Group Delay Transients (but not exact)
Group delay is the negative of the derivative of the phase curve with respect to radian frequency. So in loose terms, it’s in direct correlation to phase at different frequencies. Group delay (GD) is measured in milliseconds (ms).
- Phase is measured in radians.
- Radian frequency is measured in radians / second.
- As a result, GD has units of time (seconds, most likely, milliseconds).
In other words, GD is a measure of how fast the acoustic phase changes at different frequencies. It tells how well time relationships between a small group of frequencies are preserved in a narrow frequency region, around the point in frequency where the group delay is evaluated.
Best thresholds
| Frequency (kHz) | Threshold (ms) | Periods (Cycles) |
|---|---|---|
| 0.5 | 3.2 | 1.6 |
| 1 | 2 | 2 |
| 2 | 1 | 2 |
| 4 | 1.5 | 6 |
| 8 | 2 | 16 |
The best thresholds of audibility table has been provided by Blauert and Laws
from Audio Judgement
- 1 kHz and above – anything less than 2 ms is good.
- 200 Hz – 1000 Hz – less than 4 ms.
- Under 200 Hz – Expect higher numbers. Even 30-40 ms for the very low frequencies.
0.6ms 3ms at 500Hz 5ms at 250Hz
From testing (or experience)
- Speaker with 30ms @ 50Hz and 10ms @ 60Hz is some what on the threshold of acceptable.