European Power Line Mains Real Time Frequency Data

[Craig Maier]

Here is an interesting link that provides real time frequency data for their power line mains. These types of data can be useful in recording authentication since power line "hum" is invariably recorded incidentally on forensics recordings. That hum can be tracked and logged with the Diamond Cut Forensics10 Frequency Tracker. Here is the website that shows the Euro mains frequency:

http://www.mainsfrequency.com/

Craig

[ebrjvd]

I use the recorded hum as a means to correct playback speed.
It would be useful to have a tool that autocorrects speed based on hum. Could also be used to correct wow.

One cassette we had to digitise had both 50 and 60 Hz hum, so probably a copy of a recording made in another part of the world...

Cheers,
Jos

[Craig Maier]

Wow is defined as having delta f / F components up to 6 Hz, so it is theoretically possible to wrap a control loop around the hum to compensate for wow. However, I suspect that the control loop would be tricky to stabilize because the audio signal is "in-band" with the reference signal. Clearly, it could never correct flutter (because of the Nyquist criterion).

Craig