I am running am embedded linux kernel 3.14.28-1.0.0 built using Yocto. It is running on a Boundary Devices Nitrogen6x board. I am playing sound using aplay, and the sound device is a sgtl5000.
**** List of PLAYBACK Hardware Devices ****
card 0: imx6qnitrogen6s [imx6q-nitrogen6_som2-sgtl5000], device 0: HiFi sgtl5000-0 
Subdevice #0: subdevice #0
Exactly 5 seconds after any sound has finished playing, there is a short (around a half second) of very faint noise. The sound is similar to rubbing ones finger across a piece of paper.
I'm not exactly sure what is causing the sound, and whether it is coming from aplay, the sgtl5000 driver, power to the chip, etc. My guess is that there is a 5s timeout that cuts power to the chip, but I'm not sure if this is from the power management side of things or other 5s power or suspend timeout. I would like to get rid of the noise, and I have tried disabling suspend in the sgtl5000.c and ac97_bus.c files, but it still makes the sound.
Does anyone have any idea what would be causing this, and how I can get rid of it?