No claims have ever been made for doubly articulated flaps or trills, such as a simultaneous alveolar–uvular trill, , and these are not expected to be found. Several claims "have" been made for doubly articulated fricatives or affricates, most notoriously a Swedish phoneme which has its own IPA symbol, . However, laboratory measurements have never succeeded in demonstrating simultaneous frication at two points of articulation, and such sounds turn out to be either secondary articulation, or a sequence of two non-simultaneous fricatives. (Despite its name, the "voiceless labial-velar fricative" is actually a voiceless approximant; the name is a historical remnant from before the distinction was made.) Such sounds can be made, with effort, but it is very difficult for a listener to discern them, and therefore they are not expected to be found as distinctive sounds in any language.