Microphone unit comprising integrated speech analysis

Abstract

A microphone unit has a transducer, for generating an electrical audio signal from a received acoustic signal; a speech coder, for obtaining compressed speech data from the audio signal; and a digital output, for supplying digital signals representing said compressed speech data. The speech coder may be a lossy speech coder, and may contain a bank of filters with centre frequencies that are non-uniformly spaced, for example mel frequencies.

1 .- 27 . (canceled) 
     
     
         28 . A microphone unit, comprising:
 a transducer, for generating an audio signal;   a speech feature extraction block, for obtaining speech feature values from the audio signal; and   a digital output, for supplying digital signals representing said speech feature values.   
     
     
         29 . A microphone unit as claimed in  claim 28 , wherein the speech feature extraction block comprises means for obtaining speech feature values from the audio signal by means of a filter bank for providing estimates of the signal energy in each of a set of non-equally-spaced frequency bands. 
     
     
         30 . A microphone unit as claimed in  claim 29 , wherein the non-equally-spaced frequency bands are mel frequencies. 
     
     
         31 . A microphone unit as claimed in  claim 28 , wherein the speech feature extraction block comprises means for obtaining cepstral features. 
     
     
         32 . A microphone unit as claimed in  claim 28 , wherein the speech feature extraction block and the digital output are provided on a single integrated circuit. 
     
     
         33 . A microphone unit as claimed in  claim 32 , wherein the transducer is provided on said integrated circuit. 
     
     
         34 . A microphone unit as claimed in  claim 33 , wherein the transducer comprises a MEMS microphone. 
     
     
         35 . A microphone unit as claimed in  claim 28 ,
 wherein the transducer is for generating an analog audio signal,   further comprising an analog-to-digital converter, for generating a digital audio signal from the analog audio signal, wherein the speech feature extraction block is connected to the analog-to-digital converter, for obtaining speech feature values from the digital audio output signal.   
     
     
         36 . A microphone unit as claimed in  claim 35 , wherein the analog-to-digital converter is provided on said integrated circuit. 
     
     
         37 . A microphone unit as claimed in  claim 28 , further comprising data compression circuitry, for receiving said speech feature values from the speech feature extraction block, and for generating reduced bit rate signals for supply to said digital output. 
     
     
         38 . A microphone unit as claimed in  claim 37 , wherein the data compression circuitry operates using a predetermined code book. 
     
     
         39 . A microphone unit as claimed in  claim 37 , wherein the data compression circuitry performs multi-vector coding. 
     
     
         40 . A microphone unit as claimed in  claim 28 ,
 wherein said digital signals contain data at 20k bits/second or lower.   
     
     
         41 . A microphone unit as claimed in  claim 28 , wherein the digital output is configurable in a first mode, for supplying said digital signals representing said speech feature values, and in a second mode, for supplying digital signals representing time samples of said audio signal. 
     
     
         42 . A microphone unit as claimed in  claim 28 , wherein the digital output is configurable in a first mode, for supplying said digital signals representing a data compressed version of said speech feature values, and in a second mode, for supplying digital signals representing time samples of said audio signal. 
     
     
         43 . A microphone unit as claimed in  claim 42 , wherein said digital signals representing the data compressed version of said speech feature values comprise ADPCM compressed data. 
     
     
         44 . A microphone unit as claimed in  claim 41 , wherein the digital signals representing time samples of said audio signal are supplied at a higher data rate than the digital signals representing said speech feature values. 
     
     
         45 . A microphone unit as claimed in  claim 44 , wherein the digital signals representing time samples of said audio signal are PCM signals supplied at a sample rate of 16 kHz or higher. 
     
     
         46 . A microphone unit as claimed in  claim 44 , wherein the digital signals representing time samples of said audio signal are PDM signals at a sample rate of 0.5 MHz or higher. 
     
     
         47 . A microphone unit as claimed in  claim 42 , wherein the digital output is configurable between the first mode and the second mode based on a command received from a separate device to which the digital output is connected. 
     
     
         48 .- 73 . (canceled)