voices have referred only to the cases of voiced phones since unvoiced phones consonants produced without the vibrations of the vocal cords have their spectra in a higher frequency band they are cut by the low pass filter for deriving the body felt vibration signal having the cutoff frequency of approximately 150 hz and cause no problem the low pass filter 3 in fig1 or fig3 even in the cases of voiced phones voices of high fundamental wave frequencies such as children 39 s voices female voices and high pitched voices given forth in singing a song cause no problem for the same reason it has been experimentally verified that the difference of the distinguishabilities based on different languages is scarely noted which is thought to owe to the same reason shown in fig7 is block diagram of a practical circuit for performing this invention in which the elements of both the circuits in fig1 and 3 are combined in this case two input terminals 1 are disposed so as to receive signals through two channels and to mix them by means of a mixer circuit 24 connected on the output side of the mixer circuit 24 is a subsonic filter 25 for removing unnecessary subsonic waves of and below 20 hz the output side of the subsonic filter 25 is branched into a circuit towards a voltage controlled variable gain amplifier 4 through a low pass filter 3 for deriving a body felt vibration signal having a cutoff frequency of 150 hz and a circuit towards an equalizer circuit 26 the equalizer circuit 26 gives the double bass.