Pitch is determined by vibration frequency. A guitar string vibrating at 440 times a second will product a perfectly tuned "A" note. A string vibrating any faster than this will produce a higher...
Sound is made when air is forced through the vocal chords at the top of the larnyx. The chords sit atop the trachea. When they are constricted, you make a squeeky sound. When they are relaxed, you...