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copied!<p>I appreciate Han's post, and wrote a routine that can calculate decibels on 8 and 16 bit audio formats, with multiple channels using his example.</p> <pre><code>public double MeasureDecibels(byte[] samples, int length, int bitsPerSample, int numChannels, params int[] channelsToMeasure) { if (samples == null || length == 0 || samples.Length == 0) { throw new ArgumentException("Missing samples to measure."); } //check bits are 8 or 16. if (bitsPerSample != 8 && bitsPerSample != 16) { throw new ArgumentException("Only 8 and 16 bit samples allowed."); } //check channels are valid if (channelsToMeasure == null || channelsToMeasure.Length == 0) { throw new ArgumentException("Must have target channels."); } //check each channel is in proper range. foreach (int channel in channelsToMeasure) { if (channel < 0 || channel >= numChannels) { throw new ArgumentException("Invalid channel requested."); } } //ensure we have only full blocks. A half a block isn't considered valid. int sampleSizeInBytes = bitsPerSample / 8; int blockSizeInBytes = sampleSizeInBytes * numChannels; if (length % blockSizeInBytes != 0) { throw new ArgumentException("Non-integral number of bytes passed for given audio format."); } double sum = 0; for (var i = 0; i < length; i = i + blockSizeInBytes) { double sumOfChannels = 0; for (int j = 0; j < channelsToMeasure.Length; j++) { int channelOffset = channelsToMeasure[j] * sampleSizeInBytes; int channelIndex = i + channelOffset; if (bitsPerSample == 8) { sumOfChannels = (127 - samples[channelIndex]) / byte.MaxValue; } else { double sampleValue = BitConverter.ToInt16(samples, channelIndex); sumOfChannels += (sampleValue / short.MaxValue); } } double averageOfChannels = sumOfChannels / channelsToMeasure.Length; sum += (averageOfChannels * averageOfChannels); } int numberSamples = length / blockSizeInBytes; double rootMeanSquared = Math.Sqrt(sum / numberSamples); if (rootMeanSquared == 0) { return 0; } else { double logvalue = Math.Log10(rootMeanSquared); double decibel = 20 * logvalue; return decibel; } } </code></pre>

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