Technical considerations in the design of a wearable voice dosimeter

This paper deals with the technical issues involved in the design of a voice dosimeter, a wearable device to be used by teachers to measure vocal dose on the job, at home and elsewhere during the total waking hours of each day. The concept of vocal dose is introduced and definitions of various dose measures are presented. Practical issues of the design are discussed, including software development, selection of an external transducer, and devising a comfortable, reliable and repeatable means of attaching the transducer to the subject. The dosimeter software was designed to calculate SPL (sound pressure level), F0 (fundamental frequency) and voicing time. In addition, an interactive portion was developed that prompts the user to verify the validity of the stored data every two hours, and to perform a rating of vocal effort and quality of soft phonation. The SAL (surface acceleration level) to SPL relation for the prototype dosimeter was determined. The prototype has been field-tested, and SPL, F0, and voicing time data have been analyzed. A sensitivity analysis shows that small errors in SPL have a large effect on the accuracy of dose calculations, while F0 errors have less of an effect.