http://stackoverflow.com/questions/2413426/playing-an-arbitrary-tone-with-android Corrected ramping

gistfile1.java

void genTone(){
    // fill out the array
    for (int i = 0; i < numSamples; ++i) {
        // sample[i] = Math.sin(2 * Math.PI * i / (sampleRate/freqOfTone));
        sample[i] = Math.sin((2 * Math.PI - .001) * i / (sampleRate/freqOfTone));
    }

    // convert to 16 bit pcm sound array
    // assumes the sample buffer is normalised.
    int idx = 0;
    int ramp = numSamples / 20;

    for (int i = 0; i < ramp; i++) {
        // scale to maximum amplitude
        final short val = (short) ((sample[i] * 32767) * i / ramp);
        // in 16 bit wav PCM, first byte is the low order byte
        generatedSnd[idx++] = (byte) (val & 0x00ff);
        generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
    }

    for (int i = ramp; i < numSamples - ramp; i++) {
        // scale to maximum amplitude
        final short val = (short) ((sample[i] * 32767));
        // in 16 bit wav PCM, first byte is the low order byte
        generatedSnd[idx++] = (byte) (val & 0x00ff);
        generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
    }

    for (int i = numSamples - ramp; i < numSamples; i++) {
        // scale to maximum amplitude
        final short val = (short) ((sample[i] * 32767) * (numSamples - i) / ramp);
        // in 16 bit wav PCM, first byte is the low order byte
        generatedSnd[idx++] = (byte) (val & 0x00ff);
        generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
    }
}