Incorrect display of peak frequencies about audio-analyzer-for-android HOT 1 OPEN

Hi!

Thank you for using my app.

I would guess that these artifacts are due to the emulator, not the app itself.

For screenshot-1.

I can see two noise floors. The higher one (around -54dB) should relate to the noise in the mic, the lower one (around -120dB) should relate to the anti-aliasing filter which limit the signal to 4kHz, and that means, maybe somewhere in the audio processing pathway, 8kHz sampling rate is assumed.

Your experiment further verified the existence of this 4kHz low-pass filter, because when input frequency is higher than 4kHz, the peak frequency no longer matches.

For screenshot-2, screenshot-3, screenshot-4.
The -120dB floor disappeared, which is weird, if the audio processing method didn't change and no automatic gain control applied, then it indicate recorder buffer overrun, which will leads to discontinuous samples and the slow-decaying spectrum.

Another possibility is, although not so sure about this, clipping in the input signal, so reduce the volume (hardware or software) may help.

I would suggest first turn on the "overrun warning" in the app preference, see if there is overrun. Also reduce input signal amplitude or volume.

I also tried it in the emulator (along with the Android Studio, in Linux), everything looks good. But I remember that in the old day (e.g. 4 years earlier), the running speed of the emulator is not fast enough so that there is constantly buffer overrun.

I notice that you are using "Lollipop" image, and Lollipop is released in November 2014. Consider update it and see if it works.

from audio-analyzer-for-android.