Samuel Sonning, Thomas Mejtoft, Sten Ternström, Viveka Lyberg Åhlander (Sweden)

Reliability of voice SPL estimations with an air-coupled microphone fastened to the neck

Umeå University, KTH Royal Institute of Technology, Lund University

Some characteristics of the voice, such as the sound pressure level (SPL), can be estimated by means of an accelerometer or a microphone fastened to the neck. The relationship between acceleration level at the skin and SPL has been studied earlier. This study examined the relationship between SPL as measured by an air-coupled microphone fastened to the neck, and SPL as measured by a microphone placed at a fixed distance in front of the mouth, in order to determine the reliability of using the SPL value as measured at the neck as an estimate of voice SPL. Test subjects read out loud a text passage, and were recorded by a microphone fastened to the neck as well as by a reference microphone 30 cm in front of the mouth. The SPL values of the frames of the recording were compared in order to derive a linear model for the relationship between the measurements of the reference microphone and the neck-fastened microphone. The error when assuming slope = 1 and intercept = 0 was also quantified. The results show that there is a clear linear relationship between the variables, and that the errors when assuming the aforementioned model parameters are within reasonable bounds. They also show that there is some inter-subject variation, but that this variation might be small enough to motivate using a single model for prediction, depending on the application.

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