A simplified prediction model for the early-to-late energy ratio has been tested for small rooms that are typically used in video conferences. The prediction model is a modified diffuse-field model, using Barren's revised formula for a distance-dependent reverberation level, together with Vorlander's revised formula for a constant reverberation level. Measurements have been carried out in a few rooms and early- and total-energy levels have been compared with predictions according to the simplified model and predicted octave-band levels are typically within 1 dB of measured values, for the frequency range of 250 Hz to 2 kHz. Measured impulse responses were then convolved to simulate a video conference setup and simplified predictions of the early-to-late energy ratios, C50, for convolved impulse responses gave prediction errors that were on average around 1.5 dB as compared with (convolved) measurements.
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