Works only with external speakers

I bought this while on a camping trip. Installed on an iphone4. With the phone only it was totally uneffective. However with a portable speaker/docking station by Logiteck Model EA942 resting on my lap while on a lounge chair in a mosquito infested woods at dusk, they stayed away. (From me only, not those around me)

Ken Nor about Anti Mosquito 3.1