This month's issue of The Journal of the Acoustical Society of America (JASA), one of the world's most prestigious journals on acoustics and phonetics, features an article by Fryske Akademy researchers Cesko Voeten, Wilbert Heeringa, and Hans Van de Velde.

In order to compare acoustic measurements of vowels from different individuals in research on language variation, it must be ensured that physical differences between speakers do not affect those measurements. At the same time, linguistic (such as the influence of the next consonant), social (such as age) and geographical differences do need to be preserved. Scientists have developed various statistical methods to do so in recent decades. Voeten, Heeringa and Van de Velde compare sixteen common methods in their article 'Normalisation of nonlinearly time-dynamic vowels'. They show which methods are preferable and argue that the best choice partly depends on the researcher's precise goals. Those methods are also built into Visible Vowels, the software package for vowel normalisation and visualisation that has been developed at the Fryske Akademy for several years by Wilbert Heeringa and Hans Van de Velde.
 
With these results, they can optimally shape future analyses of phonetic variation in Frisian. At the same time, they offer researchers from all over the world a guide and tool for conducting research on vowel variation.

Since 1929, The Journal of the Acoustical Society of America has been the leading source of theoretical and experimental research findings in the broad interdisciplinary field of sound. The open access article 'Normalisation of nonlinearly time-dynamic vowels' by Cesko Voeten, Wilbert Heeringa, and Hans Van de Velde is published in the November issue (Volume 152, Issue 5) and is also available as a pdf.

This research has been made possible by the impulse contribution of the Province of Fryslân.