Sound card start-up latency
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Soundcard start-up latency is the time it takes from telling the computer to play a sound to when the sound actually comes out of the speakers or headphones.

Professional musicians have to deal with such issues regularly and a lag over a few milliseconds is considered unacceptable to the trained human ear. Empirical tests have shown that soundcards used in typical psychology studies can have start-up latencies in the hundreds of milliseconds. This can make presentation timing and synchronisation with other equipment a real issue.

For example, Psychology Software Tools (PST) the authors of E-Prime have conducted tests where start-up latencies were anywhere between a few milliseconds to over 350 milliseconds. This is in no way the fault of E-Prime but rather the hardware and operating systems used.

To compound the problem newer operating systems are actually worse than older ones. In the PST tests Windows XP did not have any soundcards with a start-up latency over 20 milliseconds. Windows Vista was averaged over 50 milliseconds and Windows 7 well into the 100's of milliseconds of lag. An excerpt from PST's results is shown below to illustrate the startling range of variation.


Adapter Type Machine Operating System Driver API/Expected Latency Mean (ms) StdDev Min (ms) Max (ms)
Sound Blaster SB0880 X-Fi PCIe Ad Hoc Quad Core Win 7x64 manufacturer DirectSound
344.267
830.216
119.000
3345.000
Asus Xonar DG PCI Ad Hoc Quad Core Win 7x64 manufacturer DirectSound
69.643
1.277
68.000
72.000

Excerpt from PST's research on soundcard start-up latency


You are advised to view PST's full results and watch the video below explaining more about soundcard start-up latency.

Note how in the video a 7 year old soundcard out performs a newer model which is integrated into the motherboard!

A professional DJ shows you what start-up latency is with a practical demo of on-board sound versus
a dedicated soundcard.