float powerOfLastPeriod;
		short* signal = (short*)result;
		float powerSum = 0.0f;
		for (int i = 0; i < m_PeriodSizeInSamples; ++i) {
			float amp = (float) abs(signal[i]);
			powerSum += amp * amp;
		}
		powerOfLastPeriod = powerSum / (32768.0f * 3.27680f * (float) m_PeriodSizeInSamples);

		if(powerOfLastPeriod < 1.) {
                         ......
                }