple speaker zones with progressive delay to create a coherent wavefront that sweeps through the audience. Each successive zone receives additional delay corresponding to the propagation time from the main speaker to that zone's position. SonaVyx measures the required delay per zone by identifying the direct sound arrival from both the main system and the zone speaker at each position.
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