Posts Tagged ‘measurements’
Noise refers to any unwanted sound that is unpleasant to the mind and ears. It is always best to keep the noise levels under control to have a pleasant and peaceful mind. In our daily life, nearly all equipment produce noise, however, noise produced in audio equipment such as microphone, amplifiers and recording systems should be very low.
Recording studios, radio stations and other commercial places use noise measuring equipment for producing good results. There are many types of noise measuring equipment suitable for measuring environmental noise, community noise, music noise, machinery noise, and road vehicle exhaust noise. Some measuring equipment is useful for testing fire alarms, pyrotechnics, and fireworks. While some noise test equipment is used for quality control of engines, gearboxes, axles etc.
Due to the fact that noise contains energy spread over a wide range of frequencies and levels, a simple level meter or voltmeter does not produce useful results instead a special noise-measuring instrument is required. The instruments for measuring noise include sound level meters, noise dosimeters and auxiliary equipment. The sound level meter is a basic instrument which is an electronic instrument consisting of a microphone, an amplifier, various filters, a squaring device, an exponential averager and a read-out calibrated in decibels (dB).
Sound level meters are categorized by their precision a type 0 is the most precise while type 3 is the least precise. In laboratories a type 0 meter is used, while a type 1 meter is used for other precision sound level measurements. Type 2 is the general purpose meter, and type 3 is the survey meter, which is not recommended for industrial use.
Sound level meters have built-in frequency weighting devices that allow most frequencies to pass. The A-weighting network is the most commonly used filter which simulates the response curve of the human ear at moderate listening levels. These meters offer different levels of meter responses to choose from.
The “slow” response comes has a 1-sec time constant, whereas the “fast” response has a 0.125-sec time constant. The “impulse” response has a 35 ms response for the increasing portion of the signal and a 1500 ms time constant for the signal’s decay. Results are displayed in the form of a graph on the screen of the measuring equipment. Lately, sound level meters are becoming increasingly small portable devices that can be easily connected to a range of software and via a range of communications options.