LoudNoiseDetector.java

/*
 * Copyright 2012 Greg Milette and Adam Stroud
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * 		http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package root.gast.audio.interp;

import root.gast.audio.record.AudioClipListener;
import android.util.Log;

/**
 * @author Greg Milette <<a
 *         href="mailto:gregorym@gmail.com">gregorym@gmail.com</a>>
 * 
 */
public class LoudNoiseDetector implements AudioClipListener
{
    private static final String TAG = "LoudNoiseDetector";

    private double volumeThreshold;

    public static final int DEFAULT_LOUDNESS_THRESHOLD = 2000;

    private static final boolean DEBUG = true;

    public LoudNoiseDetector()
    {
        volumeThreshold = DEFAULT_LOUDNESS_THRESHOLD;
    }

    public LoudNoiseDetector(double volumeThreshold)
    {
        this.volumeThreshold = volumeThreshold;
    }

    @Override
    public boolean heard(short[] data, int sampleRate)
    {
        boolean heard = false;
        // use rms to take the entire audio signal into account
        // and discount any one single high amplitude
        double currentVolume = rootMeanSquared(data);
        if (DEBUG)
        {
            Log.d(TAG, "current: " + currentVolume + " threshold: "
                    + volumeThreshold);
        }

        if (currentVolume > volumeThreshold)
        {
            Log.d(TAG, "heard");
            heard = true;
        }

        return heard;
    }

    private double rootMeanSquared(short[] nums)
    {
        double ms = 0;
        for (int i = 0; i < nums.length; i++)
        {
            ms += nums[i] * nums[i];
        }
        ms /= nums.length;
        return Math.sqrt(ms);
    }
}