That's quite shocking, especially that even the cheapest of ADC/DAC chips support the whole of (human)audio spectrum. Bad engineering.
All you have to do is to have calibrating stage in your app and embed some audio samples on your website to assist that process. On 16 April 2012 15:03, RLScott <fixthatpi...@yahoo.com> wrote: > If your application records audio at a specified sample rate, be aware > that some OEMs are faking it! We have a piano tuning app that needs > to detect frequencies up to about 4200 Hz. This requires sampling > audio at least twice that frequency, or 8400. So we used one of the > "standard" audio sample rates of 22050. Most devices we have tested > work fine. But on the Acer Iconia tablet something strange happens. > The calls to set up the AudioRecord at 22050 samples per second work > without error, and the frequency spectrum shows that it is indeed > returning 22050 samples for every second of audio. But then we > started looking at the higher frequencies and found a frequency fold- > back point of 3690 Hz, just as if the sample rate were really 7380 > Hz. Our conclusion is that 7380 is the native audio record sample > rate for the Acer Iconia, but other sample rates are simulated by up- > sampling. That is, certain samples are repeated in order to make 7380 > samples do the job of 22050 samples. This creates the fold-back > phenomenon where any frequency above 3690 shows up as a frequency > below 3690 by the same amount. Other than running tests on real sound > I know of no way to programmatically verify that the requested sample > rate is being honored for real and not simulated by up-sampling. (By > contrast the original Motorola Droid has not such fold-back behavior > and appears to return 22050 samples per second for real.) > > -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to android-developers@googlegroups.com > To unsubscribe from this group, send email to > android-developers+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en -- Daniel Drozdzewski -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
