I was streaming audio from the Internet and I noticed that when I generated silence for a long period of time in a file and played it on iTunes for example, the silence would be replaced by this weird hiss sound.
I’ve tried saving files in different places to see if it made a difference. I did think it was my iTunes messing with the files, but upon inspection I found out that it happens once I’ve exported a file from Audacity.
I have used the Noise Removal tool, but nothing changes.
There was a bug in Audacity could cause noticeable noise in exported stereo files, which was fixed in September 2013.
Please update to the current version of Audacity (2.0.5) which is available here: http://audacityteam.org/download/
Note that it is normal for “silence” to not remain absolutely silent when exported in 16 bit format (or lower), but the noise level of “silence” (in 16 bit format or higher) should be so low as to not be noticeable. Prior to the fix, the noise level during “silence” was sometimes much greater than it should be.
