but sonar scans texture too, :S

But you say, if string... then play the sound 1
but you don't exclude others..
you should do this..
if( str_cmpni(tex_name,tex_a) == 1){play sound a}
if( str_cmpni(tex_name,tex_b) == 1){play sound b}
etc.. so if there is no =1 then no sound defined for texture.