[smallnamespace]

Yes but for those motivated to hear the low-frequency waves, adding a frequency shift to the end of the signal processing pipeline would've been trivial.

Since the incremental effort is so low, it really doesn't matter much what the original frequency range of a signal is.

[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.