**Our sense of whether a sound is “high” or “low”**
–Determined by vibration frequency: hertz (Hz) or cycles/second
–Human hearing range is 20 to 20,000 Hz
•Infrasonic frequencies below 20 Hz, Ultrasonic frequencies above 20,000 Hz
–Speech is 1,500 to 5,000 Hz, where hearing is most sensitive
–Most hearing loss with age is in range of 250 to 2,050 Hz