Hello,
From your description it appears that your code runs fine when downloaded via SigmaStudio, but not when booting via your uC. I've had similar problems when my uC didn't wait long enough for the DSP to "wake up" before stuffing it with code. More specifically, be sure you're following everything on Page 30 of the data sheet, including polling the PLL lock bit if used. Generally, any deviation from the needed wait times cause the DSP to load incompletely. The usual symptom is no sound, and/or the noise you're experiencing.
Best regards,
Bob