dtczhl / dtc-acoustic-spectrumer

display spectrum of ambient sounds

dtc-acoustic-spectrumer

 

A simple android app to display the spectrum of received sounds

Screenshot

Screenshot from Huawei Mate 20. You can see that there is a spike around 19 KHz when I send sounds of that frequency. See my dtc-frequency-player about how to send sounds of a specific frequency.

Ranges:

• x-axis (horizontal): [0Hz, 24 KHz]
• y-axis (vertical): strength of frequency in dB

Source Code

The interface to the spectrum analysis is the AnalyzeFrequency.java class. The spectrum range is [0 Hz, 24 KHz].

1. start frequency analysis

  AnalyzeFrequency mFftAnalysis = new AnalyzeFrequency(mHandler, mRun);
  mFftAnalysis.start();

  //  FFT magnitude for current frame of received sound.
  //  Default length: 4096/2-1
  mFftAnalysis.mMagnitude

2. stop frequency analysis

  if (mFftAnalysis != null) {
      mFftAnalysis.stop();
      mFftAnalysis = null;
  }

Some critical steps to create this Android app from scratch.

1. download the source code of Apache Commons Math library for Java that includes Fast-Fourier-Transform (FFT). http://commons.apache.org/proper/commons-math/download_math.cgi

2. extract the downloaded file. Goes to commons-math3-***/src/main/java/org/apache/commons/math3, remove the geometry folder which is not compatible with Android.

3. goes to commons-math3-***/src/main/java/ and copy the org folder to your Android project app/src/main/

4. enable Android permission <uses-permission android:name="android.permission.RECORD_AUDIO" />

Phones Tested

• Huawei Mate 20
• Google Pixel 2