Red line at 40 Hz

[Udo]

Hello,
when I use the spectogram it seems to work as expected. When I am in meditation mode I can see a red area on the left side (8 Hz) and a green/gray/blue area on the right side (> 8 Hz). But there is always a permanent thin red line at 40 Hz. Can anybody has an idea, what this means. Is this really brain waves or rather a disturbing frequency. And when it is rather the second, what could that be?

Best regards
Udo

[James]

It's probably not 40Hz, but 50Hz from a nearby mains power source. Try outside and I'm sure you'll see it go away.