What is the meaning of this broadcast?

In Batman: Arkham City, you can use the Cryptographic Sequencer to decode various broadcasts.

At the approximate position of 637 on the x-axis, and 472 on the y-axis is a person reading off a series of numbers, similar to a number station. When you try to decode the broadcast on the sequencer, it doesn't do anything.

Has anyone discovered what these numbers mean? The number sequence is (hopefully I wrote it down right):

9-23-9-12-12-18-5-20-21-18-14-2-1-20-13-1-14

Solution 1:

It's a substitution cipher. a = 1, b = 2, etc.

iwillreturnbatman

or

I will return Batman

I just listened to it, and the voice is familiar, put I can't put it to a character (not the Riddler, he wants you to know the puzzle is his).

Solution 2:

It's a substitution cipher: A=1, B=2, ..., Z=26.

Decoded, it reads (station 675-525):

I WILL RETURN BATMAN

There are also two other messages that you do no get until later in the game. One of them is (station 500-900):

5 15 9 7 21 18 18 14 3 5 24 15 12 7 22 3 10 5 15 9 22 3 8 25 26 15 16 25 10 15 17 25

This one is still a mono-alphabetic substitution cipher, but with a slightly different code: A=3, B=2, C=1, D=26, E=25, ..., Y=5, Z=4.

When finally decoded, it reads

YOU WILL PAY FOR WHAT YOU HAVE DONE TO ME

The last one is (station 200-500 - you have to beat the game first??)

3 20 26 18 26 16 24 1 11 4 24 9 3 8 5 2 12 18 6 16 7 11 3 10 17 5 13 4 21 8

Unfortunately, this one doesn't seem to be a mono-alphabetic substitution cipher - no matter what substitutions we use, we get gibberish:

CTZRZPXAKDXICHEBLRFPGKCJQEMDUH

There are rumors circulating (originating, it appears, with IGN) that when decoded, this reads "I am your darkest nightmare dark knight. Gotham city waits for his savior." However, this is clearly wrong - there are way too many letters!

Fortunately, not too long ago one of the super-sleuths on Batman: Arkham City forums decoded it:

If you treat it as a Vigenère cipher using the key SCARECROW, then do atbash, the message comes out to:
FEAR WILL TEAR GOTHAM CITY TO SHREDS
Therefore, it is pretty obvious the messages are being sent by Scarecrow.

Solution 3:

It's a pretty simple code. Think 1=A, 2=B, etc.