Mechanical Pressure‐Gradient‐to‐Pressure Sound Transducer

In places of high ambient‐noise level, the use of electrical devices as an aid to speech communication is sometimes precluded by safety requirements. A mechanical device may then be used provided that the individuals concerned are close to each other. Such a device can be made to incorporate all the acoustical benefits of a dose‐talking microphone. Sentence intelligibility tests showed that when the articulation index was zero for a nearby speech source the median subject obtained a score of 28% using ear covers alone and 84% with the sound transducer; the subjects with extreme scores improved from 0 to 14% and from 88 to 100% respectively. No subject using the device suffered a decrease in intelligibility.