Purchase instructions: 1.The product is powered by 12V DC,Product has no battery, it uses AC power supply. 2.Usually in a very quiet room, the value will not be lower than 40dB, which is normal. Description: Large digital LED display Measurement range is 30 ~ 130dB The meter can be hangged on the wall. Specifications: Model: EU-N0725. Measurement range : 30 ~ 130dB (dB). Accuracy: +1.5 dB (reference sound pressure level, 94dB @ 1kHz). Frequency response: 31.5Hz ~ 8.5kHz frequency weighting: A and C. Response time: Slow or Fast. Power supply: DC 12V 1A DC5521. 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. Package Included: 1 x EU-N0725 sound level meter, 1 x Power supply,1 x Manual.