Basics & Different Types of Sound Level Meters
Sound Level Meter Basics
Sound level meter, also known as noise meter, is an instrument that measures the sound pressure level or sound level of sound according to certain frequency weighting and time weighting. It is the most basic and most commonly used instrument in acoustic measurement. The sound level meter can be used for the measurement of environmental noise, machine noise, vehicle noise and other kinds of noise, as well as for electrical and architectural acoustics measurements. Vibration is measured using a sound level meter.
Sound level meter is the most basic instrument in noise measurement. The sound level meter is generally composed of a condenser microphone, a preamplifier, an attenuator, an amplifier, a frequency weighting network, and an RMS indicator. The working principle of the sound level meter is: the microphone converts the sound into an electrical signal, and then the preamplifier transforms the impedance to match the microphone and the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting on the signal (or external filter), and then amplifies the signal to a certain amplitude through the attenuator and amplifier, and sends it to the rms detector (or external power supply). flat recorder), the value of the noise sound level is given on the indicator head.
The sound level meter adopts advanced digital detection technology, which greatly improves the stability and reliability of the instrument. The sound level meter has the advantages of simple operation and convenient use, and has the characteristics of large dynamic range, large-screen LCD digital display, automatic measurement and storage of various data and so on.
Sound Level Meter Applications
The sound level meter is widely used in industrial noise measurement and environmental noise measurement of various machines, vehicles, ships, electrical appliances, etc. field of acoustic testing.
How to Classify Sound Level Meters?
According to the sensitivity of the whole sound level meter, there are two types of sound level meters: one is the ordinary sound level meter, which does not require too much of the microphone. The dynamic range and the flat frequency response range are relatively narrow, and the band-pass filter is generally not configured; the other is the precision sound level meter, whose microphone requires wide frequency response, high sensitivity, and long-term stability.
It has good quality and can be used in conjunction with various band-pass filters. The output of the amplifier can be directly connected with a level recorder and a tape recorder, and the noise signal can be displayed or stored. If the microphone of the precision sound level meter is removed and replaced with an input converter and an accelerometer is connected, it becomes a vibration meter and can be used for vibration measurement. In recent years, some people have divided the sound level score into four categories, namely type 0, type 1, type 2 and type 3. Their accuracies are +0.4 dB, +0.7 dB, +1.0 dB and +1.5 dB respectively.
The frequency weighting network in the sound level meter has three standard weighting networks, A, B, and C. The A network simulates the response of a person taking a 40-square pure tone in the equal-loudness curve. Its curve shape is opposite to the 340-square equal-loudness curve, so that the middle and low frequency bands of the electrical signal have greater attenuation. The B network is the response of the simulated person to the 70-square pure tone, which makes the low frequency band of the electrical signal attenuate to a certain extent. The C network simulates the human response to a 100-square pure tone, with a nearly flat response over the entire 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 different weighting network used, it is called the A sound level, the B sound level and the C sound level, and the unit is denoted as dB(A), dB(B), and dB(C).
At present, for the sound level meter used for measuring noise, the response of the meter head can be divided into four types according to the sensitivity:
- "Slow". The time constant of the meter head is 1000 ms, which is generally used to measure steady-state noise, and the measured value is the effective value.
- "Fast". The time constant of the meter head is 125ms, which is generally used to measure unsteady noise and traffic noise with large fluctuations. Fast gear is close to the human response to sound.
- "Pulse or pulse hold". The rise time of the needle is 35ms, and the measured value is the maximum effective value when measuring the pulse noise with a long duration, such as a punch, a hammer, etc.
- "Peak Hold". The rise time of the needle is less than 20ms. It is used to measure pulse sounds with short duration, such as guns, guns and explosions. The measured value is the peak value, that is, the maximum value.
3 Common Types of Sound Level Meters
Integral sound level meter
It can directly display the equivalent continuous level of the measured noise within a certain measurement time in digital form. For non-steady noise, it is required to measure the equivalent continuous sound level Leq of the noise, with an A sound level to represent the noise level in this period of time.
Digital sound level meter
The sound level meter with digital display of measurement results not only has the advantages of intuitive and accurate reading, but also can be processed with other analysis and processing instruments and computers through BCD code output.
Pulse sound level meter
The effective value of the measured signal is measured by the pulsation characteristics of the capacitor at different times, and it has a high crest factor capacity, so it can respond to the pulse sound with a short duration and a low repetition ratio. In our daily life, we often encounter discontinuous noise, that is, impulse sound or impact sound, such as typewriter noise, punching bed and so on. The duration of this noise is very short, the pit viper may appear for a long time, and even only appear once in a certain period of time. To measure with a general sound level meter, there will be a large error, and a pulse sound level meter should be used.
ATO sound level meter has the characteristics of large dynamic range, large LCD digital display, GPS positioning, automatic measurement and storage of various data, etc. The measurement range can be selected from 40~130 dB, 45~160 dB, and 20~143 dB.
