Determination of the Speed of Sound
Contents
Description of the Experiment
The purpose of this experiment is to determine the speed of sound.
Experimental Apparatus
The apparatus is a PVC tube (sometimes refered to as "Kundt's tube"), with 1458 millimiters in length. On one of the extermities there is a fixed speaker that can produce an audio sine or triangular wave or a single pulse. On the opposite extremity there is an embolus that can move, changing the effective lenght of the tube. Thruogh out the tube there are several microphones to register sound intensity.
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 Tabela 1 – Distância dos microfones à fonte (altifalante)
The reference mic (Mic 1) should be used to verify that the emitted sound is the correct on (i.e., there is no distortion caused by the speaker). Inbued in the embolus is another microphone (Mic 4). The former can move 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).Protocol
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 \( v_{sound} \), 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:
\[ v_{sound} = \frac{\Delta}{\Delta t} \]
Advanced Protocol
Data Analysis
Theoretical Principles
Historical elements
Bibliography
Under construction.
