Construction an instrument detecting vibration wave of voiced sound, the transmitted wave passed though a stethoscope’s bell contacting a human neck is detected by condenser microphone and amplified. The signals have been analyzed by virtual spectrum analyzer developed of LabVIEW. By using the developed instrument detects and analyzes spectrum of vibration waves of the Thai comsonants voiced sounds.The instrument generally works well and the results are theoretically corresponded.There are some weakly responds with the vibration wave of short voiced sound,such as, the Thai vowel “sara อะ(Ah)” and “sara อิ(Ie)” .