I mostly ask as a curiosity, since I'm not noticing any other "negative" effects.
Recently I found that my PS4 no longer makes the audible "beep" noise when coming out of Rest mode. I assume this also applies to turning on (I'm just not able to test at the moment).
Don't get me wrong, I'm definitely not complaining at all.
I read through the last few update notes (I update pretty regularly) and didn't see anything mentioned. There are other posts online that have the same issue, usually just a broken speaker, which I figure is probably the issue here as well. Doesn't hurt to double check though.
My disc drive has begun acting finicky as well, so I figure I'm just seeing some symptoms of an aging system start to crop up.
Best Answer
As of December 2nd 2019, I can confirm the PS4 still beeps when coming out of rest mode. I played my PS4 last night, and it beep when I pressed the power button on my controller to turn it on. I know my PS4 has the latest firmware, since I upgraded the internal hard drive within the last month.
By the sound of it, as you already noted, your PS4 might have a hardware problem. If it's just the speaker, then you shouldn't have to worry too much as far as I can tell. On the contrary, it could more than just a broken speaker.
Recently, I experienced the exact opposite of the issue you describe. For quite some time, my PS4 would randomly beep at unexpected moments (and even occasionally shutoff) while it was in rest mode. After doing some investigation, my research lead me to one of two problems
With that information, I decided it was time to replaced the hard drive since the internal hard ware had not been upgraded in 5 years. Upon replacing the drive, the PS4 went back to functioning normally and the extra beeping/randomly shutting no longer happened.