Sound level meters or noise dosimeters are electronic measuring devices for measuring sound pressure in decibels( dB). They are devices with which the sound pressure level can be evaluated according to certain characteristics. Because of the disturbing and possibly also health-endangering effects that sound, or noise, can have on people, the sound evaluation can be carried out in terms of frequency according to specified frequency patterns or also in terms of time as a short-term or long-term recording.
Measuring instruments for sound and noise
Sound level meters are used in sound, noise and noise measurement to protect people against noise pollution in the home and at the workplace. This can be road and aircraft noise, noise in the office and workplace generated by machinery, equipment or production lines, or noise from catering establishments or from neighbors.
All applications require that the measurement takes place at the point of origin with mobile sound level meters. There are various German and EU guidelines for sound level measurement and the permitted limit values. The Workplace Ordinance is one guideline for the protection of employees, the TA-Lärm from the Federal Immission Control Act is another, and the EU Directive on the "Assessment and Management of Environmental Noise" concerns the day-evening-night assessment, Day/Evening/Night (Lden).
The hearing perception of people
Since the perception of noise and loudness depends on the hearing sensation, some sound level measurements emulate hearing characteristics. This is the case with A-weighting, which corresponds to the hearing sensation at a volume of 40 phon, or B-weighting, which is designed for 60 phon to 100 phon, and C-weighting for values above 100 phon. Other evaluations that can be performed with sound level meters include structure-borne sound and impact sound and its propagation in ceilings, walls and floors, determination of the instantaneous sound event level and the maximum level of a sound event.
In addition, the noise level over a certain period of time also plays an important role. For the short-time evaluation, sound level meters have different time constants, which are anchored in the standards: Fast (F), Slow (S), Impulse (I). This evaluation is related to the fact that short-time sound impulses are perceived more disturbing than longer sound events. Long-term evaluation can take place over several days or months. For these measurements, sound level meters can be combined with data loggers on which the measurement results can be stored over longer periods of time.
In terms of construction, sound level meters consist of a measuring microphone with an isotropic directional characteristic, the microphone preamplifier with range switching and downstream weighting filters, an amplifier with squaring and time weighting, and the display. As with other measuring instruments, the display can be analog or digital. There are also devices that work with bar graph display. For automated measuring stations and measuring systems, there are sound level meters with common interfaces and bus systems.