Found this script to do it as well, allows for different sounds for each terrain tag. Not sure if it would cause less lag or not:
CODE
## Step Sounds - Brew 01AUG10 (ref: Project3)
## Play a different sound with each terrain type
## You must have a file "terrain_x.ogg" in the Audio\SE folder
## Where 'x' is the terrain number. (1-7)
class Game_Player
alias step_sounds_increase_steps increase_steps
def increase_steps
step_sounds_increase_steps
## Frequency of sound effect. % 2 approx. every 0.5 seconds
## % 4 would be approx. every 1 second
if $game_party.steps % 2 == 0
if terrain_tag > 0
#play the sound for that terrain
if FileTest.exist?("Audio/SE/terrain_" + terrain_tag.to_s + ".ogg")
Audio.se_play("Audio/SE/terrain_" + terrain_tag.to_s)
end
end
end
end
end