A simple portable voiced, unvoiced and "s" indicator

This unit is called a V.S.F. indicator, the initials V.S.F. denoting Voiced "s" and Fricative indicator. It has been developed by the R.N.I.D. as an economical and portable speech training aid. A microphone is plugged into the device which classifies speech sounds on 3 lamps arranged vertically. The upper red lamp denotes voiced sounds. An amber light, centre, deonotes fricative sounds except "s" sounds which are indicated on the lower greeen lamp. The operation of the green light depends on the low frequency energy, while the amber and green lights are controlled by the rate of zero crossings. Informal trials in a variety of different types of special clinics have indicated that the most useful areas seem to be with profoundly deaf children and adults, although speech therapists have also reported promising reactions from children with a variety of communication disorders.