Help Topics - E

Ear

Cross section of the typical human ear showing the hearing mechanism that concentrates the sound waves and directs them to the inner ear for detection and recognition as speech or music or warnings.

- -

Ear muffs

Personal hearing protectors that are worn over the whole of the outer ear to minimize hearing loss in high noise levels. These hearing protectors are usually connected by a strong metal band to maintain an adequate tight fit over the ears.

- -

Ear plugs

Personal hearing protectors that are worn inside the ear canal of the outer ear to minimize hearing loss in high noise levels. These are usually made of foam that is first compressed and then inserted into the ear canal where they can expand and take up the right shape for each ear they are used in.

- -

EC

The European Community.

- -

Echo

A wave that has been reflected or otherwise returned with sufficient magnitude and delay so as to be detected as being distinct from the direct wave at the point of interest. If the echo arrives too late after the direct wave then the intelligibility of the sound or speech will be adversely affected.

- -

Ecosystem

The interacting system of a biological community and its non-living environmental surroundings.

- -

Enclosure

A complete box structure around a noise source for the purpose of keeping the noise levels at a certain point lower than they would otherwise be without the enclosure. Typical enclosures are constructed from wood, metal, brick depending upon how much attenuation of the source noise is required to be obtained.

- -

EPA

The Environmental Protection Agency in the USA.

- -

Epidemiology

Study of the distribution of disease, or other health-related states and events in human populations, as related to age, sex, occupation, ethnic, and economic status in order to identify and alleviate health problems and promote better health.

- -

Equal loudness curves

Lines of equal sensation of loudness plotted on a chart of decibels versus frequency to show the subjective impression of different sounds. The human hearing mechanism is less sensitive to sound at low and high frequencies and more sensitive to the range of frequencies between 250 to 5,000 Hz. The equal loudness curves vary in gradient depending upon the overall level of noise becoming more linear as the noise level rises.

- -

Equivalent continuous noise level

The single notional constant level in decibels that represents the same sound energy as the actual varying sound over a specified interval of time. The steady level Leq is equivalent in energy to the "real" actual varying noise level over the specified period of time. The Leq is usually expressed as an ‘A’ weighted value in dB unless the frequency response is specified otherwise, e.g. LCeq. The Leq can also be measured in individual octave or third octave bands during a frequency analysis of a noise source for noise control purposes.

- -

Equivalent method

Any method of sampling and analyzing for air pollution which has been demonstrated to the relevant regulators satisfaction to be, under specific conditions, an acceptable alternative to normally used reference methods.

- -

Errors

When properly defined, the term “error” pertains only to physical measurements, that is to estimating anything where exactness is not possible. Measurement errors are unavoidable even for the most thoroughly trained and motivated measurer. They occur to some extent in virtually every physical measurement because of imperfections of the instruments used and the person undertaking the measurement, as well as the influences of the natural environment. Errors may be defined in terms of a fixed error or as a percentage of the reading taken. Errors in a measurement system can be systematic or random depending on the cause.

- -

EU

The European Union.

- -

Exceedance noise level

The calculated noise level based on sampling the varying noise climate and expressing the result as a percentage of time above the chosen statistical level. For example, the LN10% is the noise level exceeded for 10% of the measured time interval. The samples of the noise are sorted into a distribution table at fixed dB intervals and the statistics are calculated from the cumulative distribution curve that is produced. The LN90% is often used to describe the background noise level in noise measurements.

- -

Exchange rate

This is the number of decibels used in the calculation of the average noise level that is taken to represent the doubling (or halving) of the risk when used in personal noise dosimetry measurements. Possible values for the exchange rate are currently 3, 4 or 5 decibels. An exchange rate of 6 dB is very occasionally found in certain instruments but is not commonly used.

- -

Extractive monitoring

Measurement made on a sample that is taken from a stream or flow.

- -