What is noise

Also if there are hard surfaces that can reflect the sound e. Sound pressure is usually expressed in units called pascals Pa. A healthy, young person can hear sound pressures as low as 0. A normal conversation produces a sound pressure of 0.

A gasoline-powered lawn mower produces about 1 Pa. The sound is painfully loud at levels around 20 Pa. Thus the common sounds we hear have sound pressure over a wide range 0. It is difficult to work with the broad range of common sounds pressures 0. To overcome this difficulty we use decibel dB, or tenth deci of a Bel. The decibel or dB scale is more convenient because it compresses the scale of numbers into a manageable range.

Sound pressure converted to the decibel scale is called sound pressure level Lp. Appendix A gives a detailed explanation of decibels and sound pressure levels. Figure 2 compares sound pressures in pascals and sound pressure levels in decibels dB. The zero of the decibel scale 0 dB is the sound pressure of 0. This means that 0. This is the reason the decibels of sound are often indicated as dB re 0.

The sound power is the sound energy transferred per second from the noise source to the air. A noise source, such as a compressor or drum, has a given, constant sound power that does not change if the source is placed in a different environment. Power is expressed in units called watts W. An average whisper generates a sound power of 0. Like sound pressure, sound power in W is usually expressed as sound power levels in dB. Appendix B provides examples of sound power level calculations.

Figure 3 relates sound power in watts to sound power level in decibels. Note that while the sound power goes from one trillionth of a watt to one hundred thousand watts, the equivalent sound power levels range from 0 to dB. Because the sound power of a noise source is constant and specific, it can be used to calculate the expected sound pressure.

The calculation requires detailed information about the noise source's environment. Usually a noise source with a lower sound power generates less sound pressure. For example, from the sound power of a compressor, one can calculate the expected sound pressure and sound pressure level at a certain location and distance. This information can be helpful in determining possible noise exposures and how they compare to the noise guidelines.

The manufacturer can often provide noise emission data such as sound pressure levels under standard conditions and the sound power of equipment. A number of international standards are available for labelling machines and equipment with their noise emission levels. In addition, Health Canada has issued a notice to stakeholders recommending that this noise data be included in the technical sales literature and instructions for use of machinery intended for a workplace.

Noise can be continuous, variable, intermittent or impulsive depending on how it changes over time. Continuous noise is noise which remains constant and stable over a given time period.

The noise of boilers in a power house is relatively constant and can therefore be classified as continuous. Most manufacturing noise is variable or intermittent. Different operations or different noise sources cause the sound changes over time. Noise is intermittent if there is a mix of relatively quiet and noisy periods.

Impulse or impact noise is a very short burst of loud noise which lasts for less than one second. Gun fire or the noise produced by punch presses are examples of such noise. The sensitivity of the human ear to sound depends on the frequency or pitch of the sound.

People hear some frequencies better than others. If a person hears two sounds of the same sound pressure but different frequencies, one sound may appear louder than the other.

This difference occurs because people hear high frequency noise much better than low frequency noise. Noise measurement readings can be adjusted to correspond to this peculiarity of human hearing.

An A-weighting filter which is built into the sound measuring instrument de-emphasizes low frequencies or pitches. Decibels measured using a sound meter equipped with this filter are A-weighted and are called dB A. Legislation on workplace noise normally gives exposure limits in dB A. Table 2 lists examples of typical noise levels. The decibel [dB, and also dB A ] is a logarithmic scale. This value is designated as dB A. The dB A is often used as it reflects more accurately the frequency response of the human ear.

A perceived loud noise has a high dB or dB A value and a soft noise has a low one. Copyright : Environmental Protection Department. All rights reserved. What are the common types of environmental.

What are the principles of controlling. How can various noise problems be tackled? What can you do to help reducing noise? When one plays a musical instrument, say a guitar, the vibrating chords set air particles into vibration. The vibration of air particles produces sound. Please click on the demo button to hear the sound. The landlord has been getting complaints from the tenants about noise. There were noises coming from the basement. The sink was making a gurgling noise.

Do you hear that rattling noise? The machine hardly makes any noise. The initial data included a lot of noise that had to be weeded out. Recent Examples on the Web: Noun The closed back design of these headphones and the plump ear cushions cut out a lot of unwanted background noise. Schmidt, Fox News , 3 Nov. Thursday through Saturday who respond to noise complaints.

First Known Use of noise Noun 13th century, in the meaning defined at sense 1c Verb 14th century, in the meaning defined at intransitive sense 1.

Buying Guide Our team at The Usage has selected the best soundbars of Learn More About noise. Time Traveler for noise The first known use of noise was in the 13th century See more words from the same century.

Phrases Related to noise background noise big noise make noise. Style: MLA. More Definitions for noise. English Language Learners Definition of noise. Kids Definition of noise Entry 1 of 2. Kids Definition of noise Entry 2 of 2.