no waveform appears in audacity to represent it.
If you’re using the regular blue waves, they only show the loudest 25dB or 30dB of sound out of 90dB or so total. You can hear quiet stuff and not have blue waves. That’s where your environment noises are coming from.
It’s not the best idea to reduce recording volume to try and get rid of the motorbikes. That also makes your voice noisy (fffffffff).
You should do whatever you can to not record the motorbikes. People record at night. I can record OK in my garage, but I can’t do it during the day because of my noisy street.
You can also make a “studio” out of moving blankets and plastic pipes.
Here’s a guy that can make a bathroom sound pretty good with just a blanket.
Record with your microphone at oblique placement (B) instead of straight-on, and get closer.
People have recorded voice work very successfully in their car. One of the production people at work routinely turned up with terrific voice clips and I know he lives in a very noise house. I asked him how he did it and he said “My Toyota.”
I know it seems like you should be able to push a few buttons and get rid of background noise, but it doesn’t work like that. Even with good Noise Gate settings (Effect > Noise Gate), you’re still going to have motorbikes inside your words. That and most of the solutions have problems of their own like cutting beginning and endings of words and sound pumping.
If you ever decide to read for audiobooks, ACX is looking for damage like that and they will reject you.
Koz