[Nevod]

While listening to my modded Fostex, I have noticed some sibilants on "ss" and "th" sounds, though not all the time. However, when I performed some tests with Sinegen, there was no noticeable peaks in 5-9kHz region, and pretty much anywhere else, everything mostly conformed to equal loudness curves. There were only peaks at 11 kHz and 900Hz. 
So, I concluded that it may be at lesat partially due to the songs themselves. But to be sure, I'd ahve to check the sound material without effects of the playback equipment. The only way to do it, as I see, is to open the sound file in some editing program and peek at the waveform/spectrogram/etc. 
However, I don't know exactly how to do it. Is there any advice or maybe an article or even some course on that?
Thanks!

 

[Head Injury]

See if there's a spectrum analyzer plugin for the software player you use.

 

[LFF]

Quote:

While listening to my modded Fostex, I have noticed some sibilants on "ss" and "th" sounds, though not all the time. However, when I performed some tests with Sinegen, there was no noticeable peaks in 5-9kHz region, and pretty much anywhere else, everything mostly conformed to equal loudness curves. There were only peaks at 11 kHz and 900Hz. 
So, I concluded that it may be at lesat partially due to the songs themselves. But to be sure, I'd ahve to check the sound material without effects of the playback equipment. The only way to do it, as I see, is to open the sound file in some editing program and peek at the waveform/spectrogram/etc. 
However, I don't know exactly how to do it. Is there any advice or maybe an article or even some course on that?
Thanks!

You need to look at a spectrogram. Sibilance shows up as a fuzzy patch starting at around 4.5kHz. It will take some time learning what it looks like and what the variations look like but at least you know that you can actually confirm it visually.