Noise tester

Noise Meter - Applications

The noise tester is an instrument used for noise detection and testing in public places such as work sites and squares. Noise pollution is one of the major environmental pollution problems. Higher decibel noise may even cause serious damage to the eardrum of the person, resulting in deafness. The application of a noise tester can provide the decibels achieved by the noise in order to take relevant measures to control and reduce the noise. The unit of measurement for the size of the sound is decibels. The professional noise tester has high-sensitivity sensors, high accuracy, wide application range, and can be widely used for noise measurement in various environments.

Selection of environmental noise monitoring instruments

In order to prevent and control noise pollution and ensure the quality of acoustic environment for life and work of urban and rural residents, the Ministry of Environmental Protection recently released

GB3096-2008 Acoustic Environment Quality Standard.

GB12348-2008 "Environmental Noise Emission Standards for Industrial Enterprises"

And GB22337-2008 “Emission Standard for Noise in Social Living Environment” was implemented on October 1, 2008.

In the above three environmental noise measurement standards, it is mentioned that the environmental noise monitoring instrument is an integrated average sound level meter or an automatic environmental noise monitor, and the performance thereof should not be lower than the requirements of GB3785 and GB/T17181 for Type 2 instruments. In the old sound level meter standards, the sound level meters were classified into 0-type, 1-type, 2-type, and 3-type according to the accuracy level. The new sound level meter standard classifies the sound level meter into levels 1 and 2 according to the level of accuracy. They are equivalent to the old Type 1 and Type 2 and no longer have Types 0 and 3.

In the GB12348-2008 and GB22337-2008 standards, it is also stipulated that noise less than 35dB should be measured using a type 1 sound level meter, and the measurement range should meet the needs of the measured noise, because the performance of the class 1 instrument is better than that of the 2nd class. The instrument is much better. For example, the difference between the accuracy of the two-level instrument and the one-level instrument may be 1.0 dB or more. In the new sound level meter standard, the operating temperature range of the Class 1 sound level meter is required to be -10°C to +50°C. Within this temperature range, the sensitivity change with respect to the reference temperature is not more than ±0.5dB; and the sound level 2 is The operating temperature range of the meter is 0°C to +40°C, and the sensitivity change with respect to the reference temperature is not more than ±1.0dB within this temperature range. Since most of the environmental noise monitoring instruments are used on site, the environmental conditions have changed greatly. Obviously, a class 1 instrument can meet the requirements of environmental noise measurement.

In the GB22337-2008 and GB12348-2008 standards, the indoor noise emission limits for structure propagation fixed equipment are proposed for the first time. It is stipulated that when the emitted noise propagates through a building structure into a noise-sensitive building room, the equivalent sound level in a noise-sensitive building interior It shall neither exceed the specified A sound level limit nor exceed the specified indoor noise octave band sound pressure level limit value (The frequency band center frequency is 31.5Hz, 63Hz, 125Hz250Hz, 500Hz, and its coverage frequency is 22Hz-707Hz) It is to take into account that no matter whether it is the noise emitted by fixed equipment of industrial enterprises or the noise emitted by noise sources of social life, they are transmitted through the building structure to noise-sensitive building rooms (referring to hospitals, school institutions, research institutes, and residences that need to keep quiet In buildings, the main component of noise is low frequency characteristics. At this time, the measured A sound level may not exceed the specified limit, but human interference cannot be ignored. Therefore, using only A sound level limits does not guarantee noise sensitivity. In the sound environment quality of buildings in the building, the new standard increases the octave band sound pressure level limit requirements for low frequency bands, and one of these limit values ​​must not be exceeded. It is required to perform octave band spectrum analysis of noise while measuring the A sound level.

The performance and variety of measurement noise monitoring instruments vary widely. Instruments used for environmental noise monitoring should have at least a time-averaged integration function, that is, at least the equivalent continuous sound level Leq, which is sufficient for the environmental supervision department. However, for environmental monitoring stations that require traffic noise measurements or noise surveys, statistical sound level LN (N=5,10,50,90,95) measurements and 24-hour monitoring functions should also be available. In order to reduce manual recording and facilitate further processing of data, it is often necessary to equip micro-printers and transfer data to computers and data storage functions. Considering that there are many low-frequency components in the noise of social life, it is difficult to evaluate its use to humans using only A sound levels. Influence, therefore while measuring A sound level, also should undertake octave frequency spectrum analysis to noise, then use NR curve to measure whether each octave band sound pressure level is within the allowable range. This requires the use of noise spectrum analysis instruments with octave or 1/3 octave filters.

Noise Tester - Principle

The frequency-weighted network in the noise meter has three standard weighted networks: A, B, and C. A network simulates the response of 40 pure tones in the human ear-equivalent curve. Its noise meter curve shape is the opposite of the 340 square equal-intensity curve, so that the middle and low frequency bands of the electrical signal have greater attenuation. The B network simulates the human ear's response to 70-point pure tones, which causes a certain attenuation of the low frequency band of the electrical signal. The C-network simulates the human ear's response to 100-point pure tones and has a nearly flat response over the entire audio frequency range. The sound pressure level measured by the sound level meter through the frequency weighting network is called the sound level. According to the weighting network used, it is called A sound level, B sound level and C sound level respectively. The unit is denoted as dB(A). dB(B) and dB(C). At present, the sound level meter for measuring noise, the head response can be divided into four types according to sensitivity:

1, "slow." The head time constant is 1000ms, which is used to measure the steady-state noise. The measured value is a valid value.

2, "fast." The head time constant is 125ms. It is generally used to measure fluctuations in unstable noise and traffic noise. The fast approach is close to the response of the human ear to the sound.

3, "pulse or pulse hold." The rise time of the hands is 35ms. It is used to measure pulse noise with long duration, such as punch press, hammer press, etc. The measured value is the maximum effective value.

4, "peak hold." The hand rise time is less than 20ms. Used to measure pulse sounds with very short duration, such as guns, cannons, and explosions. The measured value is the peak value, the maximum value.

The sound level meter can use external filters and recorders to perform spectrum analysis on the noise. The domestically produced ND2 precision sound level meter incorporates a frequency-doubled page range filter that is easy to carry to the field and for spectrum analysis. Sound level meter can be divided into precision sound level meter and ordinary sound level meter according to precision. The measurement error of a precision sound level meter is approximately 1 dB of soil, and that of an ordinary sound level meter is approximately 3 dB. Sound Level Meters can be categorized into two categories according to their purpose: one for measuring steady-state noise, and one for measuring unsteady and impulsive noise. An integral sound level meter is used to measure the equivalent sound level of an unsteady noise over a period of time. The noise dosimeter is also an integral sound level meter that is mainly used to measure noise exposure. A pulsed sound level meter is used to measure impulse noise. This sound level meter complies with the response of human ear to impulse sound and the average time of human ear to impulse response.

Noise Meter - Precautions

1. Read the instruction manual before use to understand how to use the instrument and precautions.

2, install the battery or external power supply to pay attention to polarity, do not reverse connection. Do not remove the battery for a long period of time so as not to damage the instrument.

3. Do not disassemble the microphone to prevent it from throwing and place it properly when not in use.

4, the instrument should avoid placing in high temperature, humidity, sewage, dust and hydrochloric acid, high alkali content of air or chemical gases.

5. Do not disassemble the instrument without authorization. If the instrument is not normal, it can be sent to the repair unit or the factory for inspection.

6, the noise meter pay attention to waterproof, prevent falling from high altitude.