A pulse sound level meter is a precision acoustic measurement instrument specifically designed to measure non-stationary, discontinuous pulse or impulse sounds. Its principle can be analyzed from four aspects: core components, signal processing flow, time and frequency weighting, and special function design
1、 Core components
Microphone: converts sound waves (pressure changes) into weak analog electrical signals. Pulse sound level meters usually use capacitive microphones, which are suitable for capturing rapidly changing pulse sounds due to their high accuracy and wide frequency response.
Pre amplifier: Enhances the weak signal strength output by the microphone to ensure that the signal is not distorted during subsequent processing.
Signal processor: performs frequency weighting and time weighting processing on signals, simulating the perceptual characteristics of the human ear towards sound.
Display screen: displays measurement results, usually in decibels (dB).
2、 Signal processing flow
Acoustic electric conversion: A microphone converts sound waves into electrical signals.
Signal enhancement: The preamplifier enhances the electrical signal to increase its strength.
Frequency weighting: Simulating the sensitivity of the human ear to sounds of different frequencies through a frequency weighting filter. A weighted network simulates the response of the human ear at moderate sound levels, weakening low-frequency components; The C-weighted network retains more low-frequency components and is suitable for evaluating peak high sound pressure levels.
Time weighting: Integrating signals over time to reflect the rate of change in sound energy. The pulse sound level meter adopts specific time weighting characteristics, such as pulse time weighting, and its exponential averaging circuit has a time constant of 35ms for both charging and discharging, which can accurately capture the peak value of pulse sound.
Detection and display: The detector converts the AC signal into a DC signal and displays the sound pressure level value on the indicator head. Pulse sound level meters usually have peak hold function, which can keep the measurement results on the indicator for a sufficient period of time for reading observation.
3、 Time and frequency weighting
Time weighting: The pulse sound level meter adopts the pulse time weighting characteristic, with a short rise time constant and a long decay time constant, which can accurately capture the peak value of pulse sound and maintain it for a sufficient period of time.
Frequency weighting: Simulate the sensitivity of the human ear to different frequencies of sound through a frequency weighting filter, making the measurement results more in line with human perception. A-weighted network is a widely used frequency weighting method, suitable for noise measurement in most environments and workplaces.
4、 Special function design
Pulse holding function: It can hold the measurement results on the indicator for a sufficient amount of time (such as more than 1 minute) for reading observation.
Peak holding function: For short duration pulse sounds (such as gunshots, explosions), the pulse sound level meter can measure their maximum peak value and hold the result for a sufficient amount of time.
High dynamic range: The pulse sound level meter has a wide dynamic range and can measure various pulse sounds from weak to strong.