SCP Foundation

First off, I'm not sure what you mean by "in between fifteen main walls". If you're referring to the thickness of the walls or their rating for sound-proofing, I'd recommend phrasing it as something like "is to be kept in a soundproof room with an STC rating of at least 60".

"unless when authorized" is an unnatural way to phrase it; it should be "unless authorized" or "without authorization by". "a member of the 05 council" is also a bit odd for an SCP report. Simplifying both phrases into something like "without O5 authorization" (note that it's O5 with the letter O, not the number 0) would sound better. All that said, anything contained within the containment procedures can be assumed to be under the authority of the O5 Council, so mentioning them shouldn't be necessary.

The next sentence is a little confusing… Is there a reason that a person would attempt to make sounds in the SCP's presence? Everyone working with the SCP will have read the report and will be aware of its effects, so even in the event of a containment breach, I imagine they'd do their best to remain quiet. If you want a main focus to be what happens to people when they make sounds near the SCP, I'd recommend adding the fact that people within a certain range of it feel compelled to be heard by it, and adding a way to counter this in the containment procedures. Maybe house the SCP in a vacuum chamber. How such people are handled is also a little strange… Being demoted to D-Class isn't a common punishment, and it's particularly strange if they're also about to be killed via oxygen deprivation. I'd also recommend moving "in case of containment procedure failure, do this"-type instructions to the very end of the section, because it helps to know the full procedure before knowing what to do if it fails.

What's the reason for all the cameras, heat sensors, and movement sensors? Putting the SCP behind a door with a high enough clearance level should dissuade most attempts to interact with it, and the Foundation doesn't install more security than is necessary for any given object. If you want to keep these in, you should provide a reason why each was installed, though I'd recommend cutting them out.

There's no need to specifically say that Class C personnel should do maintenance on the container. It's likely something too complex to assign to a D-Class, and C covers the majority of other personnel in the facility, from researchers and security to maintenance workers, so there's no need to point this out.

By "communicate between signals", are you referring to using non-verbal communication? Maybe specify that they're to use hand signals, or communicate electronically. I'm not sure what you mean in the next sentence; will the SCP turn to face a direction it heard a sound from before attacking? You should clarify this point, and also make it more clear what kinds of sounds the SCP is triggered by. For example, dismantling a defective soundproof panel would likely make at least a little noise. Does that count, or does it have to be an animal noise, like speaking, clearing your throat, your stomach rumbling? This is also the second time you've mentioned Protocol-XXXX-1, but what this entails isn't outlined anywhere.

Next, you mention maintenance on speakers, but this is the first time you're referring to them. If these speakers are important to the SCP's containment, they should be mentioned early in the section, alongside the soundproof walls. Is this referring to the same speaker mentioned in the next paragraph? As I understand it, this speaker is used to force the SCP to teleport into a containment area (although this could be more clear), and it then self-destructs. Why would an object designed to be used once and then self-destruct need maintenance? I assume that you're referring to two separate speakers, but the way it's written is a little confusing. I'm also not sure why the Foundation would've designed that speaker to self-destruct; couldn't it be used to contain the SCP itself, just by playing a sound loud enough to prevent the SCP from hearing anything else?

"weirdly-shaped" is kind of an amateurish way to refer to something. You should start by specifying what kind of skull it is (I would assume human), and then go on to state what makes it unusual. You should go into enough detail that the reader will have a clear mental image of what this skull looks like, including where on it the holes you mention are.

Data is only expunged when it is permanently deleted from the record. This is usually done when the information itself is hazardous in some capacity. The word you should use is "redacted", but in this case, I don't think it's warranted. There's no reason the person reading the report shouldn't know what specific species or civilization went extinct, unless you can tie it to another piece of information that you have a good reason for redacting. Similarly, the location the SCP was discovered in and the year it dates back to (which is something you should be able to explain how the Foundation knows) don't need to be withheld, unless you intend to include a reason in the report for this to be the case. You should probably put more focus on the idea of the skull teleporting from creature to creature, and how quickly large groups can be killed in this way

I don't think there's a need to classify the person or object the skull is attacking as SCP-XXXX-A, mainly because they will be dead before anyone has a chance to file a report. There's also no need to specify "exactly 5:02 minutes" or "3:04:13 seconds", unless those amount of time is relevant in some way, in which case you should make that clear. Saying "approximately five minutes" should be fine, and I'm not even sure how you would determine whether someone has fallen into a coma in less than three seconds. I'd also recommend that you go into more detail on the kind of hallucinations reported.

On the subject of SCP-500, I think it's best to just cut this part out entirely. There is a limited number of SCP-500, and using it to cure a case of "skull materialized inside my chest" would likely be denied, even if this were a planned experiment and not the accidental exposure event shown in your interview. The researchers definitely wouldn't be able to get authorization in under five minutes. You should try to find another way that the subject survived, though something the size of a skull interrupting the functions of your internal organs sounds pretty deadly.

You should explain why the subject in the interview is unable to remember which SCP they were working with. The interview itself is also a little nonsensical. "containment mission" should be replaced with whatever specific activity they were engaged in, and I don't really understand "thanks, you may now leave this room". It's very abrupt. The interviewer then using profanity and threatening lethal force is also confusing. In a paragraph before the interview, you should explain what was happening that resulted in the incident. A doctor killing their was into something as heavily-secured as an SCP's containment, especially if they were shouting while entering the building, is incredibly unlikely.

Instead of a such a hostile ending, you should aim for something more unsettling. I would personally have the interview conducted immediately after the skull has teleported somewhere else and the doctor (or D-Class, whichever fits the situation you decide to go with) lies dying. Maybe have them say something to try explaining the SCP's motivation. "It just wants to know where the sounds come from… it wants to try to understand us…" or something. Whatever fits the narrative and origin you have for it.

There are several guides to writing SCPs, which you can find here:

http://www.scp-wiki.net/guide-hub