Wind - Wind gives the illusion that a sound is coming from a different direction than it really is. This creates a re<ant propagation vector (see diag. 1). When sound propagates with the wind it tends to refract downward, and against the wind refract upwards (see diag. 2), (*refractionis the term used to describe the bending of sound).
ISS WlND | CROSS WlND |
SOU
From the speakers to our ears - Since you usually want a target background SPL of about 70dB - 80dB to your listeners, keep in mind the Inverse Square Law, which states that in a free field with no walls, floor, or ceiling, the intensity of sound decreases with the square of the distance. For example when you double the distance between the speaker and your listener'sear, the SPL decreases by 6dB (i.e. If a speaker's output is100dB SPL at 10 feet away, at 20 feet away the SPL is decreasedto 94dB.) Don't forget, a1OdB drop will sound "half as loud".
PROPAGATION '
VECTOR
CROSS WlND
Temperature - Temperature differences also have a small effect'onsound propagation. Hot air is less dense than cold.
travels faster in a less dense medium and therefore up as air gets warmer, and slows down as air gets