The rule of material and obsolescence on flute tone quality has been discussed for a long time among musicians and flute makers. Mozart himself made use of crystal flutes in some of his works (Rondo’, K617, Adagio, K356). From an acoustical point of view, since Boehm’s work of 1832, the effect of material on flute tone quality has not been investigated, until researches of recent years [Coltman (1971); Chapuis (1991)]. In this work the research has been carried out measuring impulse responses inside the tube of the flute. Two different flutes have been utilized, i.e., a light‐alloy flute and a silver flute. The MLS sequences, with homemade software, have been utilized, gathering impulse responses in two different positions in the tube, in order to verify the variation of sound field. From the impulse responses a frequency analysis has been obtained, which pointed out that the silver flute contains more high frequency and shorter transient than the light‐alloy flute. Starting from the impulse responses, sound example of difference in sound quality has finally been obtained.