Methods to study pre-school teachers' voice at work: simultaneous recordings with a voice accumulator and a DAT recorder

Long-term recordings with reliable methods are desirable for objective documentation of voice use during natural conditions. The purpose of this study was to evaluate a voice accumulator (VAC) with a digital audiotape (DAT) recorder as a reference. The VAC is based on a microprocessor that accumulates information about fundamental frequency (F0) and phonation time. A contact microphone attached to the front of the neck registers vocal fold vibrations. The DAT recorder was connected to two microphones for airborne signals placed at equal distance from the mouth close to the subject's ears. The computer program Aura was used to separate the subject's voice from the background noise. The Soundswell program was used for F0 and phonation time analysis. Two tests were performed: 1) One female speech-language pathologist was recorded with the two devices simultaneously in a sound-proof booth. She read a standard text with different voice qualities and sustained vowels with increasing F0 and intensity separately. The results showed good agreement between the two methods with respect to F0 and phonation time. However, the VAC failed to register high frequencies above around 440 Hz as well as low intensities. 2) Three female pre-school teachers were recorded with the two devices simultaneously during a working day. Results showed high correlations between the two methods in terms of long-term measurements of F0 and phonation time for two subjects For one subject with subcutaneous soft tissue on the neck, the registration with the contact microphone was not reliable. It was concluded that the VAC has potential for assessment of occupational voice disorders if certain limitations of the method are considered.