“发颤音”用英语怎么说

这是个发颤音的字母.This is a letter with a trill.在声音上它们基本算得上安静, 然而高兴时它们会发颤音 、 唧唧声和短而轻的声音.They are basically quiet cats in voice, however they do trill, chirp and click when delighted....