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A noise dosimeter (American English) or noise dosemeter (British English) is a specialized
sound level meter A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, whic ...
intended specifically to measure the
noise exposure Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Noise from traffic, in particular, is considered by the World Health Organization to be one of the worst environm ...
of a person integrated over a period of time; usually to comply with Health and Safety regulations such as the Occupational Safety and Health (OSHA) 29 CFR 1910.95 Occupational Noise Exposure Standard or
EU Directive The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
2003/10/EC.


Noise Measurement

Noise dosimeters measure and store
sound pressure level Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone ...
s (SPL) and, by integrating these measurements over time, provide a cumulative noise-exposure reading for a given period of time, such as an 8-hour workday. Dosimeters can function as personal or area noise monitors. In occupational settings, personal noise dosimeters are often worn on the body of a worker with the
microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public ...
mounted on the middle-top of the person’s most exposed shoulder. Area monitoring can be used to estimate noise exposure when the noise levels are relatively constant and employees are not mobile. In workplaces where employees move about in different areas or where the noise intensity tends to fluctuate over time, noise exposure is generally more accurately estimated by the personal monitoring approach. Dosimeters are also used to collect data for use in legal proceedings, development of engineering
noise control Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors. Overview The main areas of noise mitigation or abatement are: transportation noise control, ...
s, and other industrial hygiene purposes. When planning to conduct noise exposure measurements, steps must be taken to ensure that the dosimeters are calibrated and operated according to manufacturers’ specifications. It is also necessary to understand the properties of the acoustic environment, the main measurement objectives as they relate to determining the risk to
hearing damage Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken l ...
, and the limitations associated with the use of dosimeters. Dosimeter manufacturers recommend that the instrument be calibrated with an acoustical calibrator such as a pistonphone before and after each measurement to verify reliable operation. In addition to field calibration routines, the manufacturers recommend periodic comprehensive calibration and certification of the instrument by an accredited laboratory using traceable reference sources. Field calibration of contemporary dosimeters has been mostly automated through PC-based programs that run the calibration routine, document the time and date, and adjust for any offset in levels.


Occupational settings

Current dosimeters are designed to provide the user with parameters such as noise dose, time-weighted average,
sound exposure level Sound exposure is the integral, over time, of squared sound pressure. The SI unit of sound exposure is the pascal squared second (Pa2·s). Mathematical definition Sound exposure, denoted ''E'', is defined by :E = \int_^ p(t)^2\, \mathrmt, where *t ...
, as well as peak, maximum, and minimum sound pressure levels. Most dosimeters also generate statistical and graphical representations of the collected data. ANSI S1.25 specifies that dosimeters should at least provide the following parameters: Frequency weighting:
A-weighting A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured ...
or
C-weighting A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured ...

Exponential averaging: F (fast); S (slow)
Criterion level: 90, 85, 84, 80, or V (variable)
Criterion duration: Hours
Threshold level: 90, 80, or V (variable)
Exchange rate: 5, 4, or 3 A noise or sound dose is the amount of sound a person is exposed to in a day. The dose is represented by a percentage. A noise dose of 100% means that a person has exceeded the permissible amount of noise. Any noise exposure after the 100% noise dose may damage hearing. The exchange rate is the rate at which exposure accumulates. An addition of the exchange rate results in a halving of exposure time. The following table represents the exposure levels for occupational organizations as of November 2018:


Standardization

The international body that specifies the technical requirements of such instruments as sound level meters and dosimeters is the
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
(IEC) based in Geneva; whereas the method of their use is normally given in an
International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...
(ISO) publication. In the U.S., the
American National Standards Institute The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
(ANSI) ANSI S1.25-1991 (R2007) specifies the performance characteristics of personal noise dosimeters.


Use of dosimeters

The original dosimeters were designed to be belt worn with a microphone connected to the body of the dosimeter and mounted on the shoulder as near to the
ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...
as practicable. These devices were worn for the full work shift and at the end would give a readout initially in percentage dose, or in some other exposure metric. These were the most common way of making measurements to meet legislation in the USA, but in Europe, the conventional sound level meter was favoured. There were many reasons for this, but in general in Europe the dosimeter was distrusted for several reasons, some being. * The cable was considered dangerous as it could catch on rotating machinery * The dosimeter could tell you the level had been exceeded, but it did not say when this happened * Workers could falsify the data very easily * The device was big enough to affect the work pattern In the USA – where most of the early devices were manufactured, these reasons did not seem to matter so much. To remove these European objections, dosimeters became smaller and started to include a data store where the Time History of the noise, usually in the form of Short
Equivalent Sound Level Equivalence or Equivalent may refer to: Arts and entertainment *Album-equivalent unit, a measurement unit in the music industry * Equivalence class (music) *'' Equivalent VIII'', or ''The Bricks'', a minimalist sculpture by Carl Andre *''Equiva ...
(Leq) was stored. This data could be transferred to a personal computer and the exact pattern of the noise exposure minute by minute plotted. The usual method used was to store data in the form of Short Leq, a French concept that helped to bring computers into acoustics. As well, dosimeters started to incorporate besides the A-weighting a second C-frequency-weighted channel that allowed the true peak to be indicated. By the time the PSEM standard was published, many major sound level meter companies – in both Europe and the USA had a dosimeter in their range. Noise dosimeters are worn by workers in order to track their sound exposure over a period of time. With the accuracy of a type 2 sound level meter, a majority of noise dosimeters measure within ±2 dB A. One must make sure to the noise dosimeter is properly calibrated and kept out of extreme temperature and humidity. The noise dosimeter is typically programmed by a hearing conservationist, sound engineer or audiologist. When the professional is setting up the noise dosimeter, settings like frequency of sound sampling and log information should be considered. When placing any dosimeter, the microphones should be clipped to the shoulder with the microphone facing upwards. The microphone should be placed in the open and clear from any surrounding fabric. It should also be protected from any wind source when outdoors and should have a wind screen over it for protection if needed. Over the course of the day, the dosimeter will measure the time-weighted average of the sound level the user experienced. It is important to make sure the batteries are fully charged since the dosimeter often has to run for 8 to 10 hours over the course of the work shift. Noise dosimeters do not record the user's voice, so it is important to teach the user how to operate and successfully use the device so the end result is not influenced by the user's tampering.


Companies

The following major manufacturers are among those who offer noise dosimeters: * Denmar
Brüel & Kjær
* United Kingdo
Castle Group Ltd
* United Kingdo
Casella CEL Ltd.
* United Kingdo
Cirrus Research plc
* United Kingdo
Pulsar Instruments plc
* US
3M
* US
Larson-Davis
* Franc
01dB-Metravib
* Polan
SVANTEK
* Japa
RION CO., Ltd


References

{{Reflist Dosimeters Sound measurements Noise pollution