On Fri, 20 Feb 2004, matt wrote: > I would have thought that should have been gotten rid of... > > Notch filter would only get rid of the fundamental frequency unless you > notch at the harmonics also. > > Best bet I would say is a high pass filter at say 500hz. > > Reasonably simple to make with a resistor and capacitor... I think Sound > On Sound magazine (which has archives on the web) had an article on how > to build one... > > The thing is, most of the codecs available in * should be high and low > pass filtering it anyway...
My first thought was an RC filter, too. But I'd suggest that 500 Hz is too high a cutoff, because a note like a middle C is 256 Hz. I don't think it's uncommon for a voice (especially a male voice) to be in that range frequently. Although (in English, at least) vowels generally have a low frequency and sharp consonants (like a t) have a high frequency. It's the consonants which do the most for understanding a word, so maybe having those low frequencies attenuated wouldn't be so bad after all. But as somebody else pointed out, a first-order RC filter probably wouldn't attenuate quickly enough. By the time you get into a multi-order filter, it's probably best to be doing it in software (since the signal is going to be digitized anyway). Greg > > Matt > > Michael Welter wrote: > > > I live at 8000' in the Rockies. We have lots of woodpeckers--they > > especially love to drill 4" holes in the north side of my house. > > > > They also like to drill on the arial telephone cables. Water then > > gets into the cable and causes a partial grounding on the circuits. > > This causes 60Hz hum to be heard on the line as well as a loss of > > amplitude. Qwest says tough s--t. > > > > All three of my POTS lines have hum. They are connected to an Adtran > > 750 and my asterisk system (a testbench for commercial endeavors.) > > > > The hum has always been bad on my end. Since I installed *, several > > of my callers have remarked about the hum. > > > > So here's the question: Could a notch filter of sorts be installed in > > the codecs I use? Filter-out everything between, say, 55 and 65Hz? > > > > Alternatively, is there a feature on the Adtran FXO card that deals > > with this? > > > > Thanks for your help, > > Mike > > > > > > > > _______________________________________________ > > Asterisk-Users mailing list > > [EMAIL PROTECTED] > > http://lists.digium.com/mailman/listinfo/asterisk-users > > To UNSUBSCRIBE or update options visit: > > http://lists.digium.com/mailman/listinfo/asterisk-users > > > > > _______________________________________________ > Asterisk-Users mailing list > [EMAIL PROTECTED] > http://lists.digium.com/mailman/listinfo/asterisk-users > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users > _______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
