A typical giant galaxy, such as the one you've provided a picture of, has a radius of something like $10\;\rm kpc$ (kiloparsec - $1\;\rm pc \approx 3.2\;ly$).
A supermassive black hole hosted in such a galaxy has a mass of something like $10^6-10^9\;\rm M_\odot$ (solar mass, $1\;\rm M_\odot \approx 2\times10^{30}\; kg$). The monstrous billion solar mass black holes are really only found in particularly large ellipticals; the galaxy in your photo probably hosts one of about one to a few million solar masses. The horizon radius of such a black hole will be on the order of the Schwarzschild radius, so:
$$r_s=\frac{2GM}{c^2}\approx10^{-10}\rm\; kpc$$
So the supermassive black hole is something like 100 billion times smaller in radius than the galaxy, way way WAY smaller than a pixel in a picture like the one you show.
Furthermore, there are a lot of stars in the central region of a galaxy and many will be close (or roughly in front of) the black hole, not to mention clouds of intragalactic gas that may obscure the view to the black hole.
That said, it is becoming possible using very long baseline interferometry to take "pictures" of a couple of nearby black holes. I don't think there are any successful images yet, but we'll probably get some in the next 3 years or so using the Event Horizon Telescope. A prediction of what will be seen:
The formation of the image is quite complicated (the paper I link later gives a lot of the gory detail if you're interested). First, note that this is in "false colour", the colour indicates the intensity of the radiation from blue (low) to white (high). The photons come from a disk hot gas ("accretion disk") that is expected to be found near many black holes. Those in the picture are those which happen to approach the black hole, but do not enter it. Because of the curvature of spacetime, photons can orbit the hole and accumulate in these "photon orbits". The orbits occur a few Schwarzschild radii from the hole. The orbits aren't stable, so some photons eventually plunge into the hole, while others escape away - these are the ones in the picture. The strong asymmetry in the image (while you'd expect a BH to be very symmetric) is due to the fact that the source of the light (the accretion disk) is not spherically symmetric, and only approximately axially symmetric - it may be warped, have bright and dim spots, etc. One side of the image is brighter because typically one side will be relativistically beamed toward us while the other will be beamed away. This is as close to a black hole "looking black" as we're likely to get. There are photons orbiting across the "face" of the hole in the picture, but none make it to us from that direction, so the hole appears black in the image.
One paper I particularly enjoyed reading about the more theoretical aspects of these black hole images: Testing the no-hair theorem with event horizon telescope observations of Sagittarius A*. It includes more simulated images at resolutions more like what we'll realistically achieve with the EHT.
Warp drives are not allowed by the basic laws of physics, in particular the theory of relativity prohibits any superluminal motion or superluminal propagation of usable information. So whatever "exotic matter" or other wordings are proposed to justify the superluminal warp drives is banned, too. The typical "exotic matter" needed for warp drives would need to admit a negative energy-mass density. If Nature allowed the energy density to go negative, the vacuum itself would be unstable.
The laws of physics also ban the transfer of an object from a universe to a different universe through a black hole, whether it is primordial or not. Wormholes allowed by the laws of physics, if there are any, have to be non-traversable. It means that by jumping into such a black hole, he is guaranteed to end up in the singularity. At most, the singularity where he ends may be shared between a pair (or perhaps a higher number) of black holes. Such a pair of black holes is known as the non-traversable wormhole or the Einstein-Rosen bridge (at least the simplest one). But whoever falls into a black hole can never escape to the "liberated space" outside it, in any Universe, by the very definition of a black hole. Incidentally, the technical reason why a traversable wormhole can't be built is the very same why the warp drives are impossible: negative energy density would be needed for them, too.
Sagittarius A* is in no way the nearest black hole to the Earth. For example, V404 Cygni has a black hole in it that
https://en.wikipedia.org/wiki/V404_Cygni
is 7,800 light years away, and there are probably many closer ones, too.
It wasn't my plan to correct statements in the question but I have to. While an idealized empty large black hole is indeed mildly curved and one may survive the fall behind the horizon, that's not true for realistic black holes, especially Sagittarius A*. The latter is surrounded by plasma, matter that the black hole devours. A good description of the plasma around Sgr A* is the two-temperature plasma. The temperature of the electron component of the plasma is about 100 billion kelvins. No material that could be used to build a spaceship could survive these conditions. We would need a much more isolated black hole to avoid this thermal hell but it isn't clear whether such astrophysical black holes exist.
Best Answer
I'm not going to address the production mechanism,1 just the nature of the "sound" in this case.
What you think of as the hard vacuum of outer space could just as well be seen as a very, very, very diffuse, somewhat ionized gas. That gas can support sound waves as long as the wavelength is considerably longer than the mean free path of the atoms on the gas.
As for the tone, there is a simple relationship between the tone of the same name in different octaves, so once they know the dominant frequency they can figure its place on the scale.
1 Though it won't be happening inside the event horizon -- which is where "not even light can escape" holds -- but in the region around the hole proper where it accumulates gas and dust and the magnetic fields from the hole play merry havoc with the ionized components of the accumulated stuff.