I was testing my new harmonizer network (with my mic open) and a new SMS arrive to my phone…
)
funny, don’t? a perfect pulse…
btw: any of you could give a complete explanation about this kind of effect? I also noticed the same with some speakers (of course only hearing the signal) and I think a big clue are the wires, because with my car speakers that effect only happen when I have plugged my “cassette-to-mini-plug” adaptor…
Update: check “SMS interference mystery solved” post.
English 
Español 
I’ve found nice data in wikipedia[1].
It seems to be radiofrequency interference produced by the the phone, and filtered by the mic-cable-probes-osciloscope system. I think there is only a square pulse because the carrier frequency is much higher than filter cutoff frequency (maybe near 10^5 times).
[1] http://en.wikipedia.org/wiki/GSM#Radio_interface
Pingback: SMS interference mystery solved | AudioResearchBlog