There are probably many different solutions to this problem. One thing you don't need to do is write more software. There is plenty of great software out there that will do the job. Hiring a local audio engineer who has experience with sound design and recording will probably save you a lot of time, money, and headache.
But if you want to do it yourself, or know what to look for, here are two ideas:
- Process recordings of the actual device to get the desired sound.
- Make recordings of similar things and assemble them together so that they make the sound you want. (Foley)
It may help to use one or more shotgun microphones to record your device. You probably won't be able to perfectly isolate the sound you want this way, any more than you would be able to take a picture of a perfect sine wave in a bathtub that contains a toddler - no matter how expensive the lens you buy.
You may be able to do some filtering to remove unwanted sound - Audacity either includes all the filtering tools you need, or the separate plugin bundle does. You may also want to look into FFT audio editors such as SPEAR. This isn't easy, though. It will take time, reading, and practice to build the basic skills you need. And then more time and practice to actually extract the sound you want.
In movies, TV and commercials a process called Foley is used. Foley work is basically recording things that sound similar enough to the sound you want, and then dubbing them together to make a soundtrack. Many of the "realistic" sound effects we are used to hearing are just as fake as the 3D graphics we see. In some cases, we are so used to the fake movie sounds that the actual sounds in real life sound "fake".
You might be able to get the sound you want by baking your stuff on a cookie sheet, and then pulling the cookie sheet out and holding a microphone up against the cooling stuff. Then you overlay that sound on top of the blower sound of your machine before it starts popping. If that doesn't work, try other household goods that make the right sound. If that doesn't work, go crazy at the supermarket and hardware store buying likely items to smash when you get home.
TL;DR A Shotgun Microphone is the piece of equipment that you think you want, but equipment alone won't solve this problem.