CODEWITHSUNDEEP
javaandroidfftmicrophone
user2610470
user2610470

Reputation: 13

Android fft get higher frequency range

I'm using the code over at https://github.com/sommukhopadhyay/FFTBasedSpectrumAnalyzer. The problem i'm running into is the spectrum graph only shows low ranges.

How can I modify the code so that I can see a more complete frequency range?

int frequency = 8000;
int channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO;
int audioEncoding = AudioFormat.ENCODING_PCM_16BIT;

private class RecordAudio extends AsyncTask<Void, double[], Void> {
    @Override
    protected Void doInBackground(Void... params) {

        int bufferSize = AudioRecord.getMinBufferSize(frequency,
                channelConfiguration, audioEncoding);
        AudioRecord audioRecord = new AudioRecord(
                MediaRecorder.AudioSource.DEFAULT, frequency,
                channelConfiguration, audioEncoding, bufferSize);

        short[] buffer = new short[blockSize];
        double[] toTransform = new double[blockSize];
        try{
            audioRecord.startRecording();
        }
        catch(IllegalStateException e){

        }
        while (started) {
            int bufferReadResult = audioRecord.read(buffer, 0, blockSize);

            for (int i = 0; i < blockSize && i < bufferReadResult; i++) {
                toTransform[i] = (double) buffer[i] / 32768.0; // signed 16 bit
            }

            transformer.ft(toTransform);
            publishProgress(toTransform);
        }
        try{
            audioRecord.stop();
        }
        catch(IllegalStateException e){

        }

        return null;
    }
}

Upvotes: 0

Views: 697

Answers (1)

Paul R
Paul R

Reputation: 212929

If your sample rate is 8 kHz then you will only be able to see frequencies from 0 to 4 kHz. For a greater frequency range you need to increase the sample rate, e.g. if you set it to 44.1 kHz then you will see frequencies from 0 to 22.05 kHz. I'm not sure what sample rates are supported on Android with your particular device, but try changing:

int frequency = 8000;

to:

int frequency = 44100;

Upvotes: 3

Related Questions