If I play the following 12800 long sample on
GB sound channel 3...

SineWaveSample:
REPT 400
DB $8b,$df,$ff,$db,$84,$20,$00,$24
DB $8b,$df,$ff,$db,$84,$20,$00,$24
ENDR

... then I get the results that are shown here:

As can be seen from the gif, the top sine wave appears relatively normal but the lower wave has a weighted appearance
depending on the sample values.

The top wave has a small noise spike after reloading of wave RAM is complete but the bottom wave has a very large spike.
This spike accounts for the very heavy buzz sound heard in these samples.

During the 'sample reload period' when snd chnl 3 is disabled the effective value being output is 7 1/2.

Also notice that the very first sample is identical to the last COMPLETE sample that was output before snd chnl 3 was turned off
for reload.

Due to these artifacts there is a tremendous amount of distortion on the sound playback on older GB full-size models and a smaller
amount (but still significant) in all late model older full-size GBs, GB Pockets, and GB Colors units.

It appears to me that snd chnl 3 was never designed for dynamic reload/updates in order to play raw audio samples due to the
side-effects of doing that are described above.

Jeff