The purpose of this experiment is to determine the speed of sound.
The apparatus is a PVC tube (sometimes refered to as "Kundt's tube"), with 1458 millimiters in length. On one end there is a fixed speaker that can produce an audio sine, triangular or a single pulse wave. On the opposite side there is a movable piston, changing the effective lenght of the tube. Along the tube there are several microphones to register the sound intensity at fixed points.
The following table shows the positions of the microphones in relation to the speaker:
Referência Distância à fonte (altifalante) Mic 1 (referência) 250 mm Mic 2 (centro do tubo) 750 mm Mic 3 (extremidade do tubo) 1250 mm Mic 4 (superfície do êmbolo) Entre 1260 e 1480 mm Extremidade do tubo 1450 mm Table 1 – Microphones distance to the sond source (speakers membrane)
The reference mic (Mic 1) should be used to verify that the emitted sound is the disered on (i.e., there is no distortion caused by the speaker). On the piston surface is another microphone (Mic 4) capable of moving between 1269mm and 1475mm. The sound is aqquired through 2 channels of a sound card: the left channel (CH 1) is always bounded to the reference microphone (Mic 1); the other channel (CH 2) can be connected to one of the other three microphones.
The experimental data is captured by the soundcard and processed online (normalization).This assembly is also used for the stationary wave experiment, and thus has two modes of operation: in the "Speed of sound" mode, the amplitude of the wave is registered through time.
To determine vsound, the user must choose a "pulse" type of stimullus and measure the time that takes the wave between Mic 1 and one of the other microphones. The speed can be determined with the data from table 1 and the formula:
\[ v_{sound} = \frac{\Delta}{\Delta t} \]
Under construction.
