The acoustic behavior of small rooms in the modal frequency band can be characterized by the modal decay times MT60. The paper explores a method for computing modal decay times from measurements of Room Impulse Responses (RIR) based on the wavelet transform. Once the resonance frequencies have been selected, the procedure computes a series of wavelet transforms of the Morlet type with decreasing bandwidth, exploiting the property that Morlet wavelets preserve the time history of energy decay. Then decay times can be calculated either by linear regression of the non-noisy portion of the curve or by nonlinear fitting of a model of decay plus noise. Examples of application of the method to real RIR measurements are shown.
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