| Description |
This study involved conducting experiments to obtain a clear, high-amplitude acoustic signal through the use of a new design of thermoacoustic converter. The thermoacoustic converter used photoacoustic effects to generate sound from solar energy within frequency range 200-3000 Hertz (Hz). The amplitude range of the thermoacoustic signal in this experiment was 86.5 decibel (dB) to 98.3 dB. The thermoacoustic energy conversion system consisted of a lens and a chopper wheel to create air pressure fluctuations inside a thermoacoustic converter attached to a small microphone. Though a high-amplitude signal was produced, the signal was contaminated with noise. Over the course of the study, new electric cables, insulation materials, and a shock mount were added to the converter and microphone to reduce noise. In later experiments, light- and heat-reducing window films were used to control the amount of solar radiation entering the converter to ensure production of a sine wave in frequencies 200-3000 Hz. The author performed Fast Fourier Transform (FFT) and time-domain analysis on the signal using LabVIEW and MATLAB software. Analysis revealed that: the noise reduction techniques (shock mount device, insulation materials, and new set of electric connection cables) were effective in significantly reducing the background noise; the new thermoacoustic converter design was effective in creating a loud, clear sound; and the geometry of the thermoacoustic converter was critical for increasing the amplitude of the sound. After implementing noise reduction techniques, noise amplitude was reduced by 93%. The amplitude of the signal was improved by 83% for frequencies 200-3000 Hz but only 60% for frequencies 1000-3000 Hz. In particular, it was found that the reduction of vibration through use of the shock mount device improved the thermoacoustic (TA) laser signals considerably. With noise reduction techniques, the relationship between the amplitude and frequency of the thermoacoustic signal decreased nearly linearly within frequency range of 1000-3000 Hz. Finally, calibration procedures were conducted to convert Volt units to dB units, measure the loudness of the signal at specific frequencies, and compare it with previous research. |
