DEVELOPMENT OF AUDIO SYSTEM TO STUDY THE COEFFICIENT OF ATTENUATION OF SOUND WAVES IN AIR

Abstract

Audible sound waves travel farther in dry air than in moist air; as attenuation occurs due to the presence of atmospheric water vapour. To study the rate of attenuation, an audio equipment was developed which is made up of: a variable audio oscillator with less than 0.2% distortion in the frequency range 20Hz to 50kHz, a 50Watt audio power amplifier with total harmonic distortion (THO) less than 0.1 % to drive the transmitting device and a .linear sound pressure meter as the receiver: The sound pressure meter was found to be accurate to within ±3dB in the range 50dB to 120dB.The audio equipment was set up for some months and from the data collected, the attenuation coefficient of sonic waves traveling in the atmosphere was found to be between -0.0063dB and -0.0311dB per meter.