Noise and Ultrasound

Noise is America's most widespread nuisance. But excessive noise is more than just a nuisance. Day and night, at home or at work or play, excessive noise exposures annoy individuals, produce stress, impair our ability to communicate, interfere with work and play activities, and, in high enough doses, produce permanent damage to the auditory system that can lead to significant hearing loss. Although annoyance caused by noise affects all of us to some degree, this chapter describes the effects of excessive noise on our ability to hear, and on the effects of ultrasonic stimulation on tissue. The chapter is organized in four sections. In the first, consideration is given to the physical characteristics of sound and the measurement of noise exposure. The second section considers the effects of excessive noise exposure within the range of human hearing, approximately 20 Hz to 20 kHz. In the third section, a review of the effects of infrasonic exposure (<20 Hz) is provided. And, finally, the last section reviews the effects of exposure to ultrasound (20 kHz to 20 μHz) on humans. Engineers and scientists are concerned with sound as an energy that can be measured and quantified; no consideration is usually given to whether the sound can be perceived by humans or not. However, hearing health professionals are usually concerned about the effects of sound on humans: what and how we hear, what sounds please us, what sounds annoy us, what sounds interfere with our ability to communicate with each other and impair our productivity and work safety, and what sounds can be damaging to our hearing. These effects require different measures than “simple” quantitative descriptions of acoustic energy, and often are expressed in perceptual terms, like “loudness” or “pitch.” Keywords: acoustic cavitation; amplified music; biological effects; frequency; gunfire; hearing loss; hearing sensitivity; management; measurement; noise; noise exposure; nonoccupational exposure nonthermal effects; prevention; speech communication; speed of sound; sound; thermal effects; wavelength