This is an odd one. On the one hand you have agents and editors who say that no response means no. On the other there are editors who won't even look at a manuscript until they have been chased the first time. To complicate matters, there are other editors who will dump a manuscript unless you do chase them.
This is the bit where you need an agent who knows what the particular publishing house's rules are, and also when they break them. For example, I had an agent who said that no response in three months means no and then sent me a rejection eight months later.
Without an agent (not for lack of trying) I'm a little lost, but with the end of the four weeks coming up on Friday I need to make a decision. The choice is surprisingly easy, although it might be my professional background talking: if I hear nothing by then, then either by email or phone I'll be asking politely about feedback on Monday.
Since acceptances are usually fast responses, I do suspect this is a no.