On Mon, Dec 13, 2010 at 8:26 PM, Patrick Noffke <[email protected]>wrote:
> > On Sat, Dec 11, 2010 at 1:15 PM, TheSeeker <[email protected]>wrote: > >> I have been thinking if when i use the funcion AudioRecord at 8KHz by >> sample I have aliasing? To avoid the effect of aliasing normally i >> should put a low pass filter to eliminate frecuencies above 4KHz >> So i have this filter for default? >> >> > You can't remove aliasing after it's occurred, so if there isn't an analog > anti-aliasing filter prior to sampling, you cannot remove it in the digital > domain. I would expect the A/D to operate as a sample-and-hold, which would > alias frequencies higher than f_s/2. The other option that could be > implemented is to integrate the signal during the sample period, which has > some low-pass filtering effect (boxcar filter), but it's not a very good > filter. > > I'm not aware how the electronics work in the devices. What device(s) are > you using? Maybe the 8kHz sampling is actually sampled at 44.1 kHz, and > there is digital filtering/down-sampling to 8kHz. Or perhaps there are > electronics that change the anti-aliasing filter as the sample rate changes. > > The other question is why are you sampling at 8kHz? Will you likely have > frequencies above 4kHz? > > Patrick > > -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected]<android-developers%[email protected]> > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en > -- Julie http://www.sirsainfo.in/ <http://t> http://tradinglogically.blogspot.com <http://tradinglogically.blogspot.com> http://vikitionary.blogspot.com http://gandhi-the-man-of-millenium.blogspot.com/ -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
