I'll have a hunt for some appropriate samples. I have to do some back-end tweaks before I can add more sounds, though, because there's a practical limit to how many samples the browser can stream at once.
Thanks very much for your suggestion!
To add similar services I've been using for quite a while:
http://www.noisli.com/ (very nice UI with changing background colour, a distration free editor and so on)
http://mynoise.net/NoiseMachines/ (quite professional)
For the life of me, though, I haven't been able to remember the name the last couple time's I've wanted it (and my bookmarks are horrendously disorganized at the moment), and googling different iterations of "white noise generator sliders people birds rain" didn't yield success. I need to stash this away somewhere I won't lose it...
I have actually wondered about the name thing. It is a little whimsical, and I guess it would be easy to mix up with lots of similar descriptions like "a quiet buzz" or "a gentle burble". From that perspective, it might have been better to choose something more memorable.
The site won't rank well in google for descriptive terms because it doesn't contain a lot of text. Even for terms it does contain, it doesn't do very well (e.g. it ranks at ~20 for "ambient noise" in google US). I haven't worried about that so far because the large majority of the traffic is direct, social or for the exact term "a soft murmur".
Based on your other comments it seems like you really know what you're doing in these spaces. I'm no expert, but based on all the positive feedback, capturing organic search traffic could help you kill it. Show them and they'll stick.
And the luck/chance involved :) basically, the votes a new link gets in first 30mins largely decides whether it will make to front page or not. More specifically, the first upvote because then social proof kicks in (hey it must be good if someone liked it).
So while posting to HN/Reddit might help to kick in, I would take it more as 'good if it hits, fine if it doesn't'.
Thanks again!
Another key thing is to understand the community. There is radical cultural diversity between subreddits which manifests in very different reactions to self-promotion. It's essential to engage appropriately and respectfully.
Something I've used for other projects is searching for coverage of competitors in the same space, then pitching to people who have already featured them. Again, very important to hand-tailor each pitch and offer value to the person you're contacting.