[magicalhippo]

> it really doesn't matter much what the original frequency range of a signal is

It does matter. The waves they measure have so low frequency they've barely measured a single period of it. The higher frequency waves are lost in the noise.

So what should they play? A single 1kHz note is pretty uninteresting.

[smallnamespace]

I agree that's one way to look at it. I prefer the framing that the signal just isn't that interesting to listen to.

Compare to the cosmic microwave background - we have no problem converting microwaves to visible light (implicitly doing a frequency shift), but the picture you see doesn't vary despite us having had enough time to collect many cycles of data.

The gravitational background should be similar - even if we collected data for thousands of years we're not going to hear a cool 'bloop' like for black hole mergers because interesting transients just aren't in the signal.