4. A method for determining speech level, said method including steps of: (a) performing voice detection on an audio signal to identify at least one voice segment of the audio signal, and for each said voice segment, generating frequency domain audio data indicative of the voice segment and determining a parametric spectral model of content of the voice segment from the frequency domain audio data, where the frequency domain audio data are organized in a set of frequency bands, the spectral model determines a distribution of speech level values for each frequency band of the set, and the spectral model determines an estimated speech level for said each frequency band of the set; (b) for each said voice segment, generating data indicative of corrected estimated speech levels, including by using correction values determined from a predetermined reference speech model to correct the estimated speech levels for the frequency bands of the set, where the reference speech model determines a reference speech level value distribution for each frequency band of a set of frequency bands of frequency domain audio data indicative of reference speech, and each of the correction values is determined from the reference speech level value distribution for a different one of the frequency bands; and (c) generating a speech level signal in response to the data indicative of corrected estimated speech levels for each said voice segment, wherein the speech level signal is indicative, for each said voice segment, of a level of speech indicated by the voice segment.
4. A method for determining speech level, said method including steps of: (a) performing voice detection on an audio signal to identify at least one voice segment of the audio signal, and for each said voice segment, generating frequency domain audio data indicative of the voice segment and determining a parametric spectral model of content of the voice segment from the frequency domain audio data, where the frequency domain audio data are organized in a set of frequency bands, the spectral model determines a distribution of speech level values for each frequency band of the set, and the spectral model determines an estimated speech level for said each frequency band of the set; (b) for each said voice segment, generating data indicative of corrected estimated speech levels, including by using correction values determined from a predetermined reference speech model to correct the estimated speech levels for the frequency bands of the set, where the reference speech model determines a reference speech level value distribution for each frequency band of a set of frequency bands of frequency domain audio data indicative of reference speech, and each of the correction values is determined from the reference speech level value distribution for a different one of the frequency bands; and (c) generating a speech level signal in response to the data indicative of corrected estimated speech levels for each said voice segment, wherein the speech level signal is indicative, for each said voice segment, of a level of speech indicated by the voice segment. 6. The method of claim 4 , wherein the parametric spectral model is a Gaussian parametric spectral model, and the estimated speech level for each frequency band of the speech signal is an estimated mean speech level.