Purchase instructions:This product doesn't have a battery. It only works with alternating current. The product is powered by USB cable, please confirm before purchase, you have USB socket applicableUsually in a very quiet room, the value will not be lower than 40dB, which is normal. Description: 18”Large Display Digital LCD Display Measurement range is 30 ~ 130dB The indicator light blinks and buzzer Alarm Use the device to measure noises inside or outside. With hanging holes, can be hangged on the wall Specifications: Measurement range : 30 ~ 130dB (dB) Accuracy: +1.5 dB (reference sound pressure level, 94dB @ 1kHz) Frequency response: 31.5Hz ~ 8.5kHz frequency weighting: A Response time: Fast Microphone: 6mm condenser microphone Power supply: 5V 2A DC micro USB power supply working environment: 0 - 40 degrees (32 degrees Fahrenheit to 104 degrees Fahrenheit), 10 - 80%RH Storage of Temp. and humidity: -10~60C. 10~70%RH LED light color:Red Dimension:400*230*34.5mm(15.72*9.04*1.36in) Weight:1442g Package Included: 1 x SW-526A sound level meter 1 x USB cable​ 1 x Manual Model: SW-526A Brand: TestHelper