Detect silence when recording

How can I detect silence when recording operation is started in Java?

Calculate the dB or RMS value for a group of sound frames and decide at what level it is considered to be ‘silence’.

What is PCM data?

Data that is in Pulse-code modulation format.

How can I calculate PCM data in Java?

I do not understand that question. But guessing it has something to do with the speech-recognition tag, I have some bad news. This might theoretically be done using the Java Speech API. But there are apparently no ‘speech to text’ implementations available for the API (only ‘text to speech’).

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I have to calculate rms for speech-recognition project. But I do not know how can I calculate in Java.

For a single channel that is represented by signal sizes in a double ranging from -1 to 1, you might use this method.

/** Computes the RMS volume of a group of signal sizes ranging from -1 to 1. */
public double volumeRMS(double[] raw) {
    double sum = 0d;
    if (raw.length==0) {
        return sum;
    } else {
        for (int ii=0; ii<raw.length; ii++) {
            sum += raw[ii];
        }
    }
    double average = sum/raw.length;

    double sumMeanSquare = 0d;
    for (int ii=0; ii<raw.length; ii++) {
        sumMeanSquare += Math.pow(raw[ii]-average,2d);
    }
    double averageMeanSquare = sumMeanSquare/raw.length;
    double rootMeanSquare = Math.sqrt(averageMeanSquare);

    return rootMeanSquare;
}

There is a byte buffer to save input values from the line, and what I should have to do with this buffer?

If using the volumeRMS(double[]) method, convert the byte values to an array of double values ranging from -1 to 1. 😉