Sound Finder Lag

When I use the Sound Finder, there is usually a small bit of the beginning of the sound that occurs before the label.

Here is a screenshot of my settings:

And here is a screenshot of the results:

Is this expected behavior?

I am using Ubuntu 18.04
Audacity 2.2.1
Installed from the Ubuntu Software Center

Sound / Silence finder plug-ins are not sample accurate. They analyze the audio in small blocks rather than sample by sample. This is because they are “Nyquist plug-ins” and for Nyquist, looping through every sample would be rather slow whereas looping through the selection is small blocks of sound is much faster. The precision is therefore limited to the size of the blocks (I don’t recall the exact figure, but the blocks are probably about 100 samples long). To ensure that all of the sound lies within the labeled region, set the third control a little higher than zero.

Thanks Steve, that makes sense.

If you need sound / Silence finder to be sample accurate, it would be relatively easy to modify the plug-ins so that the process every sample instead of blocks. These plug-ins are just plain text files, so it’s quite possible for anyone to make the necessary modifications - no need for “compiling source code” or anything highly technical like that. The downside is, as previously mentioned, is that the effects become much slower. For most use cases, the small amount of imprecision is greatly outweighed by the better processing speed.