Sound level meter time weighting
In real life, there are many types of noise, including steady-state noise, transient noise, and impulse noise. Time weighting is introduced for different noise measurements. Time weighting is actually a time average of the measured signal. Usually, the time average characteristics include four modes, namely "Fast" gear, "Slow" gear, "Impulse" gear and "Peak" gear.
(1) For continuous sound signals, the "fast" gear and the "slow" gear are usually used for weighting. The weighting time constant of the "fast" gear is 125ms, which is generally used to measure unstable noise and transportation noise with large fluctuations. Fast gears are close to how the human ear responds to sound. The "slow" gear weighting time constant is 1000ms, which is generally used to measure steady-state noise, and the measured value is the effective value. For steady-state continuous sound signals, there is no significant difference between the two weighting methods. However, if the measured sound fluctuates greatly and the weighting time is different, the results obtained by using the "slow gear" weighting will be more stable. However, due to the long averaging time, errors will occur in peak and peak to valley measurements. Therefore, in order to accurately understand the real-time changes in the signal, it is appropriate to use the "fast" weighting (the fast speed is close to the human ear's response to sound, and the fast speed and A weighting should be used when measuring the background noise in a soundproof room).
(2) The time constant of the "pulse" gear is 35ms, which is used to measure long-duration pulse noise, such as punches, hammers, etc. The measured value is the maximum effective value. The time constant of "peak hold" is less than 20ms and is used to measure short-duration pulse sounds, such as guns, cannons and explosions. The measured value is the peak value, which is the maximum value.
Time weighting is usually used in sound level meter measurements, and only when time weighting is used in conjunction with the previous frequency weighting can the measurement results reflect the subjective feeling characteristics of the human ear to a certain extent. In addition, the sound level meter can be connected to an external filter and recorder to conduct spectrum analysis of the noise.
