... octave digital filters Environmental noise measurement and 24 hour monitoring Reverberation time measurements Airport Noise Monitoring and data ... s, LAeq, T, LAE, LAFeqT.24 hours monitors menu :And Ld, Ln, Ldn22Real-time spectrum analysisFulfils standards: IEC 61260 Class 1Filter ... rechargeable batteries, which can work for over 12 hours continuously. 9 V external power supply is also ...