I recorded a market research interview using ACR recorder on my andriod. I can hardly hear the person on other side when I play the recording. Tried amplifying through Audacity, using compressor settings and even noise reduction but nothing worked. Is there any other solution? Please help
You amplified and compressed but "nothing worked". What does that mean? I would think that not working means it doesn't increase the volume. But you say it increases the noise with the voice, which means it's working exactly how it's supposed to.
When you compress, you are reducing the amplitude of the signal above the threshold by the ratio. So, if you are putting the threshold at -80dB as you say, you would be smashing everything starting at that level (which would include the noise), then when you boost all of that, you are increasing the noise (which is now much closer in level to the voice). You need to try increasing your threshold quite a bit. It might be better to not compress at all, and just boost the whole thing.
You can also try EQ, especially with a high-pass filter. Without the wav, it's hard to give suggestions.