Total Coat Canada: What Is Noise?

What is Noise?

Noise is often defined as unwanted sound, especially a loud or unpleasant sound. Sound is a mechanical wave which is created by pressure changes in a medium (usually air) in the form of vibration or turbulence. The vibration of the object set particles in the surrounding medium in vibrational motion, thereby transporting energy through a medium. In a vacuum there is no noise as there is no air through which the sound wave can travel.

The amplitude of these pressure changes is stated in terms of sound level, and the rapidity with which these changes occur is the sound's frequency. Sound level is measured in decibels (dB), and sound frequency is stated in terms of cycles per second or Hertz (Hz).

Sound level in decibels is a logarithmic rather than a linear measure of the change in pressure with respect to a reference pressure level. This means that a small increase in decibels can represent a large increase in sound energy. Technically, an increase of 3 dB represents a doubling of sound energy, and an increase of 10 dB represents a tenfold increase. The ear, however, perceives a 10-dB increase as doubling of loudness.

In general terms, a 10 dB reduction represents a 90% decrease in acoustical energy and sounds HALF as loud. A 5 dB reduction represents a 50% decrease in acoustical energy produced by the noise source and sounds about 30% quieter.

The effects of noise are determined mainly by the duration and level of the noise, but they are also influenced by the frequency. Adults hear sounds in the 50 to 12,000Hz frequencies, while verbal communication is in the 200 to 8,000Hz frequency range. Human hearing can distinguish differences in sound frequency best between 1,000 and 2,000Hz frequencies. Distinguishing differences between sounds in lower frequencies (30 - 500Hz) is more difficult unless the volume is higher. Road and mechanical noise is primarily around the 100 to 3,000Hz range and can make listening difficult.

Long-lasting, high-level sounds are the most damaging to hearing and generally the most annoying. High-frequency sounds tend to be more hazardous to hearing and more annoying than low-frequency sounds. An effective noise control solution will address all of these factors.