Decibel Averaging in Reverberant Power Measurements Free

The measurement of sound power in a reverberant room makes use of the level corresponding to room‐averaged sound intensity, 10 log 〈I〉. But when measurements are in decibels—as is usually the case—it is computationally simpler to employ the room‐averaged level 〈10 log I〉. This substitution leads to a bias in the direction of underestimating the true power. In many practical situations, the bias can be estimated theoretically and added as a correction term to the simple average level. For pure‐tone excitation, the bias term is largest, amounting to 2.5 dB. For noise excitation, the bias decreases with the product of noise bandwidth B and reverberation time T. When BT>30, bias is less than 0.5 dB. When BT>130, bias is less than 0.1 dB; and decibel averages may be substituted for intensity averages with impunity.