What are the differences between the static and dynamic ranges of sound level meters
1. Sound level frequency weighting
The basic definition of sound level meter frequency meter weight refers to the difference specified as a frequency function between its constant amplitude steady-state sinusoidal input signal level and the indicated signal level on the display device. The frequency meter weight is expressed in decibels (dB). The frequency weighting of a sound level meter usually includes A, B, C, and D weighting, which is a different weighting network designed within the circuit of the sound level meter to simulate the different sensitivities of human auditory perception at different frequencies. The sound pressure level measured through a weighted network is called the weighted sound pressure level, such as the A-weighted sound pressure level, also known as the A-weighted sound level; Those that do not pass through a weighted network are called linear sound pressure levels, which are currently represented by Z-weighted sound pressure levels.
A. B and C weights approximately simulate three equal noise curves, namely, 40 square, 70 square, and 100 square. Due to the fact that A weight can better characterize the subjective characteristics of the human ear, A weight sound level is commonly used in noise measurement to represent the size of noise. C weight sound pressure level and Z weight sound pressure level are often represented as total sound pressure level in noise measurement, while D weight is specifically used for aircraft noise measurement.
There are three types of frequency weighting networks in sound level meters: A, B, and C.
The A network simulates the response of the human ear to a 40 square pure tone in the equivalent response curve. Its curve shape is opposite to the 340 square equivalent response curve, resulting in significant attenuation in the middle and low frequency bands of the electrical signal.
The B-network simulates the response of the human ear to 70 square pure tones, which attenuates the low-frequency range of electrical signals to a certain extent.
The C network simulates the response of the human ear to 100 square pure tones, with a nearly flat response throughout the entire audio frequency range.
The sound pressure level measured by the sound level meter through a frequency weighting network is called the sound level. Depending on the weighting network used, it is called the A sound level, B sound level, and C sound level, with units recorded as dB (A), dB (B), and dB (C). At present, the sound level meters used for measuring noise can be divided into three types based on sensitivity:
(1) Slow. The time constant of the meter head is 1000 ms, usually used for measuring steady-state noise, and the measured value is the effective value.
(2) Quick. The time constant of the meter head is 125ms, which is generally used to measure unstable noise and transportation noise with significant fluctuations. The fast gear approaches the human ear's response to sound.
(3) Pulse or pulse hold. The rise time of the watch needle is 35ms, used to measure pulse noise with a longer duration, such as punching machines, press hammers, etc. The measured value is the maximum effective value.
(4) Peak Hold. The rising time of the watch needle is less than 20ms. It is used to measure pulse sounds with a short duration, such as guns, guns, and explosions. The measured value is the peak value. That is the maximum value.
2. Polarized capacitive microphone, sensor
Classification of microphones
According to the principle of sound electricity conversion, it can be divided into electric type (dynamic coil type, aluminum strip type), capacitive type (DC polarized type), piezoelectric type (crystal type, ceramic type), as well as electromagnetic type, carbon particle type, semiconductor type, etc.
There are two types of condenser microphones, one is microphone type, such as those in KTV. This type of condenser microphone uses a battery powered handheld condenser microphone, usually with a No. 5 battery; Another type of condenser microphone is a recording microphone, such as in radio studios and recording studios, which requires a 48 volt phantom power supply.
