how can i tell

[ethan hines]

if there really is a difference in latency. I have a usb creative audio audigy is there a testing program?

[Michael Tippach]

Apart from mere numbers, the best testing program is a good pair of ears ;D

One way to find out: Connect the inputs of your soundcard directly to the outputs. Use your favourite audio software to create a feedback loop. The frequency of the audio-feedback is the inverse of the round trip latency, e.g. if the frequency is around 100Hz this would mean you have a round trip latency (input+output) of 10ms.

If you want it a little more sophisticated, create a single audio-pulse which you would then re-record. The recorded pulse will be off by Xms WRT to the original. To that you have to add the latencies as displayed by your audio application for both input and output. This is because some audio applications perform automatic latency compensation while others do not. The resulting value is your round trip latency.

It is close to impossible to measure input and output latency independently without some sort of special hardware available.

[Dino Cazares]

In my opinion, the best way to tell how much latency there is, is to connect an instrument or microphone to the soundcard and monitor the input.
For example, you could connect a simple microphone to the MIC input in your soundcard, use some ASIO compatible program that can do INPUT monitoring via ASIO and start speaking to the microphone.
If while speaking, it seams as the recorded sound was coming with delay/echo, than the latency is quite high, there will be a feeling of echo or feedback.
To make the monitoring be more realtime, you should lower the ASIO4ALL latency value.
Hope this is useful.