Voice activated multiple microphone electroacoustic amplifier system

DETAILED DESCRIPTION I claim: 1.
An electroacoustic amplifier arrangement comprising: a plurality of microphone arrangements, each microphone arrangement comprising a microphone with each of the microphones connectable to an input of an amplifier means having an adjustable gain factor and an amplifier output coupled to a loudspeaker arrangement for driving at least one loudspeaker associated with the loudspeaker arrangement, a threshold signal generator means for generating at its output a threshold signal, a microphone arrangement further comprising: coupling means for selectively coupling an output of an associated microphone to the input of the amplifier means as a function of the presence or absence respectively, of a control signal, comparing means having a first input coupled to the output of the microphone, a second input coupled to the output of the threshold signal generator means and an output coupled to a control signal input of the coupling means whereby the comparing means compares a microphone signal fed to the first input with the threshold signal fed to the second input and in response generates the control signal, and wherein the coupling means couple the output of the microphone to the input of the amplifier means in the presence of the control signal and to a further microphone arrangement of the electroacoustic amplifier arrangement, wherein the threshold signal generator means has a first and a second input coupled to the amplifier means and is arranged to derive from the signals applied to its first and second inputs a threshold signal as a function of the gain factor adjusted in the amplifier means.
2.
An electroacoustic amplifier arrangement as claimed in claim 1, wherein the threshold signal generator means derives a threshold signal from the signals applied to its first and second inputs which is determined in part by the contribution of the acoustic transfer of the acoustic signals from the loudspeaker arrangement to a microphone which is the result of a diffuse sound field present in a room in which the amplifier arrangement is installed