The Sounds of Silence
If you want to reduce background noise in your recording here are some suggestions. Increasing the gain will just mean that the difference between your voice and the noise should be greater, so less need to increase the gain later which also increases the noise volume. The noise is from the internal circuitry of the mic / recorder, (or mic cable) and that is usually because of insufficient shielding from external radio frequency interference (RFI) which create noise in the internal circuitry. These may not be possible to avoid in cities, as the neighbours' wifi and other radio sources will be present. Recordings far from cities have much less of that background noise because it is further away from all that RFI. The microphone cable can be a source of noise, so to check this you can try recording direct onto the recorder using the internal mics. You can also put an RF reduction device onto the cable.
Audacity is a free program which can help with noise reduction. If the noise is regular you take a sample of it then the noise reduction removes this from the rest of the recording. You can also use a high pass filter to get rid of low frequency noise or a low pass filter to remove high frequency noise.
Let me know your other ideas and I will include them here.
