Actually I was walking on my roof and have heard some kind song coming from far distant loud speaker. Which getting louder sometime(sometime air blowing to me at that instant) and sometime getting very fainter.Is this happening for air blowing?Or somekind direction change by reflection or refraction of sound? . Can I determine the distance of the source of the sound by measuring the speed of air and variance of sound intensity ?
If the loudness changes relatively quickly it's most likely wind. Sound waves travel relative to the fluid (air). If the fluid itself moves the shape of the waves changes relative to a stationary observer.
Wind blowing towards you decreases the apparent distance since the wind speed adds to the speed of sound. Since the pressure falls with the inverse of the apparent distance, reduced distance will make it sound louder
Sometimes lateral wind can also move you in or out into the main "beam" of the sound source. Sound sources have a directivity and wind changes the shape of the polar pattern. Case in point: in outdoor concerts sometimes strong lateral wind modulates the high frequencies: the high frequency horns create a relatively narrow beam and the wind bends this beam away from the listener.