This decibel meter is applicable for the measurement of noise engineering, quality control, health prevention, treatment and various environmental noises. But it is account for the relative loudness perceived by the human ear.The value will fluctuate according to the different distance sound source. Specifications: Sound pressure accuracy: 1.5 dB (sound pressure standard, 94 dB @ 1KHz). Sound pressure accuracy: 5 dB (sound pressure standard, 94 dB @ 8KHz). Sound pressure frequency response: 30Hz - 8KHz. Dynamic range of sound pressure: 50 dB (for each measurement gear level). Sound pressure measurement scope: 30-130 dBA, 35-130 dBC. Sound pressure frequency weighting characteristics: A and C characteristics. Dynamic characteristic of sound pressure: FAST 125ms, SLOW 1sec Microphone: polarized capacitive microphone. Digital display: 4-digit, resolution: 0.1 dB, sampling rate: 2 times/sec. Analog bar display: Each analog bar represents 1 dB, sampling rate is 20 times/sec. Measurement gear level: 30-80 dB, 40-90 dB, 50-100 dB, 60-110 dB, 70-120 dB, 80-130 dB, 6 gear levels in total. Below or above limit prompt: indicated with UNDER or OVER display. Power supply:4 AAA batteries 1.5V Package list: 1 * Sound Level Meter(Batteries not include) 1 * User Manual Note: 1.Do not use the meter in hot,humid environment. 2.If the meter is not to be used for a long time, remove the batteries to avoid electrolyte leakage damaging instrument. 3.If you want to calibrate it , it needs Primary standard acoustic source, acoustic environment,Normally only the third testing organization or the credited laboratory could do it. The Mini Handhold Digital Sound Level Reader is compact, lightweight,easy to use,it is not only extremely wear-resisting, but also elegant Features with backlight feature,it is appropriate for gathering the sound date at night. And backlight auto power off function is provided, high-reliability and well-designed high-efficiency power supply circuit make the battery more durable This Audio DB Meter complies with IEC651 Type 2 and ANSI S1.4 Type 2,with the measuring scope from 30 to 130 dB and automatic shifting function, A and C Frequency Weighting mode selection. With Maximum(MAX) locking function and High speed(FAST)/Low speed(SLOW) response rate selection It could be called as DB reader, phonometer or SPL meter,accumulate sound level value data for noise dosimeter, can be used as a noise monitor testing sound intensity to reduce Noise pollution,avoiding the risk to hearing damage The Noise Level Meter is an instrument used to measure the ambient sound level,such as sound level around factories, workshops, schools, residential, offices, road, audio etc.It also can be appropriate for noise engineering,product quality control,health prevention and treatment,etc