mac become no sound when after mac sleep Sometime, I close lid, and open again, The sound not available.

When I restart my mac, The sound back.

Is this a bug?
Yes, the same bug I have from time to time, too.
I could fix it without a reboot by reloading the kernel extension for audio with these commands:

sudo kextunload /System/Library/Extensions/AppleHDA.kext
sudo kextload /System/Library/Extensions/AppleHDA.kext