I have a question, I read that the human ear can hear frequencies from around 20hz to 20,000hz. Is this just sine wave? Or would half wave square wave be different. Such as if I have a spark gap firing at 5 hz would I would assume I could hear that, but what is the definition of infrasonic? I always thought of hertz as beats per second or am I dead wrong? Also how could I play infrasonic on subs?