You can buy a pack of 25 of them on Amazon for like $30 - https://www.amazon.com/Zapps-Orleans-Kettle-Style-Potato-Voodoo/dp/B01LY46L19/ref=sr_1_3?crid=15UW1RRP2KFWS&keywords=zapps%2Bchips&qid=1558142364&s=gateway&sprefix=zapps%2Bc%2Caps%2C123&sr=8-3&th=1
Anyone can join PenFed. I haven’t, yet, but am considering when I need a car loan.
Downside is no nearby branches but ATMs are at Safeway/Target/CVS/Walgreens and a few other chains.
I’d also recommend Charles Schwab for checking and investing. They refund all ATM fees. They have low fees on a lot of investments. They also have the downside of not having regular branches but I’ve rarely needed one. There’s offices not too far away (Bethesda, Potomac) if you really need one.
Do you pick it up on a spectrum analyzer, I would recommend you download one onto your phone [1].Do a control test in a place where you can't hear the sound, then do another where you can. Subtract the two waveforms (or just eyeball differences via pics), look at the far right and see where the frequency is peaking. This will help a lot as you can determine what might be producing the sound i.e. if I hear a sound at 50Hz and its intermittent it's probably a motor. The db level can also help you pinpoint the exact location if you measure it from different spots using [2].
[1] https://play.google.com/store/apps/details?id=org.intoorbit.spectrum&hl=en_US
[2] http://hyperphysics.phy-astr.gsu.edu/hbase/Acoustic/isprob2.html