Vid undersökandet av röstkällan, och då framförallt röstkvalitet ur ett lingvistiskt perspektiv, är inspelning med accelerometer, eller strupmikrofon, en lovande metod som dock är i behov av förbättring. En ännu okänd aspekt är om vokalkvalitet påverkar korrelationen mellan sig- nalerna från strupe och mun, vilket denna studie ämnade klargöra. I studien ingick 8 friska, vuxna försöksdeltagare som fick yttra sekvenser av /pa/, /pi/, /pu/ och /pæ/, med olika intensi- tet, 3 olika tonhöjder och röstkvaliteterna modal, läckande och pressad. Resultaten visade att en regressionsmodell som tar hänsyn till vokalkvalitet har lägre MAE (en förbättring med i genom- snitt 0,34 dB SPL) och högre R2 än en baselinemodell utan någon interaktionsvariabel. Slutna vokaler tenderade att ha en flackare regressionskurva än öppna vokaler. Motsvarande modell gjordes också för röstkvalitet, och även den visade sig vara något bättre än baselinemodellen, dock utan särskilt tydliga tendenser. Vokalkvalitet har således en signifikant, men liten, effekt på förhållandet mellan accelerometer- och mikrofonsignal.

Contact microphones, especially throat microphones, have been developed to be used in environments with high background noises to improve the speech intelligibility in communication. They pick up vibrations from the surface they are attached to and are therefore less sensitive to sound and noise from the air. Comparison of the speech intelligibility with other types of microphones have previously been done by letting test persons examine the communication devices in question. This study examines the possibility to make use of the STI-method instead and therefore make a comparison faster, more cost-efficient and customizable. The thought is that if the relationship between speech signals and vibrations were known, it could be used to transform the STI test signal to vibrations and then use the STImethod to estimate the speech intelligibility for the chosen contact microphone. This study, containing 22 men and women, evaluated the vibrations at the most suitable locations on the head for contact microphones and compared it with the speech signal of the same test person. Frequency responses were calculated for all locations of the head and a more detailed study showed that the frequency response of the neck may be approximated as a second order lowpass filter with a cut-off frequency of about 300 Hz that attenuates speech signals with higher frequencies. Experiments were also done to measure the STI value of a throat microphone with the known relationship. However, the results pointed out several problems that needs to be addressed before a STI method can be performed successfully. The results from this study may also be used to deeper study the relationships between different vibrations resulting from speech signals and suggestions on how the performance of contact microphones may be improved are given.