Mcu32
Senior Member

Oh.. not a good Idea. Never use a really slow protocol like I2C in a ISR. This will always slow down your program exactly when you don't want it to. Don't do it like that. Edit: If you read the time via i2c...

Here's an article about self-noise : http://openaudio.blogspot.com/2017/03/teensy-audio-board-self-noise.html

YOu can get almost any frequency by modifying the PLL settings (and by probably not using the analog* functions)

Well, the shield is not as bad as your plot shows. There is something wrong. But you simply can't judge that from a song. Do you use the linear input? (not mic) The user blackadr made a quite good board. I've used...

Also, keep in mind that the shield is consumer quality. But it's quite ok.

?? Any song you record is not white noise. Not sure what you're trying to say. A recorded song will *never* show a linear spectrum. Distortions may caused by too high input level?

If you search the forum, you can find audio-shield spectrum plots.

Your song is probably not very similar to https://en.wikipedia.org/wiki/White_noise :) Only in this case you would see a more linear spectrum.