I am a journalist and recorded a conversation in a noisy cafe. Basically I can't hear the conversation and want to know if it is possible to try and improve the conversation. I use Audacity. I've tried tutorials on "removing background noise" but that's more for subtle background noises. The cafe was pretty loud! Lesson learned. Thank you.
As everyone else has said, noise reduction is the way to go, pretty aggressive noise reduction is all that will help I think. Thing is, if you want this conversation for sound bites or anything, it's probably going to be unusable. You may be able to pull enough of the noise out so that the vocals become just audible, but they're likely to sound watery and like a bad quality MP3. Might work for transcription purposes but that's about it.
I'd suggest getting a mic with a lot of off axis rejection if you need to record in such an environment again. Or have those involved in the conversation ware clip-on mics.
This is definitely a situation where an ounce of prevention is worth a pound of cure.
You can dramatically reduce the amount of background noise with Audacity's Noise Removal tool.
Highlight a section of the audio clip when the background noise is loudest and no one is speaking. Then go to Effect > Noise Removal.
With the various parameters provided by the Noise Removal tool, it will probably take a few tries before you get it just right. You can then normalize the entire clip (after noise reduction) to make the vocals louder.
Izotope RX, is the way to go. There are options for all budgets; 'RX Elements ','RX Standard', and RX advanced.
I'm an Izotope RX standard owner, its any invaluable tool for post audio. You can download 30 days trial with a demo mode - it will give you an idea of its capability. Would definitely recommend you to try.